Method and apparatus for selective irradiation of biological materials

Abstract: The invention relates to a method and an apparatus for frequency selective irradiation of biological materials and particularly tissues, cells and/or cell components of living organisms, in particular of human and animals, by irradiating a component element of the target material at the corresponding Mössbauer absorption frequency. The component radiation absorption at the Mössbauer absorption frequency is thus enhanced many times over the absorption of the surrounding material having a different Mössbauer absorption frequency. The energy thusly absorbed by the target material component is converted to and remitted as Auger electrons, which provide intranuclear radiation resulting in lethal double strand breaks in the DNA molecules of the target tissue. The irradiation is ad­ ministered in frequency and material selective modes of treatment, and may be combined with conventional chemo­ therapeutic agents to provide a further enhanced treatment modality. Moreover, the source frequency can be adjusted to enhance the killing effect. The method of apparatus according to the present invention are useful in combination with naturally occurring or administered pharmaceutical stable isotope absorbers, having significantly reduced side effects by comparison to conventional chemotherapy or radiation therapy. The method and apparatus according to the invention can be applied for selective radiation therapy providing selective tissue damage or necrosis, in particular for cancer therapy, and for differentiating between diseased and normal tissues.

Description: The present invention relates to a method and a combination of a Mößbauer type apparatus and a Mößbauer absorber for the selective, specific irradiation of biological materials and particularly of tissues and cells of living organisms, in particular of human and animals, and of cell components, with radiation of selective frequency. Besides from non-therapeutical applications the method and apparatus combination according to the invention are optimally suited also for frequency selective radiation therapy for cancer. In the treatment of tumors by ionizing radiation, x-rays or gamma rays are particularly used. The ideal in radiation therapy of malignant disease is achieved when the tumor is completely eradicated and the surrounding normal tissue, in the treated volume, shows little or no evidence of structural or functional injury. The important factor in successful treatment is the difference in radiosensitivity of neoplastic and normal cells. All tissues, normal end neoplastic, are effected by radiation so that radiosensitivity is a relative term. The basis of radiation therapy is that cells that are actively proliferating or that are of a primitive type are more sensitive than normal tissue so that there is usually a considerable margin between doses that are damaging to neoplastic end to normal cells. The difference depends on the capacity for intracellular repair of normal end neoplastic cells and the ability of normal organs to continue to function well if they are only segmentally damaged. If surrounding tissue can tolerate twice the radiation dose of a given tumor, then the tumor is radiosensitive. Mammalian cells are capable of accumulating radiation damage before they are killed exponentially. Also, if allowed sufficient time after exposure, mammalian cells are capable repairing sublethal and potentially lethal radiation damage. The effects of x-rays or gamma rays on growing cells vary with intensity and duration of exposure and consist of destruction of some cells, inhibition of imminent mitosis, followed by abnormal mitosis and disruption of the cells and damage to resting cells so that continued proliferation fails. The prime target of present radiotherapy is the DNA molecule of a cell which does not select for cancer cells but selects for DNA repair capabilities. Even a two-to-one increase in radiation sensitivity in cancer cells will result in a curable condition. However, normal surrounding tissue may not be more tolerant to x-ray therapy than cancer tissue which makes this therapeutic modality useless. Mößbauer absorption, which is the resonant absorption of gamma rays by nuclei, represents a method of increasing the radiosensitivity of tumors in terms of orders of magnitude via selective energy deposition in cancer cells. Mößbauer radiation is completely analogous to optical absorption. In the latter, the ultimate source of radiation consists of excited atoms or molecules which decay to the ground state. The radiation after being suitably monochromatized by a prism or diffraction grating is incident upon the sample and the intensity of the beam which is transmitted through the sample (absorber) varies as a function of the frequency as photons of energy equivalent to electronic, vibrational, rotational, and translational transitions are absorbed. In Mossbauer absorption, the source comprises excited nuclei which in decaying to their ground state emit gamma radiation; with certain nuclei in appropriate surroundings, such as exist in a crystal lattice, the radiation is highly monochromatic. In fact, the gammy-ray line can be so narrow that its frequency may be shifted significantly by incorporating the source or absorber in a mass driver oscillating at moderate velocities to produce a Doppler effect. The frequency of the mass driver which provides a Doppler shift to the gamma ray photons functions analogously to the dispersion device in optical absorption. By varying the driving frequency, a resonance system can be driven by the emitted gamma photons and the nuclear energy transitions of the sample (absorber). The