Electrospray and its medical applications

The uniqueness of the electrospray techniques relies on its ability to produce highly charged, monodisperse particles in the diameter range from nanometer to supermicrometer. Due to the electrical charges of the same polarity electrosprayed particles are non-agglomerated. The technology allows users to gain greater control on the generation, dispersion and deposition of particles over other atomization techniques. It allows users to tailor particles to the desired size, morphology and construction for improved particle function and transport properties, making the technique suitable for many particle applications, especially for medical and biological applications. In this chapter we have briefly reviewed the history and the evolution of the electrospray technique. Single- And dual capillary electrospray techniques were introduced. The up-to-date basics on the operation of single- And dual- capillary ES techniques were also summarized. The last part of this chapter has been devoted to provide example applications of the electrospray technique in medical and biological areas. Many studies have been reported on using the electrospray technique for medical applications. More work is needed to take this wonderful technology to the next level for practical applications. One issue is related to the mass throughput of the electrospray technique. Limited success has been reported using the multiple capillary systems. All the reported works with multiple capillary systems involved spraying solutions of low surface tension and electrical conductivity, resulting in less electrical charges on particles and thus lower space effect attributed by the charged particles. The space charge effect resulted from the charged particles in high concentration will eventually limit the number of capillaries that can be deployed in the multiple capillary ES systems. The mass throughput of multiple capillary systems cannot be scaled up indefinitely. A breakthrough design for implementing the multiple capillary systems will be needed in the future. Another concern of using electrospray for medical application is related to the viability of biomaterials after spraying even though the viability of some biomolecules has been established (Kwok et al. 2008; Clarke and Jayasinghe 2008). Potential damage to the bio-molecular structure exists, especially for fragile bio-molecules. To evaluate the bio-viability of sprayed biomaterial is always a necessary step in the technology development. The situation also calls for the development of a soft electrospray technique to ensure no damage to the sprayed bio-materials. Lastly, the control of electrical charges on the electrosprayed particles is often accomplished through the use of corona discharge devices, either DC or AC. It is because of the gradually tightened safety regulation for the use of radioactive materials for neutralizing the charged particles. Unfortunately, ozone is also produced in the corona discharge process. The strong oxidation ability of ozone presents the threat of bio-material damage; it also has adverse health effect on the patient if ES was used to deliver the medicine into the human lung. An alternative approach to controlling the charges on the electrosprayed particles will be much needed for the medical application of the electrospray technique.