# An Overview on Atomization and Its Drug Delivery and Biomedical Applications
## 6 Drug Delivery Applications  
There are many means to supply drugs into the human body. The conventional and the most expedient method of taking medicines is by ingestion but one limitation is that only chemically defiant materials can be distributed [61]. Inhalation is another way of delivering medicines to the human body. This is the fastest route to supply the drug into different organs through the blood circulation of the body [62]. This route of drug delivery is being widely used for the treatment of many diseases, especially for asthma, diabetes, lung disorders, cancer, etc. The target for this treatment modality is the human lungs as it can easily absorb the drug and transport it into the blood and also the drugs are not digested by the digestive enzymes, as in lungs there are low digestive enzymes [63]. Transcytosis is the mechanism through which the polypeptides and other biomolecular drugs are absorbed into the lung tissue to the blood vessels [64].  
There are different types of inhalers available in the market and the most common type is, in which the medicine is available in the form of a suspension with a liquid propellant. When pressure is applied the suspension of medication is atomized into droplets in the presence of air and releases the medicine into the lungs [62]. Another one is the dry powder inhalers in which aerosols are generated in the presence of air. Table 3 briefly discusses the types of aerosol initiating techniques that are being industrially practiced.  
Depending on the energy source provided in the process and the type of atomizers used there are different types of devices that can be used in drug delivery applications. Another factor that plays a major role in the efficacy of this drug delivery system is the size of the atomized particles generated. It is observed that the atomized droplets that are used in medical applications should have a diameter less than 10 \(\upmu\)m [7]. For pulmonic applications, the size of the drops should be less than 7 \(\upmu\)m as it has to pass through the lung tissue [69]. Drug delivery applications-drop diameter should be 3-5 \(\upmu\)m [70]; drug supply to alveoli sacs-drop diameter should be 1-3 \(\upmu\)m [71].  
Electro hydrodynamic atomization or simply electrospray is the methodology used for a guided and continuous drug delivery by enclosing the drug in a microparticle which is mostly a biodegradable polymers [72]. In the presence of an electric field, the liquid stream is atomized to generate very fine mist [73]. [PERSON] and his group developed a drug loaded micro/nanoparticle by utilizing the coaxial electro hydrodynamic atomization technique. The polymer they used was the poly(lactic-co-glycolic) acid (PLGA). This was developed as a core shell system in which the drug was in the core and the polymer was encapsulating the drug. The size of the particles obtained in the atomized spray were in the range of 165 nm-1.2 \(\upmu\)m with an encapsulation ability of 100% [74]. Later, another investigation was done by the same researchers in which they encapsulated the PLGA coating on multiple drugs by employing the coaxial triple-fluid nozzle system and studied the delivery profile of the drug by comparing it with their previous study [75]. [PERSON] et al. modified the coaxial electro hydrodynamic atomization method by incorporating two drugs, one hydrophobic and another hydrophilic in the core and shell of a microparticle. The core of the microparticle was made up of polylactic acid to which the hydrophobic drug paclitaxel was embodied and the shell was made up of PLGA polymer to which the hydrophilic drug suramin was added. They found that the release of the drugs in the above-mentioned system is subsequent, and it lasted for a period of 30 days. When the hydrophilic drug was entrapped in the core and the hydrophobic drug in the shell, they observed an aligned delivery of the drugs from the microparticles [76].