absorber may occur naturally, or as in the preferred embodiment, comprise added stable pharmaceutical isotopes, discussed below. Furthermore, since it has been determined that cancer cells differ from normal cells with respect to level of aerobic versus anaerobic metabolism, internal concentrations of ions such as Ca²⁺ and Mg²⁺, pH, spin lattice relaxation times, and resting membrane potentials, it is believed that such differences would cause differences in the nuclear microenvironment in cancer cells versus normal cells significant enough to result in excitation energy differences on the order of 10⁻⁶ eV. Such excitation differences will affect Mößbauer absorption, and would allow for selective targeting of cancer cells, for example, exposing malignant tissue with an ⁵⁷Fe absorber to a narrow line width beam of 14.4 keV photons having a photon energy equal to the ⁵⁷Fe nuclear transition of cytochrome c (in this tissue), which is different from normal tissue transition and therefore represents a powerful treatment modality. US 3 257 558 relates to a method and a device for selectively detecting radiation, including gamma rays due to the Mößbauer effect. This document does not teach nor suggest a method or an apparatus for the selective irradiation of biological target materials. It is the object of the present invention to provide a method and an apparatus for the selective irradiation of biological materials, the apparatus being suitable also for applications such as cancer diagnosis and therapy. The above object is achieved according to the independent claims. The dependent claims relate to preferred embodiments. Method The method of the present invention for the selective irradiation of biological materials, particularly of tissues, cells and/or cell components, comprises the following steps: (I) Providing a Mößbauer radiation source selectively emitting γ-radiation of at least one frequency, (II) tuning the frequency of the γ-radiation emitted from the Mößbauer radiation source in accordance with the resonance absorption frequency of a Mößbauer absorber, and (III) irradiating the biological material having incorporated therein the Mößbauer absorber, with Mößbauer resonance absorption of the tuned γ-radiation from the Mößbauer radiation source, the Mößbauer absorber having the corresponding Mößbauer resonance absorption frequency at the specific site where it is localized to provide selective damaging or necrosis of the biological material, methods for the therapeutical and surgical treatment of the human or animal body and diagnostic methods practised on the human or animal body being excluded. In the following, the invention will be further described with reference to the figure, showing one preferred embodiment of the apparatus combination according to the present invention. The most dramatic killing effect of radiation has been shown to be due to intranuclear radiation effects of internal conversion and Auger electrons which result in lethal double stranded breaks in DNA molecules (S.L. Commerford et al., Int. J. Radiat. Biol., 1980, vol. 37, No. 5, 547-554; U. Linz et al., Proceedings of the Seventh International Congress of Radiation Research, July 3-8, 1983, Amsterdam, M. Nijhoff Publishers, The Hague, Presentation 'Chemical and Biological Consequences of the Iodine-125 Decay in DNA'). Internal conversion results in the ejection of inner shell electrons. The difference between the ionization energy of the inner shell electron and that of the outer shell is released either in the form of a fluorescence x-ray photon or is transmitted to another electron which is then ejected as an Auger electron. The process continues, shell by shell, until the valence shell is reached and thus leads to multiple ionizations of the atom. Such a valency cascade is known as the Auger effect. For elements of low or medium atomic number, the Auger electrons have energies up to a few keV with a relatively high linear energy transfer (LET) of 1 to 10 eV/nm. Since such electrons dissipate their energy in materials of unit density within a distance of the order of 10 to 100 nm, they may efficiently damage molecules in the nearness of the decay event. Mößbauer absorption depends on the microelectronic environment of the nucleus. The energies of the nuclear transitions of the absorber are dependent on the s electron density, electric field gradient, and effective magnetic field at the position of the nucleus in which resonant gamma ray absorption occurs. For example, resonant absorption of iron is affected by the bonding in the iron ligand complex and factors which affect this bonding such as pH, ionic strength, ionic charge of the central atom, concentration of ions such as Mg²⁺ and Ca²⁺ as well as electric and magnetic fields. Mößbauer nuclei absorb gamma radiation and are excited to a high energy nuclear state. Following recoilless absorption, the predominant mode of decay is by internal conversion. For example, following resonant absorption of the incident gamma ray the excited ¹¹⁹Sn nuclei in the absorber undergo internal conversion 84 percent of the time. In a paper by C.M. Yagnik et al., Nuclear Instrumentation Methods, 114 (1974), page 1, 84; 20 keV internal conversion and 75.3 keV Auger electrons are reemitted for every 100 gamma rays resonantly absorbed. Approximately half of these electrons are emitted in the backward direction, which is not the case with particle radiation. The remainder of excited nuclei re-emit gamma or x-rays. Thus, Mößbauer cancer therapy promises the advantages of selective radionuclides without systemic radiation of normal tissue, higher kill per event secondary to production of Auger electrons, and higher kill per atom due to the fact