Advances in drug delivery systems, challenges and future directions

Abstract

Advances in molecular pharmacology and an improved understanding of the mechanism of most diseases have created the need to specifically target the cells involved in the initiation and progression of diseases. This is especially true for most life-threatening diseases requiring therapeutic agents which have numerous side effects, thus requiring accurate tissue targeting to minimize systemic exposure. Recent drug delivery systems (DDS) are formulated using advanced technology to accelerate systemic drug delivery to the specific target site, maximizing therapeutic efficacy and minimizing off-target accumulation in the body. As a result, they play an important role in disease management and treatment. Recent DDS offer greater advantages when compared to conventional drug delivery systems due to their enhanced performance, automation, precision, and efficacy. They are made of nanomaterials or miniaturized devices with multifunctional components that are biocompatible, biodegradable, and have high viscoelasticity with an extended circulating half-life. This review, therefore, provides a comprehensive insight into the history and technological advancement of drug delivery systems. It updates the most recent drug delivery systems, their therapeutic applications, challenges associated with their use, and future directions for improved performance and use.

Keywords: Chemotherapy; Drug delivery system; Nanocarriers; Nanoparticles; Nanosheet; Pharmacokinetics; Tumour.

Fig. 1

Several types of recent drug delivery systems for different therapeutic purposes.

Fig. 2

Synthetic strategies for RBCM-NPs preparation for antitumor activity. Whole fresh blood is centrifuged and washed multiple times to remove the plasma and other unwanted cells. The resulting pure red blood cells are subjected to hypotonic hemolysis and are used to coat selected nanoparticles which are intravenously injected into the blood to maintain long systemic circulation. The RBCM-NPs permeate the tumor tissue via the EPR effect and finally enter into the tumor cells by endocytosis for therapeutic effect. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

The application of hyaluronic acid-based nanocarriers in cancer treatment. (a) and (b) Direct conjugation of cytotoxic drug with HA or hydrophobic moiety results in self-assembly of nanoparticles (NPs) that can be administered intravenously for cancer cell targeting; (b) HA hydrogel formation using a cationic polymer; (c) Surface coating of NP with HA; (e) Hyaluronic acid-based drug nanocarriers permeate cancerous tissues via EPR effect and binds to the CD44 receptor site to elicit anticancer activity.

Fig. 4

Schematic explanation of H-BN nanosheet drug delivery system. H-BN was exfoliated via chemical treatment and functionalized with Au particles resulting in high loading capacity of DOX, a chemotherapy drug which is released in tumor cells by decrease in pH.

Fig. 5

The formation of a Polymeric-Lipid Hybrid Nanoparticle. The Hybrid contains three distinct components which include: A polymeric core that encapsulates both hydrophilic and hydrophobic drugs effectively. A lipid shell that provides biocompatibility and high stability and a lipid-polyethylene glycol (PEG) that is found in the outer part and covered by a lipid layer to provide increased steric stability, prevent immune recognition and increase time for circulation.

Fig. 6

Mechanism of Self-emulsification in aqueous environment. SEDDS comprise a mixture drugs, surfactants, oil, stabilizers, and cosolvents. Like conventional emulsification, SEDDS (ionotropic mixture) form (o/w) nano or microemulsion within the gastrointestinal tract with very small energy input.

Fig. 7

Schematic representation of MEMS components. Generally, MEMS is made up of mechanical microstructures, microactuators, microsensors, and microelectronics all integrated onto a single silicon chip. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)