Externally Triggered Drug Delivery Techniques Using Micro and Nanoparticles

The need for sustained and better-controlled drug administration has led to development of novel drug delivery systems. The concentration of a drug in blood at any given time depends on the prescribed routine of drug intake. Conventional methods of drug intake do not always maintain the required consistent drug concentration. Controlled drug release mechanisms can help in maintaining drug dosage levels while optimizing therapeutic effects. Microparticles and nanoparticles, initially developed as carriers for vaccines and anticancer drugs, are being used in drug delivery systems for drug targeting, improved release profile and efficiency. The drugs can be encapsulated inside the particles, suspended in or with them. However, release of the drug depends on the type of techniques used to trigger drug delivery. This review outlines the major techniques used for drug delivery applications based on external triggering mechanisms while utilising micro and/or nanoparticles. These techniques include ultrasound, light, radiofrequency, electric and magnetic field exposures. Most of these techniques have largely remained in vitro owing to challenges concerning safety due to exposure levels and penetration of external signals due to human physiology. Considering these aspects of the challenge, microwave based external triggering can be a prospective technology for drug delivery using micro and nanoparticles.