that once a Mößbauer absorber atom decays it will be re-excited with probability equal to the original excitation event. Momentum and energy are conserved during an emission event. For a free atom of mass m, the recoil energy due to emission of a photon of energy Eo is Eo/2mc², where c is the velocity of light. If the atom is in motion during emission, the photon energy will be modified by a term Eo|v/c| cos σ , where v is the velocity of the atom, and σ is the angle between v and the momentum vector of the photon. The energy of the photons emitted by such atoms is given by (emission) E γ = Eo - Eo/2mc² + Eo|v/c| cos σ (1) where Eo is the photon energy in the rest frame of the nucleus. The photon energy for resonant absorption by a similar nucleus moving with velocity v' and direction σ' is (absorption): E' γ = Eo + Eo/2mc² + Ec|v'/c|cos σ' (2). The energy of gamma rays emitted by a system of free atoms moving with thermal velocities would be centered at Eo - Eo/2mc² while the resonant absorption cross-section would be centered at Eo + Eo/2mc² . Thus, resonant absorption would be expected to occur for the fraction of events represented by the overlap in energy of the emission and absorption lines. The width of this overlap region is of the order of thermal energy: about 10⁻² eV at room temperature. If the atom is in a bound state, a deviation from Equations 1 and 2 is observed. Mößbauer discovered that a certain fraction of gamma rays emitted by ¹⁹¹Ir nuclei in a solid do not obey Equation 1; instead, they had energy equal to Eo and a line width Γ = ℎ/Tm , where Tm is the mean life of the excited state; corresponding effects were observed in absorption. The significant fact is that the emitting (or absorbing) atom is bound to other atoms in a solid. There then exists a certain probability that the recoil momentum associated with the emission (or absorption) of a photon will be taken up by the lattice rather than by the individual atom. When this occurs, the recoil energy Eo/2mc² becomes vanishingly small because m is now essentially the mass of the crystal rather than the mass of a single atom. In addition, the lattice has a discrete set of vibrational transitions. This means that the last term in Equation 1 or 2 is replaced by a quantity which describes the number of phonons that have been interchanged between the lattice and the gamma ray phonons. There is a nonvanishing probability that no photons are exchanged. When these conditions prevail, the emission (or absorption) is described as "recoilless" or "recoil-free", and emitted (or absorbed) photons match very closely the energy and level widths of the nuclear transition. This feature characterizes the Mößbauer effect, which is applied for therapeutic treatment according to the present invention. The probability of a recoilless event (emission or absorption) depends on certain properties of the solid as well as the energy and mean life of the nuclear excited state, the solid need not be crystalline. Mößbauer effects have been observed in amorphous materials and even liquids of high viscosity. If f is the probability of a recoilless event, also known as the Debye-Waller factor, it has been shown that where 〈r²〉 is the square of the displacement of the emitting or absorbing atom from its equilibrium position along the direction of the gamma ray momentum; averaged over the lifetime of the nuclear excited state; λ is the wavelength of the radiation. It can be seen from Equation 3 that f is large when the scattering center is confined to a region small with respect to the wavelength of the radiation involved. 〈r²〉 decreases with increasing lattice binding energy; it also decreases as the temperature is lowered. The Debye-Waller factor f has been calculated for a crystal in which the forces are harmonic, using the Debye model of a solid: in which ϑ is the Debye temperature, m is the atomic mass, k is the Boltzmann constant, and Eo is the gamma ray energy. The recoil energy in the case of ⁵⁷Fe used as an absorber pharmaceutical is 2.10⁻³ eV; this is well below the average vibrational energy at room temperature (∼ 10⁻² eV). The low recoil energy coupled with relatively high Debye temperatures for iron complexes (e.g. ϑ = 355 °C for Fe metal) makes ⁵⁷Fe particularly suitable for Mößbauer absorption. The Debye-Waller factor for ⁵⁷Fe in metallic iron is 0.7 at room temperature. In the low temperature limit It can be seen from Equation 5 that when the free atom recoil energy is less than kσ, which is the average energy of a lattice vibrational mode, a recoil-free event has a high probability of occuring. At 5K, the value of f in oxyhemoglobin has been found experimentally to be 0.83. The recoil energy due to absorption of a 14.4 keV photon by hemoglobin is 2.10⁻⁶eV; the recoil energy of cytochrome c embedded in a protein matrix would be expected to be less: thus, it would more closely approach the line width. The absorption cross-section for a gamma ray to produce a transition between nuclear ground and excited states at resonance followed by internal conversion, is given by where h is Planck's constant, c is the velocity of light; Eo is the transition energy, Ie and Ig are the excited and ground state spins, respectively, and α is the internal conversion coefficient (α describes the relative strength of radiative (gamma ray) and nonradiative (electron conversion) processes connecting the ground and excited states; α = 0 if all the decays from the excited state involve the emission of a gamma ray). The fact that this cross-section is dependent entirely on nuclear parameters is an important and useful feature of the Mößbauer effect. For a single ⁵⁷Fe nucleus, σ o has the value 2.5·10⁻¹⁷ cm² for the 14.4 keV