Apparatus and method for delivery of surgical and therapeutic agents

Localized, transient pressure waves are applied to tissue adjacent to target cells by means of a light source and a coupling interface placed in contact with the tissue that converts light from the light source into acoustic energy. The pressure waves cause transient poration of the cell membranes. The therapeutic agents are delivered to the site of the localized pressure waves by any suitable means, such as by injection with a needle. The light source and coupling interface can be incorporated into a catheter for application of the pressure waves to diseased blood vessels. A manually manipulable surgical device incorporating a needle for injecting the agent, light source, and coupling interface is also described.

BACKGROUND OF THE INVENTION 
A. Field of the Invention 
The present invention relates to the treatment of disease or ailments in 
humans or animals. More particularly, the invention relates to a method 
and apparatus to deliver surgical or therapeutic compounds such as drugs 
and genes into cells of human or animal tissues. 
B. Description of Related Art 
Gene therapy represents a promising modality for the treatment of a variety 
of acquired and inherited diseases afflicting humans of all ages. The 
therapy involves the introduction of genes into cells so as to correct for 
defective genes responsible for the cause of the ailment or disease. There 
are two approaches to performing gene therapy; ex-vivo and in-vivo. 
Ex-vivo requires the harvesting of cells, introduction of genes into 
harvested cells, and subsequent implantation of cells back into the human 
or animal body. In-vivo gene therapy negates the need to harvest cells 
since direct injection of genes into tissues is more convenient as a 
treatment modality. In-vivo gene therapy is desirable since it resembles 
conventional drug therapy. 
There are several methods of gene delivery required in conjunction with 
in-vivo gene therapy. These methods serve to introduce the desired genes 
into patient cells. The most promising for high efficiency of gene 
expression is the use of a viral vector. A viral vector contains the 
therapeutic gene attached to a key promoter of an attenuated virus. Once 
introduced into tissue, a viral particle infects a cell lacking the 
desired gene and subsequently incorporates the therapeutic gene within the 
genetic system of the cell. But the use of a viral vector introduces 
issues of toxicity and safety since viral vectors can produce protein 
products that are allergenic to the patient as well as the possibility of 
causing uncontrolled growth by random translocation. Therefore the use of 
non-viral gene delivery methods are more desirable for the future. 
Recently it was discovered that direct injection of plasmid DNA into 
skeletal muscle can be taken up by muscle cells and be expressed in animal 
cells. Direct injection of genetic material into tissues should alleviate 
the issues of toxicity and safety in humans but the efficiency of 
expression of the plasmid DNA is rather low. This is attributable to the 
low amount of plasmid DNA that actually get transported through cell 
membranes and subsequently make their way to the nuclei of cells. Thus, 
there exists the need to enhance transport of genetic materials into 
intracellular space as well as transport to the vicinity of the nucleus. 
Several chemical and physical methods have been applied with direct 
injection of genes to enhance the efficiency of gene uptake and subsequent 
expression. The chemical methods range from combining the naked DNA with 
calcium phosphate precipitate to the use of liposomes and 
receptor-mediated molecules. The physical methods range from 
electroporation to biolistic transport. 
Electroporation uses brief electrical pulses produced by electrodes in the 
range of kV/cm to create transient pores in cell membranes located between 
the electrodes. Biolistic transport is the bombardment of cells or tissues 
with particles coated with DNA. The particles are accelerated into tissue 
by devices analogous to guns. The guns generate explosive acceleration by 
either using very high pressure gases or by electric field discharge. 
These physical gene delivery methods have demonstrated practical utility 
for in-vitro transfection of animal and plant cells and limited in-vivo 
transfection of animal and human tissues. 
Although electroporation and biolistics have demonstrated practical gene 
delivery into tissues, their use on human tissues are limiting by the 
nature of their means of implementation. Electroporation uses very high 
voltage potentials and requires that the cells be placed in between the 
electrodes. Gene delivery into confined spaces such as the inner walls of 
blood vessels and arteries is problematic due to limited working spaces 
and relatively delicate nature of the tissues. High voltages placed on the 
surface of tissues such as skin will produce damage due to excessive 
heating and dielectric breakdown. Particle acceleration into tissues is 
limiting by the use of guns requiring high gas pressure and electric 
discharge to accelerate them. These requirements tend to produce devices, 
although hand-held, that are relatively large and limit their application 
to superficial distances from the tissues as well as in confined spaces 
such as blood vessels or in various cavities of the body such as the 
lungs. Thus there exists a need for method and device that can effect 
membrane permeability with relatively less traumatic means as well as 
providing easy access to confined, or spaces deep within animal and human 
organs. Ultimately the method and apparatus serve to enhance the uptake 
and subsequent expression of direct injection gene therapy. 
