Multiple Pickering emulsions stabilized by surface-segregated micelles with adaptive wettability

Surface-segregated micelles (SSMs) with adaptive wettability have considerable potential for application in Pickering emulsions and bioanalytical technology. In this study, spherical SSMs were prepared via polymerization-induced self-assembly co-mediated with a binary mixture of macromolecular chain transfer agents: pH-responsive poly(2-(dimethylamino) ethyl methacrylate) and hydrophobic polydimethylsiloxane. Using these SSMs as the sole emulsifier, we adjusted the pH to successfully produce both water-in-oil-in-water (W/O/W) and oil-in-water-in-oil (O/W/O) multiple emulsions through a single-step emulsification process. Moreover, we demonstrated that multiple emulsion systems with adjustable pH are suitable for the development of an efficient and recyclable interfacial catalytic system. Multiple emulsion microreactors increase the area of the oil–water interface and are therefore more efficient than the commonly used O/W and W/O emulsion systems.

Surface-segregated micelles (SSMs) with adaptive wettability have considerable potential for application in Pickering emulsions and microreactors.

Organic/Inorganic Self-Assembled Hybrid Nano-Architectures for Cancer Therapy Applications

Since the conceptualization of nanomedicine, numerous nanostructure-mediated drug formulations have progressed into clinical trials for treating cancer. However, recent clinical trial results indicate such kind of drug formulations has a limited improvement on the antitumor efficacy. This is due to the biological barriers associated with those formulations, for example, circulation stability, extravasation efficiency in tumor, tumor penetration ability, and developed multi-drug resistance. When employing for nanomedicine formulations, pristine organic-based and inorganic-based nanostructures have their own limitations. Accordingly, organic/inorganic (O/I) hybrids have been developed to integrate the merits of both, and to minimize their intrinsic drawbacks. In this context, the recent development in O/I hybrids resulting from a self-assembly strategy will be introduced. Through such a strategy, organic and inorganic building blocks can be self-assembled via either chemical covalent bonds or physical interactions. Based on the self-assemble procedure, the hybridization of four organic building blocks including liposomes, micelles, dendrimers, and polymeric nanocapsules with five functional inorganic nanoparticles comprising gold nanostructures, magnetic nanoparticles, carbon-based materials, quantum dots, and silica nanoparticles will be highlighted. The recent progress of these O/I hybrids in advanced modalities for combating cancer, such as, therapeutic agent delivery, photothermal therapy, photodynamic therapy, and immunotherapy will be systematically reviewed.

Polymeric approach to combat drug-resistant methicillin-resistant Staphylococcus aureus

ABSTRACT

The current global death rate has threatened humans due to increase in deadly unknown infections caused by pathogenic microorganisms. On the contrary, the emergence of multidrug-resistant bacteria is also increasing which is leading to elevated lethality rate worldwide. Development of drug-resistant bacteria has become one of the daunting global challenges due to failure in approaching to combat against them. Methicillin-resistant Staphylococcus aureus (MRSA) is one of those drug-resistant bacteria which has led to increase in global mortality rate causing various lethal infections. Polymer synthesis can be one of the significant approaches to combat MRSA by fabricating polymeric coatings to prevent the spread of infections. This review provides last decade information in the development of various polymers against MRSA.

GRAPHICAL ABSTRACT

Safe and efficient membrane permeabilizing polymers based on PLLA for antibacterial applications

Highly active antibacterial poly(N,N-dimethylaminoethyl methacrylate)-block-poly(l-lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) conjugated with poly(ethylene glycol) (D-PLLA-D@PEG) copolymers were synthesized.

Preparation and properties of P(AN-co-AM)-g-MAPEG phase-change nanofibers

In this study, a new graft copolymer, P(AN- co-AM)- g-MAPEG, was synthesized by polyethylene glycol monoester of maleic acid (MAPEG), acrylonitrile (AN), and a third monomer acrylamide (AM) in water phase precipitation, in which random copolymer of P(AN- co-AM) was taken as skeleton and macromonomer MAPEG with phase transition as branched chain. The P(AN- co-AM)- g-MAPEG nanofibers were prepared by electrostatic spinning. The effects of pinhole diameter, spinning solution concentration, and spinning liquid solvent on the structure of nanofibers were investigated by scanning electron microscopy. The structure, phase-change properties, and thermal stability of the grafted copolymer were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction. The results show that the new solid–solid phase-change material P(AN- co-AM)- g-MAPEG was successfully prepared. The nanofiber diameter increased with the increasing pinhole diameter. The obtained phase-change nanofibers exhibit good phase transition and thermal stability.