transition. This cross-section is about 10⁷ times larger than the actual geometrical cross-section of the nucleus and is also very large compared to the photoelectric (electronic) absorption cross-section for iron, which is 5.5·10⁻²¹ cm² per atom at this energy. The absorption is an exponential function of the cross-section; thus, the nuclear resonance absorption process is a strong effect. The apparatus - absorber combination The apparatus - absorber combination of the present invention for the selective irradiation of biological materials for carrying out the above-described method, including corresponding methods for the therapeutical and surgical treatment of the human or animal body and diagnostic methods practised on the human or animal body, comprises a Mößbauer absorber adapted to be located at or in the biological material to be irradiated, the apparatus comprising: (A) a Mößbauer radiation source selectively emitting γ-radiation of at least one frequency and (B) tuning means for tuning the frequency of the γ-radiation emitted from the Mößbauer radiation source in accordance with the resonance absorption frequency of said Mößbauer absorber. The Mößbauer absorber is located at or in the biological material to be irradiated, receives the tuned γ-radiation from the tuning means, and has the corresponding Mößbauer resonance absorption frequency at the specific sites where it is localized to provide selective damaging or necrosis of the biological material. The overall operation of the system may be described as follows. The radioactive source in the form of a thin film of nonmagnetic material such as stainless steel, copper, or palladium into which radioactive ⁵⁷Co has been allowed to diffuse produces a beam of highly homogeneous photons having an average energy of 14.4 keV. The homogeneity, or line width ΔE is 4.5·10⁻⁹ eV so that ΔE/E is less than 10⁻¹². A filter selects the 14.4 keV photon from the other two photons of different energy. By mounting the source on an accurately controlled mass drive, the energy of the photon is shifted by means of the Doppler effect. A velocity of 1 mm/s corresponds to an energy change of 4.8·10⁻⁸ eV or more than ten line widths. A wide variety of velocity drives exist. The arrangement 100 shown in the Figure is one in which the source 50 is mounted on a cone 62 of a speaker 60 and the speaker is driven so that the velocity increases and decreases linearly with time (symmetric triangular wave form) at approximately 5 Hz. Since the displacement of the speaker coil is quite closely proportional to the input voltage, it is necessary to provide a ramp voltage in order to produce a constant velocity. This is accomplished by a triangular wave. A function generator 54 is employed to produce an accurate, low frequency triangular voltage. This voltage is applied to the speaker 60 through a power amplifier 56. In practice, it is necessary to employ considerable negative feedback to produce an accurately constant velocity. This is accomplished by coupling a second or using a double voice coil 64 speaker 66 to the drive speaker 60 with a rigid rod 52 and providing the error signal from the second speaker monitored by oscilloscope 58 to the amplifier 56 through the integrator 68 as shown schematically in Fig. 1. The source 50 is mounted on the rod connecting the two speakers. Since the source executes two velocity excursions, one at positive and one at negative accelerations, a synchronized shutter 70 can be used to block radiation during the nonresonant excursion. The source, or emitter of radiation, can also include the techniques known to Mößbauer spectrometry, with the addition of a single frequency filter 80. The filter 80 receives source 50 radiation through an input collimator 82 which enters a diffraction crystal 84. Since the diffraction angle can be calculated (Bragg equation n-λ = 2d sin ϑ ), the desired frequency is selected by placement of an output collimator 86 and the selection of a crystal having an appropriate intranuclear layer distance (d). In addition to the above-mentioned photon sources, the photon emitters of Table 1 listed further below are useful in conjunction with absorbers having the corresponding absorption frequencies. Fluorescence, or nuclear emissions of the excited components of the irradiated materials, particulary a tissue, at the Mößbauer frequency can also be observed from the target area. The dynamic range (signal-to-noise) can be enhanced by viewing the subject 90 off-axis from the incident radiation from the source, thereby eliminating the background level (from the source). Off-axis viewing is possible due to the nondirectional characteristic of the fluorescence of the target tissue component at the Mößbauer frequency. Moreover, the frequency of the fluorescence will coincide with the frequency of the source due to the narrow spectrum of the Mößbauer resonance. Furthermore, the fluorescence can be continuously monitored by sensor 92 to give a characteristic plot of the treatment effectiveness. A control signal can be derived from such fluorescence, and combined or processed by processor 94 according to the characteristic plot to continuously control the source to optimize the therapy treatment. Image scanning All Mößbauer isotopes are gamma emitters following absorption of the same energy gamma photon, and most are stable isotopes; therefore, they can be used in scintiscan methods. As in the case of radionuclides, information can be gained based on differential uptake, excretion, or concentration as a consequence of the physiology of the pathological process. But Mößbauer scintiscans also provide the ability to diagnose disease processes and to selectively image different tissues based on