Patents of interest related to the present invention include the patents 
issued to Sandford et al., U.S. Pat. Nos. 5,487,744, 5,371,015, 5,100,792 
and 5,036,006; the patents to Shimada et al., U.S. Pat. No. 4,819,751; 
Shimada et al., U.S. Pat. No. 5,267,985; Lipkover, U.S. Pat. No. 
5,421,816; Shapland et al., U.S. Pat. No. 5,286254; Shaplan et al., U.S. 
Pat. No. 5,498,238; Eppstein et al., U.S. Pat. No. 5,445,611; the patents 
to Hoffinann et al., U.S. Pat. Nos. 5,439,330 and 5,507,724; Crandell et 
al., U.S. Pat. No. 5,304,120 and Miller, Jr., U.S. Pat. No. 5,141,131. 
SUMMARY OF THE INVENTION 
A device and methods are provided for using stress and thermal confinement 
of light energy to enhance membrane permeability and subsequent transport 
of surgical and therapeutic agents such as naked DNA or drugs into the 
intracellular spaces of plant structures, animal, and human tissues. 
In one aspect of the invention, a device is provided for delivering 
therapeutic agents into cells of body. The device is for use in 
conjunction with a source of therapeutic agents delivered to tissue in the 
vicinity of the cells. The device comprises a light source, such as laser, 
emitting radiation and a coupling interface receiving the radiation from 
the light source. The radiation and coupling interface are positioned 
adjacent to the body such that the coupling interface is in contact with 
the tissue. The light source and coupling interface cooperate to 
responsively generate a localized, transient pressure wave in the tissue 
of the body so as to cause transient poration of the membrane of said 
cells, whereby the transient poration of the membrane permits the 
therapeutic agents to be assimilated into the cells. 
An object of this invention is to provide an apparatus and method of 
producing mechanical wave gradients, in-vivo, to create transient poration 
of cell membranes, and to transport surgical and therapeutic agents into 
the vicinity of the cell nucleus. 
One embodiment of this invention provides an apparatus for the introduction 
of surgical and therapeutic agents into the cells of the organ of skin. 
Another embodiment of this invention provides a surgical needle capable of 
delivering the surgical agents, therapeutic agents, absorbing dyes, and 
particulates, and the stress waves into the vicinity of direct injection. 
Yet another embodiment of the invention provides for the creation of shock 
waves within a liquid reservoir or tissues to accelerate particulates 
having the surgical or therapeutic agents attached to the particulates 
into intracellular space of animal and human tissues. 
Yet another embodiment of the invention is a catheter having reservoirs for 
the surgical, therapeutic agents, dyes, and particulates in combination 
with means for producing shock waves to accelerate particulates into 
peripheral tissues of blood vessels and tissues of human organs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a first embodiment of the apparatus includes a drug 
delivery device 1 containing a laser light source and electronics 2 to 
control the operation of the light source. Element 2 is capable of 
providing a light beam 4 of a specific duration and amount of specific 
energy level. The characteristics of the light beam are determined by a 
beam conditioner 3. The beam conditioner 3 contains elements that 
determine the beam diameter, the distance of the focal spot, and the 
intensity distribution of the beam across its diameter. 
The light beam 4 is directed through a coupling interface 5. The coupling 
interface 5 facilitates the transfer of light energy into mechanical 
pressure waves. The coupling interface can be a rigid material having 
optical absorption properties sufficient to produce stress waves (i.e., 
mechanical pressure or acoustic waves) when a brief pulse of light is 
applied within the material. The coupling interface 5 can be a reservoir 
containing various solutions having different optical absorption 
properties. The light beam 4 is applied within human tissue 7 to produce a 
propagating mechanical pressure wave gradient 6. The mechanical wave 
gradient provides a means of creating transient poration of cell membranes 
within the tissue. 
