pH-triggered PMAA-b-HTPB-b-PMAA copolymer micelles: physicochemical characterization and camptothecin release

Hydroxyl-Terminated Polybutadiene-Based Polyurethane with Self-Healing and Reprocessing Capabilities

Hydroxyl-terminated polybutadiene (HTPB)-based polyurethane (PU) networks play indispensable roles in a variety of applications; however, they cannot be reprocessed, resulting in environmental problems and unsustainable industrial development. In this work, recyclable HTPB-based PU vitrimer (HTPB-PU_V) networks are fabricated by introduction of a cross-linker 2,2'-(1,4-phenylene)-bis[4-mercaptan-1,3,2-dioxaborolane] (BDB) with dynamic boronic ester bonds into the network. Meanwhile, the BDB can stabilize the HTPB unit in the network by elimination of double bonds. The novel HTPB-PU_V networks are constructed by a thiol-ene "click" reaction and an addition reaction between HTPB and cross-linker BDB and isocyanates (HDI). The dynamic HTPB-PU_V networks are characterized by dynamic mechanical analysis (DMA) and Fourier transform infrared (FTIR). The obtained dynamic HTPB-PU_V networks possess superior thermostability. Moreover, due to the presence of dynamic boronic ester bonds, the HTPB-PU_V network topologies can be altered, contributing to the reprocessing, self-healing, and welding abilities of the final polymer. Through a hot press, the pulverized sample can be reprocessed for several cycles, and mechanical properties of the reprocessed samples are similar to those of the pristine one, with the tensile strength being even higher. The self-healed sample exhibits almost complete recovery from scratch after the healing treatment at 130 °C for 3 h. Moreover, a welding efficiency of 120% was achieved.

Preparation of Ligand Brush Nanocapsules for Robust Self-Controlled Antimicrobial Activity with Low Cytotoxicity at Target pH and Humidity

This study prepared nanocapsules (NCs) with excellent self-controlled antimicrobial activity at pH 6–7 and humidity 45–100%, conditions in which most bacterial and fungal strains thrive. The nanocapsule substrate (NC@SiO₂) was 676 nm in diameter, and the ligand-grafted capsule (NC@SiO₂-g-MAA) was 888 nm. The large surface area and outer ligand brush of the NCs induced a rapid, self-controlled antibacterial response in the pH and humidity conditions needed for industrial and medical applications. Ligand-brush NCs containing an anionic antimicrobial drug had a rapid release effect because of the repellent electrostatic force and swelling properties of the ligand brushes. Controlled release of the drug was achieved at pH 6 and humidity of 45% and 100%. As many carboxylic acid groups are deprotonated into carboxylic acids at pH 5, the NC@SiO₂-g-MAA had a high negative charge density. Carboxylic acid groups are anionized (–COO⁻) at pH 6 and above and push each other out of the capsule, expanding the outer shell as in a polymer brush to create the release behavior. The surface potential of the NC intermediate (NC@SiO₂-MPS) was −23.45 [mV], and the potential of the capsule surface decreased to −36.4 [mV] when the MAA ligand brushes were grafted onto the surface of the capsule intermediate. In an antimicrobial experiment using Escherichia coli, a clear zone of 13–20 mm formed at pH 6, and the E. coli was eradicated completely at pH 6 and pH 7 when the humidity was 100%.

Amino acid-derived ABCBA-type antifouling biohybrid with multi-stimuli responsivity and contaminant removal capability

A multi-stimuli (pH/thermo/redox)-responsive amphiphilic poly(cysteine methacrylamide)-block-poly(N,N-dimethylaminoethyl methacrylate)-block-polybutadiene-block-poly(N,N-dimethylaminoethyl methacrylate)-block-poly(cysteine methacrylamide) (PCysMAM-b-PDMAEMA-b-PB-b-PDMAEMA-b-PCysMAM) pentablock copolymer biohybrids, based on hydrophobic PB, ampholytic redox responsive PCysMAM and dual (pH and temperature) stimuli responsive PDMAEMA segments,...