the phenomenon of the differential resonance frequency of the absorber isotope in different tissue environments. Exciting the absorber isotope or isotopes by causing a selected Doppler shifted emission from the emitter or emitters along one axis and simultaneously scanning with conventional scintiscan instrumentation along an axis different from the former axis produces a MIRAGE (Mößbauer Isotoping Resonant Absorption of Gamma Emission) scintiscan. Due to attenuation of the exciting beam as a function of distance along the emitting axis, a correction algorithm has to be used to process the data to produce an image of the actual distribution of the Mößbauer isotope or isotopes in the tissue. Radionuclides, which have short half lives, on the order of hours, and which are gamma-emitting isotopes, are used in scintiscans to gain diagnostic information based on the physiological properties of the pathological process. These properties include differential uptake, concentration, or excretion of the radionucleotide by normal versus diseased tissue. For example, hepatic scintiscans are performed with gamma-emitting isotopes that are extracted selectively by the liver, followed by external radiation scanning of the upper abdomen. There are basically three types of liver scans: The colloidal scan, which depends on uptake of labelled colloid by Kupfer cells, where ¹⁹⁸Au colloidal gold or 99m Tc sulfur colloid is most commonly used; the HIDA or PIPIDA scans ( 99m Tc-labelled N-substituted iminoacetic acids) in which the dye is taken up and excreted by hepatocytes, and the gallium scan, in which the radionuclide ⁶⁷Ga is concentrated in neoplastic or inflammatory cells to a greater degree than in hepatocytes. Hence, a hepatoma or liver abscess will produce an area of reduced uptake or "hole" using colloid or HIDA or PIPIDA scans, but there will be an area of increased uptake or "hot spot" with a gallium scan. The gallium scan is also helpful in diagnosing neoplastic infiltration in the patient with cirrhosis, since the tumor will show increased uptake, while fibrous bands will show decreased uptake. Another major application of HIDA or PIPIDA liver scans is in the diagnosis of acute cholecystitis, where failure of the nuclide to enter the gall bladder is considered evidence of cystic duct or common bile duct obstruction. The normal physiology involved is the stake of these compounds by the hepatocytes followed by excretion into the biliary canaliculi and concentration in the gall bladder. Pharmaceuticals, active ingredients and compositions A number of pharmaceutically suited isotopes or compounds comprising these isotopes show the Mößbauer effect and a change of absorption frequency in tissue. The stable isotope ⁵⁷Fe demonstrates this effect; thus cytochrome c which contains Fe can be selected as a target for Mößbauer absorption. Cytochrome c is a heme protein found in the mitochondria of mammalian cells. It constitutes about 1 wt% of mitochondrial protein (Journal of Bioenergetics and Biomembranes, 1984, vol. 16, No. 5/6, 428-431), and is involved in the respiration of aerobic organisms and tissues. It has a relative molecular mass between 12,000 and 13,000 and one heme group per molecule. At least three bonds link the heme to the protein in cytochrome c; one is thought to be an iron-protein bond, and two are covalent bonds to the porphyrin ring. To obtain ⁵⁷Fe in the proper excited state it is necessary to use the radioactive isotope ⁵⁷Co which decays with a half life of 270 d, to the 136 keV excited state of ⁵⁷Fe; the latter nucleus in decaying to its own ground state emits three gamma rays, one of which has an energy of 14.4 keV which has the characteristics suitable for Mößbauer absorption. In ⁵⁷Fe, the 14.4 keV level has a mean life of 1.0·10⁻⁷ s of a line width of 4.5·10⁻⁹ eV, so that when ⁵⁷Co is embedded in a nonmagnetic solid, the 14.4 keV photons have a special homogeneity (ratio of line width to gamma ray energy) of three parts in 10⁻¹³. As a consequence, hyperfine interactions as small as 10⁻⁸ eV become accessible to selective absorption by Mößbauer effects. Furthermore. cytochrome c is strongly bound to a heavy molecule which is embedded in a protein matrix and thus is accessible as a target by this effect. Furthermore, iron occurs in a distinct environment (or prosthetic group) in several molecules, e.g., the heme group occurs in hemoglobin, myoglobin, peroxidases, and catalases as well as in cytochromes. In addition, many biological molecules contain Fe at their active centers. Thus, the potential of using this isoptope as a target of therapy is not limited to cytochromes. For example, spectra of red blood cells demonstrate that the absorption spectrum of deoxyhemoglobin is significantly different from that of oxyhemoglobin. This property may be used to treat large tumors which have outgrown their blood supply and are therefore ischemic. By irradiating at the deox Hb Doppler frequency, the gamma rays would be selectively absorbed by red blood cells present in vessels supplying the tumor. Coagulation secondary to damage to those cells would result in thrombosis of the blood supply to the tumor and concomitant tumor death. ⁵⁷Fe occurs with a natural abundance of 2.2%. Furthermore, the total body iron stores are about 4 g and the turnover rate is about 1 mg/d. Patients who consume ⁵⁷Fe would incorporate this isotope in cells which have a rapid turnover rate. Cancer cells would be enriched relative to normal cells. Many other stable isotopes demonstrate recoilless absorption of gamma ray photons following recoilless emission from the corresponding decaying isotope. The absorber isotopes appear in Table 1. The isotopes ⁵⁷Fe, ⁸³Kr, ¹¹⁹Sn, and ¹⁶²Dy have