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Polymeric materials have already revolutionized the world of biomaterials. Due to their advantageous properties, a considerable amount of work has been done to integrate polymeric nanoparticles with smart drug delivery systems.
An Overview of Polymers in Drug Delivery
Polymeric materials are associated with several properties that make them ideal candidates for biological purposes, particularly in drug delivery systems. Some of the favorable properties of these materials include excellent biocompatibility and biomemetric behavior, in addition to being relatively easy to design and prepare. When incorporated into drug delivery systems, polymers have demonstrated their unique ability to deliver therapeutic agents to specified target tissues effectively.
Polymer Nanocarriers
Some of the most recent work involving polymer nanoparticles for drug delivery purposes has focused on the use of these materials as drug carriers. When used as nanocarriers, polymeric materials of natural, semi-synthetic and synthetic nature are otherwise referred to as spheres and/or capsules. Like any smart drug delivery system, polymer nanocarriers have been shown to provide site-specific targeting of hydrophobic drugs while simultaneously enhancing their bioavailability and controlled release.
Cancer treatment
The most widely recommended therapies offered to cancer patients typically involve chemotherapy, radiation and/or surgery. However, these options are associated with several limitations. For example, chemotherapeutic agents, while highly effective in their ability to kill rapidly dividing cancer cells, are associated with severe cytotoxic effects to normal cells.
Due to these challenges, nanotechnology-based targeted drug delivery systems have been widely investigated for their potential to not only reduce the adverse effects associated with traditional antineoplastic drugs, but also provide enhanced therapeutic efficacy.
Among the various nanotechnology-based systems that have been investigated, polymeric nanocarriers have attracted a considerable amount of attention. Scientists have successfully manipulated the core-shell structure of polymeric nanocarriers to both encapsulate and conjugate drugs to this core.
As well as providing a protective barrier between healthy tissues and the encapsulated drug, polymeric nanocarriers have improved drug pharmacokinetics and enhanced the accumulation of encapsulated drugs directly into tumors.
CNS Disorders
Formed by tight junctions that are joined with the endothelial cells of the central nervous system (CNS), the blood-brain barrier (BBB) is a physical barrier that controls and limits the passage of substances into the brain. While the BBB serves to protect the brain against invading pathogens and potential neurotoxins, it also significantly limits the passage of therapeutic agents into the brain to treat CNS conditions.
Several different types of nanoparticle carriers have been investigated to overcome these challenges, some of which include metallic, polymeric, lipid and targeted nanoparticle carriers.
In comparison to metallic nanoparticles, polymeric nanoparticles are soft, more flexible and less dense, allowing for these particles to be more malleable for therapeutic drug encapsulation.
Various properties of polymeric nanoparticles, such as their size, surface charge and aspect ratio, can be altered to meet the demands of a wide range of drugs. To cross the BBB, polymeric nanoparticles undergo a process called endocytosis, which involves the engulfment of the nanoparticles by the accepting cell’s membrane.
Several studies have also investigated different methods, such as the addition of endogenous substances to functionalize the polymeric nanocarrier’s surface to further enhance the site-specific delivery of encapsulated drugs into the brain.
Oral drug delivery
One of the most convenient methods for drug administration is oral delivery. Not only is this method painless for the patient, but it is a cost-effective solution that has limited sterility constraints and can, therefore, be easily produced.
Unfortunately, oral drug delivery can often result in poor bioavailability of the drug as a result of its aqueous solubility, membrane permeability and stability when present in enzymatic environments, such as that which is present within the stomach. These limitations, therefore, limit the type of drugs that can be given orally, which subsequently leads to poor patient compliance when these drugs must be administered through other methods, such as intravenous or intraperitoneal injection.
Several different polymeric nanoparticle technologies have been developed to facilitate the oral delivery of various drugs, some of which include chemotherapeutic agents, single-strand RNA (siRNA) and small molecule drugs for the treatment of inflammatory bowel disease, as well as insulin for diabetes patients.
While these studies remain in the preclinical stages of their development, they have already demonstrated their tremendous potential for clinical relevance.
References and Further Reading
Bennet, D., & Jim, S. (2014). Polymer Nanoparticles for Smart Drug Delivery. In: Demir Sezer, A. Application of Nanotechnology in Drug Delivery. DOI: 10.5772/58422.
Alsehli, M. (2020). Polymeric nanocarriers as stimuli-responsive systems for targeted tumor (Cancer) therapy: Recent advances in drug delivery. Saudi Pharmaceutical Journal 28(3); 255-265. DOI: 10/1016/j.jsps.2020.01.004.
Hersh, D. S., Wadajkar, A. S., Roberts, N., Perez, J. G., Connolly, N. P., et al. (2016). Evolving Drug Delivery Strategies to Overcome the Blood Brain Barrier. Current Pharmaceutical Design 22(9); 1177-1193. PMID: 26685681.
Gupta, U., & Perumal, O. Chapter 15 – Dendrimers and Its Biomedical Applications. In: Kumbar, S. G., ed. Natural and Synthetic Biomedical Polymers: 2014;243-257. DOI: 10.1016/B978-0-12-396983-5.00016-8.
Pridgen, E. M., Alexis, F., & Farokhzad, O. C. (2014). Polymeric Nanoparticle Technologies for Oral Drug Delivery. Clinical Gastroenterology and Hepatology 12(10); 1605-1610. DOI: 10/1016/j.cgh.2014.06.018.
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