Drug delivery systems

Many drug delivery systems have been explored to overcome drug toxicity limitations while ensuring that adequate bioavailability(1) is consistent. One such system is a drug-encapsulating system, but it has limitations with regard to the size and nature of drugs that can be distributed and released in an effective manner. In addition, drug release depends on capsule degradation, which can lead to a sudden release of drugs instead of a steady and constant drug release.

Hydrogel is one of the latest advances in drug delivery systems. This porous polymer seems to fulfil many of the complicated drug delivery requirements of today’s medicine, especially chemotherapy.

Hydrogels

Hydrogels can swell appreciably in water, and the trapped water within their network structure increases their capacity by over 20%[2]. However, these porous polymers are insoluble in water under physiological conditions. Both synthetic and natural biocompatible materials can be used to prepare hydrogels, this choice allows hydrogels to be prepared with particular physicochemical properties, for example biodegradability[2,3].

A drug is attached to the hydrogel using linkers, which can be chosen based on the desired drug release profile. Different drugs in a chemotherapy cocktail can be released at different rates[2] by attaching them to a hydrogel using different linkers that are individually tuned for each drug. In addition, the composition of hydrogels can be customized so that they are sensitive to various environmental conditions, such as pH, temperature, and enzymatic activities[4].

Thanks to the larger pore size of hydrogels, the transported drug is readily diffused out over a few hours to a few days, based on the composition of gel. During drug release, the hydrogel remains unaffected, eliminating a sudden release of the drug, and ensuring it degrades only after completing its task[2]. Therefore, hydrogels are increasingly becoming a useful tool in chemotherapy[5].

Hydrogel preparation

Many different preparation methods are available for hydrogels, with each developed for a specific application. Since the production conditions and composition of hydrogels determine their properties, their preparation must be rigorously controlled in order to satisfy their specific purpose.

During the synthesis of drug delivery hydrogels, precision is very important because the precise cross-linking structure and composition of these hydrogels can directly affect the efficacy of the drug and the safety of patients.

Hydrogel production involves a series of mixing and heating steps and uses varying temperatures and a range of polymeric supports. As a result, it can be a challenging task to ascertain that all variables are precisely as needed to reproduce hydrogels with the desired structure and composition.

An instrument developed by Vitl Life Science Solutions ensures the reliable reproduction of a particular hydrogel. Featuring mixing tubes and a heated block, Ther-Mix™ avoids the use of shakers, mixers, stopwatches, and incubators, and also eliminates the uncertainty about obtaining the preferred hydrogel.

Ther-Mix™ can store up to 100 mixing programs, each including various heating and mixing steps. Once the Ther-Mix™ is programmed, it produces the desired hydrogel simply at the click of a button.

In his work, Dr Gubala, lecturer in Chemistry and Drug Delivery at the Medway School of Pharmacy, explores hydrogels using Ther-Mix™. And says,

“The Ther-Mix™ allows us to mix the reagents in various ratios, thus creating hydrogels with different properties. We can study up to 24 hydrogels at the same time, whilst ensuring that other variables such as shaking speed and temperature are precisely controlled by the Ther-Mix™.”

Conclusion

For many years, it has been a challenge to biomedical science to deliver the right quantity of drugs to the target site, without causing any toxic effect to the remaining parts of the body. Although a number of methods have been explored in this regard, each comes with its own limitations.

Hydrogels may have resolved most of the challenges to optimal delivery of drugs, proving invaluable especially in the delivery of highly toxic chemotherapy agents. Modifying the composition of a hydrogel can control its properties, thus allowing the location, duration, and timing of drug release to be tailored to fulfil a specific need.

After the development of a specific hydrogel to satisfy a particular drug delivery requirement, the ability to reproduce the hydrogel precisely is equally important. A specific hydrogel can be accurately reproduced using the Ther-Mix™. It is possible to program the Ther-Mix™ to carry out a range of mixing and heating steps.

References

• Tiwari G, Tiwari R, Sriwastawa B et al. Drug delivery systems: An updated review. Int J Pharm Investig. 2012;2(1):2–11.

• Ashley GW, Henise J, Reid R, et al. Hydrogel drug delivery system with predictable and tunable drug release and degradation rates. Proc Natl Acad Sci USA 2013;110(6):2318–2323.

• McKenzie M, Betts D, Suh A, et al. Hydrogel-Based Drug Delivery Systems for Poorly Water-Soluble Drugs. Molecules 2015, 20, 20397–20408.

• Singh, N.K.; Lee, D.S. In situ gelling pH- and temperature-sensitive biodegradable block copolymer hydrogels for drug delivery. J. Control Release 2014, 193, 214–227.

• Cassano R, Mellace S, Pellegrino M, et al. Biocompatible Targeting Hydrogels For Breast Cancer Treatment. Mini Rev Med Chem. 2016;16(8):651 657.

• http://www.vitlproducts.com/