large Mößbauer cross-sections and isotopes of Fe, Sn, Sb, I, Eu, and Dy are, in particular, very suitable for cancer pharmaceuticals. These Mößbauer isotopes could be used to replace the same element, e.g., ¹²⁷I and ¹²⁹I could be used in hormones or ⁶⁷Zn in enzymes. Also, Mößbauer isotopes could be used to substitute for a different element, e.g., ¹³³Cs could be substituted for Na⁺ and K⁺, or ¹⁵¹Eu as ¹⁵¹Eu²⁺ could be used as a substitute for Ca²⁺ in bone. Furthermore, many possibilities exist for developing pharmaceuticals which exploit the properties of cellular structures of molecules to cause differential binding of a Mößbauer atom or molecule incorporating one or more Mößbauer atoms to selected sites in the tumor cells. Large local concentrations could be achieved through this process. ¹¹⁹Sn²⁺ is a candidate for binding to DNA, which is negatively charged. For ¹¹⁹Sn, 119m Sn could be incorporated into a BaSnO₃ matrix to constitute the emitter. A Pd filter would remove β-particles, and the pharmaceutical could be a salt of ¹¹⁹Sn²⁺. ¹³¹Xe or ¹²⁹Xe which are membrane-soluble could be used to localize into the nuclear, mitochondrial or cellular membrane. Furthermore, experiments have shown that molecules or atoms which are dissolved into membranes or bound or absorbed to cellular structures undergo recoilless absorption. (E.H.Evans et al., The Biochemical Journal, 1977, vol. 166, 547-551; E. Giberman et al., Journal de Physique vol. 35 (1974) C6, 371-374). Tissue selective therapy Bone tumors and bone metastases can be treated by the incorporation of a Mößbauer absorber into bone. Recoilless absorption will occur when the isotope becomes part of the bone matrix. Emission Mößbauer nuclide for ¹³³Cs is ¹³³Ba. J.H. Marshall, Phys. Med. Biol. 13 (1968), p. 15, has obtained a Mößbauer spectrum with a ¹³³CsF absorber and a source provided by ¹³³Ba fixed onto bone powder by incubation of the latter in a solution of radioactive ¹³³BaCl₂. In addition to the alkaline earths, the rare earths are also "bone seekers" (C. Kellershohn et al., Proceedings of the 18th Ampère Congress, Nottingham, 1974, 289-290; C.Kellershohn et al., Journal de Physique Vol. 40 (1979) C2-505) have investigated both in vivo and in vitro fixation of rare earths onto bone material using ¹⁶¹Dy Mößbauer spectroscopy. Excellent spectra are obtained at room temperature indicating that the rare earth element is metabolically fixed onto the bone and is actually incorporated into a solid structure. Another pharmaceutical is ¹⁵¹Eu or ¹⁵³Eu since both atoms can be isoelectronic with Ca²⁺. ¹⁴⁹Sm has a very significant Mößbauer cross-section of 3.7·10⁻¹⁸, and ¹⁴⁹Sm and ¹⁵³Sm are also rare earth "bone seeking" candidates for the metabolic incorporation at sites of new bone formation secondary to metastatic or primary bone cancer. Also, pharmaceuticals, active ingredients and corresponding compositions, could be synthesized using these isotopes such that the Mößbauer absorption occurs at a Doppler frequency in the cancer cells which is different from that of normal cells. The difference in chemical environments between normal and cancer cells results in alternate conformation, protonation, charge, etc. of the properly constructed therapeutic molecule so that the s electron density at the Mößbauer nucleus is altered. The difference in s electron density results in a difference in the nuclear transition energy with a concomitant frequency difference of absorbed photons. Energy/frequency selective therapy The Mößbauer absorption spectrum of a biopsy material of normal and malignant tissue would yield the Doppler shifted frequencies that would result in selective gamma ray absorption in the malignant tissue. The apparatus and methods according to the present invention also select the source frequency to optimize the cell demage or kill when different from the actual Mößbauer absorption of the target tissue. The photoelectric and Compton cross-sections are summarized in Table 2 which contains the mass energy absorption coefficients in the absence of the Mössbauer effects. The equation for determining the total dose from gamma ray treatment and the depth of penetration of the photons appears in Table 3. Tables 2 and 3 demonstrate the relationship that photons of higher energy penetrate deeper into tissue. Since the different Mössbauer isotopes demonstrate a wide range of photon energies, therapies can be designed to exploit this phenomenon to deliver the energy of the radiation to a selected depth. For example, the 14.4 keV gamma ray of ⁵⁷Fe with a mass energy tissue absorption coefficient of 1.32 cm²/g would be suitable for intraoperative radiation of breast, bowel, and pancreatic cancer, whereas the 80.65 keV gamma ray of ¹⁶²Dy with a mass energy bone absorption coefficient of 0.05 cm²/g represents a suitable isotope for the treatment of primary and metastatic bone cancer. Alternative combinations of therapeutic treatments The two major cancer therapies are radiation therapy and chemotherapy. The latter includes agents which can be broken down into six major classes of antitumor agents, alkylating agents, antimetabolites, plant alkaloids, endocrine agents, and immunological stimulants. Radiation and chemotherapy can be combined synergistically by synthesizing hybrid pharmaceuticals consisting of the active functional groups of chemotherapeutic agents and one or more Mössbauer nuclei per molecule. ¹⁹⁵Pt, cisplatinum, is an example of such a hybrid molecule. Cisplatinum is an alkylating chemotherapeutic agent which becomes covalently bound to DNA. Irradiation at a distinct resonance frequency of Mössbauer nucleus, ¹⁹⁵Pt localized in the tumor cells combines the effects of MIRAGE therapy with that of chemotherapy