The drug delivery device 1 is used in combination with direct injection and 
parenteral administration of surgical and therapeutic agents for isolation 
and local delivery of the agents 9 into cells 8. The process proceeds as 
follows: after introduction of the surgical and therapeutic agents into a 
local tissue region, the light beam 4 of the device 1 is applied in the 
vicinity of the location of administration. The light beam 4 and coupling 
interface 5 produces mechanical wave pressure gradients that effect cell 
permeability by transferring radial, circumferential, longitudinal and 
shear stress so as to deform the cells 8. Cell volume deformation produces 
transient stresses on cell membranes due to a differential change in 
surface area. 
The pressure gradients affecting cell membranes are produced in a 
controlled manner by manipulating the characteristic of the light energy 
deposition process into the coupling interface 5 and/or tissue. The 
conversion of light energy into mechanical waves is governed by the 
process of thermal elastic expansion in the coupling interface material 5. 
When light energy is applied in a brief manner to a material or medium, 
heat is generated which is converted into acoustic waves as the energy is 
dissipated to the surrounding medium. Stress generation is governed by the 
thermal diffusion and the speed of sound of a material or medium. 
Depending on the time duration of a pulse of light, high stress or 
pressure can be generated in a medium. For effective delivery, light of 
sufficient energy is applied so as to not create pressure waves sufficient 
to permanently damage or lyse the cells. 
Stress generation by confinement is the preferred method of production due 
to its relatively small increase in temperature. The laser pulse heats the 
coupling interface medium much faster than the time required for the 
stress waves to propagate through the irradiated volume. A dimensionless 
parameter of stress confinement is the product of the optical absorption 
coefficient, the speed of sound, and the laser pulse duration. This 
parameter can be used to determine the degree of confinement. The energy 
per area of a light pulse and its repetition rate can be used to create a 
stress gradient within a specific region of tissue as the mechanical waves 
travel from the irradiated spot. The boundary of the irradiated medium 
also determines reflected waves that can provide tensile stresses to 
tissues within a location. 
In addition to the creation of the transient poration of cell membranes, 
the propagating acoustic waves, which have very high frequencies, create 
microstreaming motions within regions containing liquid such as 
extracellular space of tissue and intracellular space of cells. Since 
microstreaming is proportional to acoustic absorption, the high 
frequencies can promote effective microstreaming forces due to rapid 
attenuation of the propagating wave. The microstreaming forces can result 
in circular motion of the extracellular liquid and the cell cytoplasm. 
This motive action can enhance transport of the delivered agents into the 
intracellular space as well as toward the nucleus of the cell. 
Microstreaming increases the probability of the agents to be transported 
into nucleus of the cell. 
One mode of practice of confined stress generation of acoustic waves is the 
use of a Nd:YAG laser operating in a Q-switched mode (Model YG 681, 
Quantel International, Santa Clara, Calif.). The device is used to create 
stress waves in skin tissue to deliver genes or therapeutic agents into 
skin cells to cure a variety of skin diseases such as cancer and psoriasis 
after direct injection or topical application of the agents. Short laser 
pulses, with duration of nanoseconds to microseconds, can be applied to a 
localized area within tissue. In some applications, the coupling interface 
can be used to generate the stress gradient within the coupling interface. 
The stress gradient then propagates into the underlying tissues. The 
coupling medium serves to enhance coupling of the acoustic waves into the 
underlying tissues. The coupling medium 5 can be a solid-like glass doped 
with absorption centers or a liquid such as a buffer. The buffer can also 
contain non-irritating dyes that serve as the absorption medium and the 
surgical or therapeutic agents needing delivery. 
Referring to FIG. 2, a second embodiment of the invention includes a light 
source 2 that produces a pulse of light beams 16 modified by a focusing 
element 12 through a reservoir barrel 13 resembling a syringe and a needle 
15 to produce pressure waves in the vicinity of injection inside tissue 7. 
The light beam 16 traverses a solution 14 containing the surgical or 
therapeutic agent 9 and/or absorption enhancement dye or particulates 
coated with the therapeutic agents. 
The method of application of the second embodiment, described above, 
preferably is accompanied by the simultaneous injection of the therapeutic 
agents into tissue and delivery of short pulses of light into the tissue 
space. As the agents 9 are injected into tissue the generation of pressure 
waves 6 create stresses as to permeate the cell membranes of the 
surrounding tissue. A non-irritating, non-toxic dye having the appropriate 
absorption can also be mixed with the agents as to enhance the conversion 
of light energy into mechanical waves. 
