Electronic Drug Delivery Systems

INTRODUCTION:

The method by which drug is delivered can have a significant effect on the drugs therapeutic efficacy. Conventional drug delivery systems produce a sharp initial increase in drug concentration to a peak above the therapeutic range followed by fast decrease in concentration to level below the therapeutic range. Additionally, repeatable dosing of medication may be difficult to patient due to their noncompliance. In controlled drug delivery systems (CDS), drug delivery is mainly focused on achieving a constant release of drug over long periods with minimum side effects and the improvements in these delivery systems are elimination of side effects, optimized therapy and better patient compliance. In general, a biodegradable (or) biodiffusible device could provide multi-dose drug delivery advantageous for long-term treatment. In this aspect, microchips were introduced that releases different chemicals for long period at different intervals of time with accurate dosage. These devices would give us much better control of dosing, thus enhancing the effectiveness of the drug while limiting its toxicity. Such chips are called as biological Micro Electrical Devices (bioMEMS). This microchip is a drug delivery device and it can store and release different chemicals on demands from tiny reservoirs by applying a small electrical voltage between a specific reservoir and a gold cap covering it. Thereby, the cap was dissolved and releases chemical inside the body. Eg: Anesthetic to be released slowly would be advantageous. A surgeon could place slow-release anesthetic in the tissue near wound at the end of the surgical procedure for post-operation pain relief, thereby drug is released slowly inside the body to prevent the pain impulses from reaching the brain. So, this CDS have many applications in postoperative surgical procedures.

WORKING OF MICROCHIP:

The prototype device contains 34 reservoirs made of biodegradable polymers that have 1.7 cm width with a height of 0.31 mm and each covered with a thin gold or Titanium film. By using photolithography, chemical vapor deposition (or) microfabrication process, these microchips are fabricated. Each reservoir present in chip is capable of holding about 100-300nl of chemical in solid (or) gel form, but there is space for over 1,000 reservoirs. The reservoirs and microchips could be made much larger (or) smaller on the desired application and these reservoirs were filled via microinjection process. The release mechanism of drug from each reservoir is based on the dissolution of thin anode membrane and it is possible to obtain pulsatile release of different drugs from different reservoirs. This microchip has a battery and a microprocessor into which patient's drug information is stored before implantation. When the device receives a signal from the microprocessor, the battery sends a pulse of one volt between specific reservoir cap made of gold (or) platinum (or) titanium and cathode, so the anode dissolves due to an electrochemical reaction and drug is liberated, but the cathode remains intact during this process. Multiple drug delivery is also possible from the microchip i.e., multiple chemicals in separate reservoirs are liberated at different intervals. In other words, application of small voltage between a reservoir containing chemical A and cathode results in release of chemical A only. This experiment was done for several different reservoirs filled with same (or) different chemicals over a period of several hours. This shows that multiple compounds can be released independently from a single microchip device.

POLYMERS USED FOR THE CONSTRUCTION OF A MICROCHIP:
Polymers used in the construction of microchips are Polymerized type of anhydride crossed with sebacic acid. Rate of release could be changed with the amounts of sebacic acid. Polyurethane and Cellulose Acetate are also used.

ADVANTAGES:
? The controlled-release microchip has a number of advantages over traditional polymeric implants. This polymeric microchip is directly embedded into the body, thereby drug is released directly into the affected area via diffusion (or) surface erosion process.
? The device also has other advantages such as small size and quick response times. These could lead to reduce surgical invasiveness as well as number of surgical sequences.
? These devices are having advantage over traditional drug delivery systems regarding diagnostic purposes.
? The new chip would allow us to control not only the drug release, but also the exact time of delivery.
? These drug delivery devices would give us much better control of dosing thus enhancing effectiveness of the drug while limiting its toxicity.
? These microchips are having ig promise in frightening serious diseases.
? These devices avoid costs as well as risks associated with multiple surgeries.
? Biologically degradable polymers used in manufacturing of microchips are mechanically and physically stable over the period during which the drug is released into the body. After release of drug, polymer would degrade in vivo to smaller fragments that will be excreted from the body.
? Microchips are also equipped with sensors to detect mutated genes or dangerous levels hormones and enable doctors to determine, which tissues to treat.
? Microchips could contain stem cells that would grow and proliferate inside the body. Instead of transplanting whole organ, we would do a transplant using a chip containing stem cells.
? These implantable chips are also used to gather information on matters regarding blood flow characteristics without the need for a physician to examine blood vessels.

CONCLUSION:

The controlled release of therapeutic microchips can have great benefit in treatment of many diseases. The release patterns with one or more therapeutic drugs from this microchip device are complex. The drugs can be released in a controlled manner based on the dissolution of the gold or platinum or titanium membrane. There is a potential to develop chip containing vaccine (or) slow releasing capsule that can target specific type of cancer. The possibility also includes cellular therapy, a device containing a nanoneedle to analyze cells of the heart tissue in patient suffering with heart disease. Using such small needle, would allow doctors to see damaged genes.

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