to synergistically enhance tumor cell death. As an alternative to selective kill of target cells due to irradiation at a frequency which is resonant only for the isotope localized to the target cell, MIRAGE therapy could also be made selective by means of developing molecules or ions which are more avidly taken up by the target cells. This constraint is minimized by the relative nontoxicity of any pharmaceutical distributed in nonirradiated areas. Also, the target tissue is irradiated locally; therefore, the enhanced differential uptake would only be relative to other cell populations in the radiation field. The therapy according to the present invention is useful to treat diseases other than cancer. The basis of therapy rests on the selective destruction of one or more cell lines. Other diseases which can be cured by elimination of specific cell lines include autoimmune diseases and transplant rejection disease, graft versus host, and host versus graft. The cellular mediators for both of these diseases are lymphocytes. The responsible cell lines could be selectively killed by synthesizing hybrid pharmaceuticals consisting of a protein and one or more Mößbauer isotopes. The protein binds to the surface of the target cell in a highly specific manner. A monoclonal antibody to an antigen on the cell surface or a hormone which binds to a receptor on the cell surface could serve as the protein. The tissue is irradiated at the Doppler frequency which is the resonant frequency of the absorber isotopes of the hybrid pharmaceutical molecules bound to the target cells. The subsequently released Auger electrons would destroy the target cells. Thus, the cell line responsible for disease can be eliminated without internalization of the hybrid molecule which is necessary in the case of conventional hybrid pharmaceuticals which consist of a specific binding protein and a toxin.

Claims: A method for the selective irradiation of biological materials, particularly of tissues, cells and/or cell components, with exception of methods for the therapeutical and surgical treatment of the human or animal body and diagnostic methods practised on the human or animal body, comprising the following steps: (I) Providing a Mößbauer radiation source selectively emitting γ-radiation of at least one frequency, (II) tuning the frequency of the γ-radiation emitted from the Mößbauer radiation source in accordance with the resonance absorption frequency of a Mößbauer absorber, and (III) irradiating the biological material having incorporated therein the Mößbauer absorber, with Mößbauer resonance absorption of the tuned γ-radiation from the Mößbauer radiation source, the Mößbauer absorber having the corresponding Mößbauer resonance absorption frequency at the specific site where it is localized to provide selective damaging or necrosis of the biological material. The method of claim 1, characterized in that in step II, the frequency of the γ-radiation emitted from the Mößbauer radiation source is tuned by means of Doppler shifting and/or frequency filtering. The method according to claim 1 or 2, characterized in that in step III, a biological material is irradiated wherein the Mößbauer absorber has been incorporated through a Mößbauer isotope itself or a compound comprising a Mößbauer isotope. The method according to claim 3, characterized in that in step III, a biological material is irradiated wherein the Mößbauer absorber has been incorporated through a compound comprising a Mößbauer isotope selected from pharmaceuticals or pharmaceutical compositions, particularly pharmaceuticals or pharmaceutical compositions wherein the Mößbauer isotope is bound to a carrier substance having an affinity for the biological material to be irradiated, and hybrid pharmaceuticals consisting of the active functional groups of chemotherapeutic agents and one or more Mößbauer isotopes per molecule, particularly cis-platinum, alkylating agents, antimetabolites, plant alkaloids, endocrine agents and immunological stimulants. The method according to claim 3 or 4, characterized in that in step III, a biological material is irradiated wherein the Mößbauer absorber has been incorporated through a compound comprising a Mößbauer isotope selected from proteins or polypeptides, enzymes, such as peroxidases and catalases, hormones, monoclonal antibodies, toxins, cytochrome c, hemoglobin and myoglobin. The method according to claim 4 or 5, characterized in that in step III, a biological material is irradiated wherein the Mößbauer absorber has been incorporated through an active ingredient, a pharmaceutical or a pharmaceutical composition which has been added to the biological material to be irradiated or administered to an organism, preferably according to the blood flow of the biological material, the amount of the Mößbauer isotope corresponding in the latter case to the blood concentration in the biological material. The method according to one of claims 4 to 6, characterized in that in step III, a biological material is irradiated wherein the Mößbauer absorber has been incorporated through an active ingredient, a pharmaceutical and/or a pharmaceutical composition comprising a Mößbauer isotope, selected according to the effective penetration depth of the corresponding Mößbauer frequency of said isotope at the biological material to be irradiated, according to the affinity of the Mößbauer isotope for the biological material, or according to the differential isotope uptake of the biological material. The method according to one of claims 4 to 7, characterized in that at least one of the following nuclides are used as Mößbauer absorbers: The method according to one of claims 1 to 8, characterized in that at least one of