Mixed polycarbonate prodrug nanoparticles with reduction/pH dual-responsive and charge conversional properties

Synthesis approaches of amphiphilic copolymers for spherical micelle preparation: application in drug delivery

The formation of polymeric micelles in aqueous environments through the self-assembly of amphiphilic polymers can provide a versatile platform to increase the solubility and permeability of hydrophobic drugs and pave the way for their administration. In comparison to various self-assembly-based vehicles, polymeric micelles commonly have a smaller size, spherical morphology, and simpler scale up process. The use of polymer-based micelles for the encapsulation and carrying of therapeutics to the site of action triggered a line of research on the synthesis of various amphiphilic polymers in the past few decades. The extended knowledge on polymers includes biocompatible smart amphiphilic copolymers for the formation of micelles, therapeutics loading and response to external stimuli, micelles with a tunable drug release pattern, etc. Different strategies such as ring-opening polymerization, atom transfer radical polymerization, reversible addition-fragmentation chain-transfer, nitroxide mediated polymerization, and a combination of these methods were employed to synthesize copolymers with diverse compositions and topologies with the proficiency of self-assembly into well-defined micellar structures. The current review provides a summary of the important polymerization techniques and recent achievements in the field of drug delivery using micellar systems. This review proposes new visions for the design and synthesis of innovative potent amphiphilic polymers in order to benefit from their application in drug delivery fields.

Tuning Net Charge in Aliphatic Polycarbonates Alters Solubility and Protein Complexation Behavior

A synthetic strategy yielded polyelectrolytes and polyampholytes with tunable net charge for complexation and protein binding. Organocatalytic ring-opening polymerizations yielded aliphatic polycarbonates that were functionalized with both carboxylate and ammonium side chains in a post-polymerization, radical-mediated thiol-ene reaction. Incorporating net charge into the polymer architecture altered the chain dimensions in phosphate buffered solution in a manner consistent with self-complexation and complexation behavior with model proteins. A net cationic polyampholyte with 5% of carboxylate side chains formed large clusters rather than small complexes with bovine serum albumin, while 50% carboxylate polyampholyte was insoluble. Overall, the aliphatic polycarbonates with varying net charge exhibited different macrophase solution behaviors when mixed with protein, where self-complexation appears to compete with protein binding and larger-scale complexation.

Recent Advancements in Stimuli Responsive Drug Delivery Platforms for Active and Passive Cancer Targeting

The tumor-specific targeting of chemotherapeutic agents for specific necrosis of cancer cells without affecting the normal cells poses a great challenge for researchers and scientists. Though extensive research has been carried out to investigate chemotherapy-based targeted drug delivery, the identification of the most promising strategy capable of bypassing non-specific cytotoxicity is still a major concern. Recent advancements in the arena of onco-targeted therapies have enabled safe and effective tumor-specific localization through stimuli-responsive drug delivery systems. Owing to their promising characteristic features, stimuli-responsive drug delivery platforms have revolutionized the chemotherapy-based treatments with added benefits of enhanced bioavailability and selective cytotoxicity of cancer cells compared to the conventional modalities. The insensitivity of stimuli-responsive drug delivery platforms when exposed to normal cells prevents the release of cytotoxic drugs into the normal cells and therefore alleviates the off-target events associated with chemotherapy. Contrastingly, they showed amplified sensitivity and triggered release of chemotherapeutic payload when internalized into the tumor microenvironment causing maximum cytotoxic responses and the induction of cancer cell necrosis. This review focuses on the physical stimuli-responsive drug delivery systems and chemical stimuli-responsive drug delivery systems for triggered cancer chemotherapy through active and/or passive targeting. Moreover, the review also provided a brief insight into the molecular dynamic simulations associated with stimuli-based tumor targeting.

Enhanced lysosome escape mediated by 1,2-dicarboxylic-cyclohexene anhydride-modified poly-l-lysine dendrimer as a gene delivery system

Antisense oligodeoxynucleotide (ASODN) can directly interfere a series of biological events of the target RNA derived from tumor cells through Watson-Crick base pairing, in turn, plays antitumor therapeutic roles. In the study, a novel HIF-1α ASODN-loaded nanocomposite was formulated to efficiently deliver gene to the target RNA. The physicochemical properties of nanocomposite were characterized using TEM, FTIR, DLS and zeta potentials. The mean diameter of resulting GEL-DGL-FA-ASODN-DCA nanocomposite was about 170-192 nm, and according to the agarose gel retardation assay, the loading amount of ASODN accounted for 166.7 mg/g. The results of cellular uptake showed that the nanocomposite could specifically target to HepG2 and Hela cells. The cytotoxicity assay demonstrated that the toxicity of vectors was greatly reduced by using DCA to reversibly block the cationic DGL. The subcellular distribution images clearly displayed the lysosomal escape ability of the DCA-modified nanocomposite. In vitro exploration of molecular mechanism indicated that the nanocomposite could inhibit mRNA expression and HIF-1α protein translation at different levels. In vivo optical images and quantitative assay testified that the formulation accumulated preferentially in the tumor tissue. In vivo antitumor efficacy research confirmed that this nanocomposite had significant antitumor activity and the tumor inhibitory rate was 77.99%. These results manifested that the GEL-DGL-FA-ASODN-DCA nanocomposite was promising in gene therapeutics for antitumor by interacting directly with target RNA.

Stimuli-Responsive Aliphatic Polycarbonate Nanocarriers for Tumor-Targeted Drug Delivery

Nanoparticles based on amphiphilic copolymers with tunable physicochemical properties can be used to encapsulate delicate pharmaceutics while at the same time improving their solubility, stability, pharmacokinetic properties, reducing immune surveillance, or achieving tumor-targeting ability. Those nanocarriers based on biodegradable aliphatic polycarbonates are a particularly promising platform for drug delivery due to flexibility in the design and synthesis of appropriate monomers and copolymers. Current studies in this field focus on the design and the synthesis of new effective carriers of hydrophobic drugs and their release in a controlled manner by exogenous or endogenous factors in tumor-specific regions. Reactive groups present in aliphatic carbonate copolymers, undergo a reaction under the action of a stimulus: e.g., acidic hydrolysis, oxidation, reduction, etc. leading to changes in the morphology of nanoparticles. This allows the release of the drug in a highly controlled manner and induces a desired therapeutic outcome without damaging healthy tissues. The presented review summarizes the current advances in chemistry and methods for designing stimuli-responsive nanocarriers based on aliphatic polycarbonates for controlled drug delivery.

Cationic polycarbonates via ring-opening polymerization: design, synthesis, and applications

The synthetic methods and applications of cationic polycarbonates via ring-opening polymerization are highlighted.