Polymeric Nanoparticles for Drug Delivery.

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Self-Immolative Polymer Nanoparticles with Precise and Controllable pH-Dependent Degradation.

Polymer nanoparticles have generated significant interest as delivery systems for therapeutic cargo. Self-immolative polymers (SIPs) are an interesting category of materials for delivery applications, as the characteristic property of end-to-end depolymerization allows for the disintegration of the delivery system, facilitating a more effective release of the cargo and clearance from the body after use. In this work, nanoparticles based on a pH-responsive polymer poly(ethylene glycol)-b-(2-diisopropyl)amino ethyl methacrylate) and a self-immolative polymer poly[N,N-(diisopropylamino)ethyl glyoxylamide-r-N,N-(dibutylamino)ethyl glyoxylamide] (P(DPAEGAm-r-DBAEGAm)) were developed. Four particles were synthesized based on P(DPAEGAm-r-DBAEGAm) polymers with varied diisopropylamino to dibutylamino ratios of 4:1, 2:1, 2:3, and 0:1, termed 4:1, 2:1, 2:3, and 0:1 PGAm particles. The pH of particle disassembly was tuned from pH 7.0 to pH 5.0 by adjusting the ratio of diisopropylamino to dibutylamino substituents on the pendant tertiary amine. The P(DPAEGAm-r-DBAEGAm) polymers were observed to depolymerize (60-80%) below the particle disassembly pH after ∼2 h, compared to <10% at pH 7.4 and maintained reasonable stability at pH 7.4 (20-50% depolymerization) after 1 week. While all particles exhibited the ability to load a peptide cargo, only the 4:1 PGAm particles had higher endosomal escape efficiency (∼4%) compared to the 2:3 or 0:1 PGAm particles (<1%). The 4:1 PGAm particle is a promising candidate for further optimization as an intracellular drug delivery system with rapid and precisely controlled degradation.

Quantifying the Endosomal Escape of pH-Responsive Nanoparticles Using the Split Luciferase Endosomal Escape Quantification Assay.

All nanoparticles have the potential to revolutionize the delivery of therapeutic cargo such as peptides, proteins, and RNA. However, effective cytosolic delivery of cargo from nanoparticles represents a significant challenge in the design of more efficient drug delivery vehicles. Recently, research has centered on designing nanoparticles with the capacity to escape endosomes by responding to biological stimuli such as changes in pH, which occur when nanoparticles are internalized into the endo-/lysosomal pathway. Current endosomal escape assays rely on indirect measurements and yield little quantitative information, which hinders the design of more efficient drug delivery vehicles. Therefore, we adapted the highly sensitive split luciferase endosomal escape quantification (SLEEQ) assay to better understand nanoparticle-induced endosomal escape. We applied SLEEQ to evaluate the endosomal escape behavior of two pH-responsive nanoparticles: the first with a poly(2-diisopropylamino ethyl methacrylate) (PDPAEMA) core and the second with 1:1 ratio of poly(2-diethylamino ethyl methacrylate) (PDEAEMA) and PDPAEMA. SLEEQ directly measured the cytosolic delivery and showed that engineering the nanoparticle disassembly pH could improve the endosomal escape efficiency by fivefold. SLEEQ is a versatile assay that can be used for a wide range of nanomaterials and will improve the development of drug delivery vehicles in the future.