l-Histidine-Derived Smart Antifouling Biohybrid with Multistimuli Responsivity

A novel dual pH/thermoresponsive amphiphilic poly(histidine methacrylamide)-block-hydroxyl-terminated polybutadiene-block-poly(histidine methacrylamide) (PHisMAM-b-PB-b-PHisMAM) triblock copolymer biohybrid, composed of hydrophobic PB and ampholytic PHisMAM segments, is developed via direct switching from living anionic polymerization to recyclable nanoparticle catalyst-mediated reversible-deactivation radical polymerization (RDRP). The transformation involved in situ postpolymerization modification of living polybutadiene-based carbanionic species, end-capped with ethylene oxide, into dihydroxyl-terminated polybutadiene and a subsequent reaction with 2-bromo-2-methylpropionyl bromide resulting in a telechelic ATRP macroinitiator (Br-PB-Br). Br-PB-Br was used to mediate RDRP of an l-histidine-derived monomer, HisMAM, yielding a series of PHisMAM-b-PB-b-PHisMAM triblock copolymers. The copolymer's stimuli response was assessed against pH and temperature changes. The copolymer is capable of switching among its zwitterionic, anionic, and cationic forms and exhibited unique antifouling properties in its zwitterionic form. These novel triblock copolymers are expected to be show promising potential in biomedical applications.

Polymeric micelles for the delivery of poorly soluble drugs: From nanoformulation to clinical approval

Over the last three decades, polymeric micelles have emerged as a highly promising drug delivery platform for therapeutic compounds. Particularly, poorly soluble small molecules with high potency and significant toxicity were encapsulated in polymeric micelles. Polymeric micelles have shown improved pharmacokinetic profiles in preclinical animal models and enhanced efficacy with a superior safety profile for therapeutic drugs. Several polymeric micelle formulations have reached the clinical stage and are either in clinical trials or are approved for human use. This furthers interest in this field and underscores the need for additional learning of how to best design and apply these micellar carriers to improve the clinical outcomes of many drugs. In this review, we provide detailed information on polymeric micelles for the solubilization of poorly soluble small molecules in topics such as the design of block copolymers, experimental and theoretical analysis of drug encapsulation in polymeric micelles, pharmacokinetics of drugs in polymeric micelles, regulatory approval pathways of nanomedicines, and current outcomes from micelle formulations in clinical trials. We aim to describe the latest information on advanced analytical approaches for elucidating molecular interactions within the core of polymeric micelles for effective solubilization as well as for analyzing nanomedicine's pharmacokinetic profiles. Taking into account the considerations described within, academic and industrial researchers can continue to elucidate novel interactions in polymeric micelles and capitalize on their potential as drug delivery vehicles to help improve therapeutic outcomes in systemic delivery.

Genus Ophiorrhiza: A Review of Its Distribution, Traditional Uses, Phytochemistry, Biological Activities and Propagation

Almost 50 species of Ophiorrhiza plants were reviewed in this work and the main objective is to critically analyse their distribution, phytochemical content, biological activity, and propagation. Moreover, the information would be useful in promoting the relevant uses of the plant, especially in the medicinal fields based on in vitro and in vivo studies. To this end, scientific sources, including theses, PubMed, Google Scholar, International Islamic University Malaysia IIUM EBSCO, PubChem, and Elsevier, were accessed for publications regarding the Ophiorrhiza genus in this review. Scientific literature regarding the Ophiorrhiza plants revealed their wide distribution across Asia and the neighbouring countries, whereby they were utilised as traditional medicine to treat various diseases. In particular, various active compounds, such as alkaloids, flavonoids, and terpenoids, were reported in the plant. Furthermore, the Ophiorrhiza species showed highly diverse biological activities, such as anti-cancer, antiviral, antimicrobial, and more. The genus propagation reported could produce a high quality and quantity of potent anticancer compound, namely camptothecin (CPT). Hence, it is believed that the relevant uses of natural compounds present in the plants can replace the existing crop of synthetic anticancer drugs associated with a multitude of unbearable side effects. Additionally, more future studies on the Ophiorrhiza species should be undertaken to establish the links between its traditional uses, active compounds, and pharmacological activities reported.