Nanocapsules templated on liquid cores stabilized by graft amphiphilic polyelectrolytes

A surfactant-free method of preparation of nanocapsules templated on liquid cores using amphiphilic graft polyelectrolytes was developed. A model photoactive copolymer, poly(sodium 2-acrylamido-2-methyl-1-propanesulfonate) with grafted poly(vinylnaphthalene) chains (PAMPS-graft-PVN) was used to stabilize toluene droplets in an aqueous emulsion. The macromolecules, due to their amphiphilic character and the presence of strong ionic groups, tend to undergo intramolecular aggregation in water but at the water-oil interface less compact conformation is preferred with PVN grafts anchoring in the oil phase and the charged PAMPS main chains residing in the aqueous phase, thus stabilizing the nanoemulsion droplets. Formation of such nanocapsules was confirmed by dynamic light scattering measurements as well as SEM and cryo-TEM imaging. Grafting density and content of the chromophores in the graft copolymers were varied in order to achieve high stability of the coated nanodroplets. It was shown that the capsules are better stabilized by the copolymers with many short hydrophobic grafts than with fewer but longer ones. Use of photoactive polyelectrolytes enabled spectroscopic investigation of the relationship between conformation of the macromolecules and stabilization of the oil-core nanocapsules. Long-term stability of the nanocapsules was achieved and further increased by multilayer shell formation using polyelectrolytes deposited via the layer-by-layer approach. The obtained capsules served as efficient nanocontainers for a hydrophobic fluorescent probe. The proposed strategy of nanocapsule preparation may be easily extended to biologically relevant polymers and applied to fabricate liquid core nanodelivery systems without the need of using low molecular weight additives which may have adverse effects in numerous biomedical applications.

Poly(ethylene glycol) conjugated poly(lactide)-based polyelectrolytes: synthesis and formation of stable self-assemblies induced by stereocomplexation

A series of pH-responsive amphiphilic poly(N,N-dimethylaminoethyl methacrylate)-block-poly(D-lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) conjugated with poly(ethylene glycol) (D-PDLA-D@PEG) and D-PLLA-D@PEG copolymers were synthesized using a combination of ring-opening polymerization and atom-transfer radical polymerization followed by sequential quaternization of PDMAEMA chains and azide-alkyne click reaction with alkyne-end PEG. Gel permeation chromatography, nuclear magnetic resonance, and Fourier transform infrared spectroscopy results demonstrate the successful synthesis of the copolymers, and the conjugated PEG percentages in the copolymers can be tuned by the feeding ratios in the quaternization reaction. Conjugating PEG onto the PDMAEMA segments also successfully facilitated the D-PDLA-D@PEG, D-PLLA-D@PEG, and its corresponding 1:1 D/L mixtures to be dissolved directly in aqueous solution at the desired concentration range without using any organic solvents unlike the copolymers without PEG conjugation (D-PDLA-D and D-PLLA-D). We demonstrate control over micellar size, charge, and stability via three different preparation pathways, i.e., solution pH, percentages of PEG conjugation in the copolymers, and formation of PLA stereocomplex in micellar core. Static and dynamic light scattering studies demonstrate that the size of the core-shell micelles increases when the solution pH is reduced due to the protonation of the PDMAEMA segments that caused the osmotic pressure within the micelle to increase until the micelles reached a maximum size. It is interesting to note that the micelles formed by 1:1 D/L mixtures have larger swelling ratios as well as aggregation number and hydrodynamic radius that do not change significantly with pH and dilution, respectively, as compared to micelles formed from individual D or L forms of the copolymers. The enhanced stability of the pH-responsive micelles prepared by direct dissolution of the 1:1 D/L mixtures of the PEG conjugated PLA-based polyelectrolytes in aqueous medium is attributed to the stereocomplex formation between PLLA and PDLA in the micellar core as confirmed by wide-angle X-ray scattering measurements.

Recent progress in designing shell cross-linked polymer capsules for drug delivery

This tutorial review highlights the progress made during recent years in the development of the shell cross-linked (SCL) polymer nanocapsules and the impact of the most important scientific ideas on this field of knowledge.

Remarkable efficacy of graft block copolymers as surfactants for reducing interfacial tension

This work provides a standard model for experimental applications of graft copolymers as surfactants, especially for reducing the interfacial tension.