Another method of application is to inject coated and non-coated 
particulates heterogeneous in size having a defined absorption coefficient 
such as carbon particles into the tissue using the needle device. A shock 
wave is generated using the light source with sufficient energy density 
and temporal duration to accelerate agent-coated particulates into the 
surrounding cells. The non-coated particles having larger sizes are used 
to facilitate the creation of shock waves due to rapid thermal expansion 
created by absorption of light energy from the laser beam. The 
particle-liquid-air interface will provide a means of generating tensile 
stress within the particles as to generate shock waves. The shock wave 
produces an explosion that accelerates small agent coated particles into 
the cells as it propagates outward to the surrounding tissues. 
To facilitate the optical set-up for light delivery, the needle device 
13/15 can be modified by placing the plunger or piston used to push fluid 
such that its axis is either perpendicular to the axis of the light beam 
or at some other appropriate angle. The light beam 16 can also be 
delivered with a fiber optic filament that is axially aligned with the 
needle axis. The fiber can have focusing elements at its tip or it can 
have a flat profile of light intensity. This embodiment would enable easy 
transfer of direct injection of agents in combination with mechanical wave 
generation at joint spaces such as knee joints or deep within the body. 
Referring to FIG. 3A, another embodiment is illustrated wherein the gene or 
therapeutic agent is delivered with a catheter 23 containing a fluid 
conduit 27 and an optical fiber 24 to a site within a blood vessel 30. The 
tip of the catheter 23 contains a cap 29 having a reflective surface 35 
and a cavity 36. The reflective surface 35 directs the light pulse exiting 
the fiber into the direction perpendicular to the axis of the catheter. 
The cavity 36 provides fluid access to the adjacent diseased vessel 
tissues 32. The fluid conduit 27 contains an entering path and an exit 
path forming a loop within the cavity 36. The fluid conduit provides fluid 
circulation and the delivery of a bolus containing the therapeutic agents 
is synchronized with the application of the light pulse during agent 
delivery into the cells of the vessel tissues 32. 
FIG. 3B is a variation of the catheter for delivery of genes of therapeutic 
agents within a diseased blood vessel. The catheter contains an optical 
fiber 42 that conducts light energy to an optically absorbent element or 
coupling interface 44. The optical absorbing element 44 is contained in a 
tip 43 which also has a cylindrical cavity 45. Cavity 45 is connected to a 
conduit 41 that provides fluid entrance and exit. The conduit can 
transport fluid containing agent-coated particulates such as gold or 
tungsten. 
A shock wave is generated using the light energy delivered to the absorbing 
element 44. Ablation of a small amount of the absorbing element 44 may 
occur, which facilitates the creation of a tensile stress which adds to 
the compression stress. The spallation of the ejected mass creates a shock 
wave that propagates in a radial direction. The shock wave accelerates the 
particulates that are synchronously delivered to the cavity 43. The 
accelerated particles travel radially into the surrounding tissues of the 
blood vessel. The particles penetrate through the cell membranes without 
lysis. Another means is to coat the inner wall of the cylindrical cavity 
45 coated particulates. The shock wave is produced within element 44 that 
subsequently transfers its energy to accelerate the particles off the wall 
and into the cells of the tissues of the periphery of the blood vessel. 
To provide ease of use of the above described embodiments, an agent 
delivery device comprising light source, coupling interface and 
therapeutic agent source may be manufactured as a unitary implement 
incorporating a compact handle. The device can also be incorporated into a 
"gun" by the use of compact laser diodes. The principle and device can be 
combined with minimally invasive imaging or scopes to administer gene 
therapy to various cavities within the human body. Although the preferred 
embodiment discloses a specific laser for illustrative purposes, it is 
understood by the person of ordinary skill in the art that wavelengths 
ranging from 190 nm to 3000 nm can be used to generate pressure waves. The 
time duration of picoseconds to seconds can be used. The temperature 
created in tissue can range from 20 degrees Celsius to 100 degrees 
Celsius. Since stress produced is proportional to temperature, it is 
understood that in order to prevent cell lysis, temperature within the 
physiologically tolerable range should be used.