Injectable Hydrogel of Vitamin B9 for the Controlled Release of Both Hydrophilic and Hydrophobic Anticancer Drugs

Folic acid (FA), vitamin B₉ , is a good receptor of drugs triggering cellular uptake via endocytosis. FA is sparingly soluble in water. Herein, a new approach for the formation of FA hydrogel by the hydrolysis of glucono-δ-lactone in PBS buffer under physiological conditions has been reported. The gel has a fibrillar network morphology attributable to intermolecular H-bonding and π-stacking interactions. The thixotropic property of the gel is used for the encapsulation of both hydrophilic [doxorubicin (DOX)] and hydrophobic [camptothecin (CPT)] drugs. The loading of DOX and CPT into the gel is attributed to the H-bonding interaction between FA and drugs. The release of DOX is sustainable at pH 4 and 7, and the Peppas model indicates that at pH 7 the diffusion of the drug is Fickian but it is non-Fickian at pH 4. The release of CPT is monitored by fluorescence spectroscopy, which also corroborates the combined release of both drugs. The metylthiazolyldiphenyltetrazolium bromide assay of FA hydrogel demonstrates nontoxic behavior and that the cytotoxicity of the DOX-loaded FA hydrogel is higher than that of pure DOX, with a minimal effect on normal cells.

Polymeric micelles: Basic research to clinical practice

Rapidly developing polymeric micelles as potential targeting carriers has intensified the need for better understanding of the underlying principles related to the selection of suitable delivery materials for designing, characterizing, drug loading, improving stability, targetability, biosafety and efficacy. The emergence of advanced analytical tools such as fluorescence resonance energy transfer and dissipative particle dynamics has identified new dimensions of these nanostructures and their behavior in much greater details. This review summarizes recent efforts in the development of polymeric micelles with respect to their architecture, formulation strategy and targeting possibilities along with their preclinical and clinical aspects. Literature of the past decade is discussed critically with special reference to the chemistry involved in the formation and clinical applications of these versatile materials. Thus, our main objective is to provide a timely update on the current status of polymeric micelles highlighting their applications and the important parameters that have led to successful delivery of drugs to the site of action.

Impact of hydrogenation on physicochemical and biomedical properties of pH-sensitive PMAA-b-HTPB-b-PMAA triblock copolymer drug carriers

pH-Sensitive poly(methacrylic acid)-block-hydroxyl-terminated polybutadiene-block-poly(methacrylic acid) (PMAA-b-HTPB-b-PMAA) was synthesized and then hydrogenated in this work. The chain structure, phase behavior and thermal properties were characterized by(1)H NMR, FTIR, XRD, DSC, TGA, etc., and the physicochemical and biomedical properties were investigated via fluorescence spectroscopy, TEM, DLS, loading and release of drug and MTT, and so on. The experimental results indicated that the hydrogenation led to the change in the chain aggregate structure of hydrophobic HTPB blocks and the formation of more stable spherical core-shell micelle aggregates, and the critical micelle concentration decreased from 41.8 mg L(-1)before hydrogenation to 4.4 mg L(-1)after hydrogenation. The hydrogenated block copolymer micelle aggregates exhibited pH-triggered response, and could entrap twice as much hydrophobic drug as the unhydrided counterparts and the encapsulation efficiency was significantly improved, which makes them fine to meet the requirements for drug carriers. Therefore, the hydrogenated PMAA-b-HTPB-b-PMAA copolymer micelles as drug target release carriers can be well used in the field of prevention and treatment of cancers.

Core crosslinked H-type poly(methacrylic acid)-block-hydroxyl terminated polybutadiene-block-poly(methacrylic acid) four-armed star block copolymer micelles for intercellular drug release

H-type four-armed star block copolymers with hydroxyl-terminated polybutadiene as hydrophobic sections and poly(methacrylic acid) as hydrophilic fragments were synthesized through atom transform radical polymerization and the follow-up acidolysis, named PMAA2- b-HTPB- b-PMAA2. The core crosslinking reaction was conducted by ultraviolet light irradiation. 1H nuclear magnetic resonance, Fourier transform infrared, size exclusion chromatography, and thermal gravimetric analysis were adopted to confirm the chemical structure of the resulting copolymers. The effect of the ultraviolet light crosslinking on the physicochemical properties of the block copolymer micelles was investigated by fluorescent spectrometry, ultraviolet transmittance, dynamic light scattering, and transmission electron microscope measurements. The results showed that the crosslinking resulted in formation of the stable copolymer micelles and change in the physicochemical parameters, for example, lower critical micelle concentration and smaller micellar size than the uncrosslinked one. Drug loading and in vitro drug release disclosed that the crosslinked copolymer micelles had enhanced drug loading capacity and encapsulation efficiency, less drug leakage, and thus smaller harm to the normal cells but better therapy effect than the uncrosslinked counterpart by the aid of the pH-induced paclitaxel release. The copolymer micelles exhibited pH-dependent cytotoxicity, and therefore, they might be a promising drug target release carrier in biomedical applications.