Modulating the Thermoresponsive Characteristics of PLGA-PEG-PLGA Hydrogels via Manipulation of PLGA Monomer Sequences

Hydrogels are promising materials for biomedical applications, particularly in drug delivery and tissue engineering. This study highlights thermoresponsive hydrogels, specifically poly(lactic-co-glycolic acid) (PLGA)-poly(ethylene glycol) (PEG)-PLGA triblock copolymers, and introduces a feed rate-controlled polymerization (FRCP) method. By utilizing an organic catalyst and regulating the monomer feed rate, the sequence distribution of PLGA within the triblock copolymer is controlled. Various analyses, including 13C NMR and rheological measurements, were conducted to investigate the impact of sequence distribution. Results show that altering sequence distribution significantly influences the sol-gel transition, hydrophobicity-hydrophilicity balance, and drug release profile. Increased sequence uniformity lowers the glass transition temperature, raises the sol-gel transition temperature due to enhanced hydrophilicity, and promotes a more uniform drug (curcumin) distribution within the PLGA domain, resulting in a slower release rate. This study emphasizes the importance of PLGA sequence distribution in biomedical applications and the potential of FRCP to tailor thermoresponsive hydrogels for biomedical advancements.

Strategy for Synthesis of Statistically Sequence-Controlled Uniform PLGA and Effects of Sequence Distribution on Interaction and Drug Release Properties

Extensive studies have been conducted to elucidate the effects of such parameters as molecular weight, polydispersity, and composition on the controlled release properties of poly(d,l-lactic-co-glycolic acid) (PLGA). However, studies dealing with the effect of monomer sequence distribution have been sparse mainly because of the difficulty of precisely controlling the monomer sequence in PLGA. Herein, we present a semibatch copolymerization strategy that enables the production of statistically sequence-controlled "uniform PLGA" polymers through control of the rate of comonomer addition. Using this method, a series of PEG-PLGA samples having a comparable molecular weight and composition but different sequence distributions (uniform vs gradient) were prepared. The properties of these materials (PEG crystallization/melting, hygroscopicity, aqueous sol-gel transition, drug release kinetics) were found to significantly vary, demonstrating that sequence control only at the statistical level still significantly influences the properties of PLGA. Most notably, uniform PLGA exhibited the more sustained drug release behavior compared to gradient PLGA.

Localized delivery of active targeting micelles from nanofibers patch for effective breast cancer therapy

Nanofibers based transdermal drug delivery is a promising platform, and it effectively delivers the drug to tumor sites. The objective of the study was to fabricate stimuli-responsive polymeric nanofibers encapsulated with an active targeting micellar system for in situ drug delivery. Stimuli-responsive core-shell nanofibers release thedrug at target sites with minimum side effects to the other organs, decrease the drug administration concentration. Initially, we prepared CA conjugated PCPP polymeric micelles loaded with PTX. Then, core-shell nanofibers were prepared using PHM with coaxial electrospinning and distinct core-shell nanofibers formation confirm by SEM and TEM. Nanofibers showed a homogenous distribution of micelles inside the fiber mesh, diffusion, and erosion processes lead to a controlled release of PTX.In vitro drug release and swelling, revealed the pH based sustained release of the drug for 180 h from the nanofibers mat. Functional and stimuli-responsive nanofibers highly absorb H⁺ ions and repulsion of cations promoting maximum swelling to release more drugs in acidic pH. An increased transportation rate of 70% drug release through epidermis for 120 h. Nanofibers effectively internalize to the skin, and it confirmed by confocal microscopy. MCF-7 cells grown and spread over the nanofibers, which show the biocompatibility of nanofibers. Compared to PTX, drug-loaded nanofibers exhibited higher cytotoxicity for 8 days which was confirmed by the flow cytometry. These promising results confirm, the novel stimuli-responsive core-shell nanofibers actively target breast cancer cells and lead the way to safe cancer therapy.

Polymer Nanosheet Containing Star-Like Copolymers: A Novel Scalable Controlled Release System

Poly(ε-caprolactone) (PCL)-based nanomaterials, such as nanoparticles and liposomes, have exhibited great potential as controlled release systems, but the difficulties in large-scale fabrication limit their practical applications. Among the various methods being developed to fabricate polymer nanosheets (PNSs) for different applications, such as Langmuir-Blodgett technique and layer-by-layer assembly, are very effort consuming, and only a few PNSs can be obtained. In this paper, poly(ε-caprolactone)-based PNSs with adjustable thickness are obtained in large quantity by simple water exposure of multilayer polymer films, which are fabricated via a layer multiplying coextrusion method. The PNS is also demonstrated as a novel controlled guest release system, in which release kinetics are adjustable by the nanosheet thickness, pH values of the media, and the presence of protecting layers. Theoretical simulations, including Korsmeyer-Peppas model and Finite-element analysis, are also employed to discern the observed guest-release mechanisms.

Synthesis of well-defined carboxyl poly(ε-caprolactone) by fine-tuning the protection group

Carboxyl functionalized polycaprolactone with a well-defined structure was synthesized via ring-opening polymerization (ROP) of substituted caprolactone monomer and acidic hydrolysis.