the following nuclides or at least one of the following nuclide combinations, respectively, are used as Mößbauer radiation source: The method according to one of claims 1 to 9, characterized in that Mößbauer absorbers and Mößbauer radiation sources are used which are selected from the following nuclide combinations: The method according to one of claims 1 to 10, further characterized in that the fluorescence radiation emitted by the excited Mößbauer absorber of the irradiated biological material is detected, and the frequency of the emitted radiation is tuned according to the detected fluorescence radiation. The method according to claim 11, characterized in that the fluorescence radiation is detected in a direction different from the axis direction of the incident radiation. The method according to claim 11 or 12, characterized in that the irradiated biological material is imaged according to the detected fluorescence radiation. The method according to one of claims 1 to 13, characterized in that in step III, a biological material is irradiated wherein the Mößbauer absorber is provided at specific sites therein. A combination comprising a Mößbauer absorber adapted to be located at or in the biological material to be irradiated and an apparatus for the selective irradiation of biological materials, for carrying out the method according to claims 1 to 14, including methods for the therapeutical and surgical treatment of the human or animal body and diagnostic methods practised on the human or animal body, the apparatus comprising (A) a Mößbauer radiation source (50) selectively emitting γ-radiation of at least one frequency, and (B) tuning means (54, 56, 60, 62; 80) for tuning the frequency of the γ-radiation emitted from the Mößbauer radiation source (50) in accordance with the resonance absorption frequency of said Mößbauer absorber. The combination according to claim 15, characterized in that the tuning means are a Doppler shifting device (54, 56, 60, 62) and/or frequency filtering means (80), particularly crystal diffraction means (84). The combination according to claim 15 or 16, characterized in that the Mößbauer absorber is a Mößbauer isotope itself or a compound comprising a Mößbauer isotope. The combination according to claim 17, characterized in that the biological material has the Mößbauer absorber incorporated through a compound comprising a Mößbauer isotope, selected from pharmaceuticals or pharmaceutical compositions, particularly pharmaceuticals or pharmaceutical compositions wherein the Mößbauer isotope is bound to a carrier substance having an affinity for the biological material to be irradiated, and hybrid pharmaceuticals consisting of the active functional groups of chemotherapeutic agents and one or more Mößbauer isotopes per molecule, particularly cisplatinum, alkylating agents, antimetabolites, plant alkaloids, endocrine agents and immunological stimulants. The combination according to claim 17, characterized in that the compounds comprising a Mößbauer isotope as Mösbauer absorber are proteins or polypeptides, enzymes, such as peroxidases and catalases, hormones, monoclonal antibodies, toxins, cytochrome c, hemoglobin or myoglobin. The combination according to one of claims 17 to 19, characterized in that the biological material has the Mößbauer absorber incorporated through an active ingredient, a pharmaceutical and/or a pharmaceutical composition selected according to the effective penetration depth of the corresponding Mößbauer frequency of said isotope at the biological material to be irradiated, according to the affinity of the Mößbauer isotope for the biological material, or according to the differential isotope uptake of the biological material. The combination according to one of claims 15 to 20, characterized by at least one of the following nuclides as Mößbauer absorbers: The combination according to one of claims 15 to 21, characterized by at least one of the following nuclides or at least one of the following nuclide combinations, respectively, as γ-radiation source (Mößbauer source): The combination according to one of claims 15 to 22, characterized by a Mößbauer absorber and a Mößbauer source selected from the following nuclide combinations: The combination according to one of claims 15 to 23, further characterized by means (92) for detecting the fluorescence radiation emitted by the excited Mößbauer absorber of the irradiated biological material. The combination according to claim 24, characterized in that the means (92) detect the fluorescence radiation in a direction different from the axis direction of the incident radiation. The combination according to claim 24 or 25, characterized by means for imaging the irradiated biological material according to the detected fluorescence radiation. Use of the combination according to one of claims 15 to 26 for irradiating biological materials and particularly tissues, cells and/or cell components by selective irradiation with γ-radiation with Mößbauer absorption under such conditions that selective damaging or necrosis of the irradiated material is obtained, with exception of the therapeutical and surgical treatment of the human or animal body and diagnostic methods practised on the human or animal body. Use of the combination according to one of claims 15 to 26 in accordance with claim 27 for irradiating human and animal tissues. Use of the combination according to one of claims 15 to 26 in accordance with claim 27 or 28 for differentiating between diseased or neoplastic and normal cells or tissues.

Inventors: MILLS RANDELL L, MILLS, RANDELL L.
Applicants: MILLS RANDELL L, MILLS, RANDELL L.
Application year: 1986
Main classification: A61N5
IPC codes: A61N5, A61K51, A61K41