Impact of Polyethylene Glycol (PEG) Conformations on the In Vivo Fate and Drug Release Behavior of PEGylated Core-Cross-Linked Polymeric Nanoparticles

Bicontinuous Nanoparticles from Spontaneous Self-Assembly of Block Copolymer Prodrug in Aqueous Medium for Potential Cancer Therapy

Despite having several advantages, bicontinuously structured polymeric nanoparticles (BSPNPs) are far less explored in the field of controlled drug delivery owing to the requirement of complex precursor copolymers and the associated multistep synthetic procedures. In this work, we report the synthesis of a redox-sensitive diblock copolymer (P1), which was subsequently utilized to prepare doxorubicin (DOX) containing a pH-labile prodrug (P2). P1 and P2 spontaneously self-assembled in aqueous media above their critical aggregation concentration, forming micellar nanoparticles with rare bicontinuous morphology that promotes loading of both hydrophobic and hydrophilic cargoes in different compartments. To the best of our knowledge, the formation of BSPNPs through direct self-assembly in aqueous media has not yet been reported. In vitro cellular studies asserted the higher safety profile of the nanoparticles against noncancerous cells (HEK293T) than free DOX, whereas they displayed higher drug-induced cytotoxicity against cancer cells (MCF-7) in comparison to free DOX, establishing them as promising cancer drug delivery systems.

Prevention of Protein Adsorption and Macrophage Phagocytosis of Perfluorocarbon-Based Microsized Core-Shell Artificial Oxygen Carriers by Facile PEG Coatings

Polyethylene glycol (PEG)-coated microsized artificial oxygen carriers (AOCs) with a perfluorooctyl bromide (PFOB) core and poly(lactide-co-caprolactone) (PLC) shell were successfully fabricated using Shirasu porous glass (SPG) membrane emulsification. The PEG coating was achieved by adding the polylactide-b-polyethylene glycol-b-polylactide (PLA-PEG-PLA) block copolymer to the disperse phase during the SPG membrane emulsification process. During the DCM evaporation process, the three-layer structure of the PEG layer, PLC shell, and PFOB core of the AOCs spontaneously formed by phase separation. By adjustment of the ratio of PLA to PLA-PEG-PLA, the PEG chain density on the AOC surface was controlled and estimated as 0.1-2.4 chains nm-2 based on quantitative proton nuclear magnetic resonance analysis. It was expected that a loop PEG brush structure was formed on the surface of the AOCs owing to the ABA block copolymer structure of PLA-PEG-PLA. With the increase in PEG chain density, nonspecific adsorption of bovine serum albumin, γ-globulin, and fibrinogen to AOCs decreased drastically and reached below 10 μg cm-2. Additionally, phagocytosis of the AOCs, evaluated using the macrophage cell line RAW 264.7, was effectively prevented and the phagocytosis index decreased from 2 to almost 0. Finally, the PEG-coated core-shell AOCs exhibited excellent higher cell viability to RAW 264.7 than bare AOCs and showed oxygen delivery to hypoxia-responsive HeLa cells. Effective facile PEG coating on PFOB/PLC core-shell AOCs was successfully achieved simultaneously with membrane emulsification and subsequent evaporation-induced phase separation. It will be an effective strategy for membrane emulsification technology as well as the preparation of AOCs.

Click Chemistry for Biofunctional Polymers: From Observing to Steering Cell Behavior

Click chemistry has become one of the most powerful construction tools in the field of organic chemistry, materials science, and polymer science, as it offers hassle-free platforms for the high-yielding synthesis of novel materials and easy functionalization strategies. The absence of harsh reaction conditions or complicated workup procedures allowed the rapid development of novel biofunctional polymeric materials, such as biopolymers, tailor-made polymer surfaces, stimulus-responsive polymers, etc. In this review, we discuss various types of click reactions─including azide-alkyne cycloadditions, nucleophilic and radical thiol click reactions, a range of cycloadditions (Diels-Alder, tetrazole, nitrile oxide, etc.), sulfur fluoride exchange (SuFEx) click reaction, and oxime-hydrazone click reactions─and their use for the formation and study of biofunctional polymers. Following that, we discuss state-of-the-art biological applications of "click"-biofunctionalized polymers, including both passive applications (e.g., biosensing and bioimaging) and "active" ones that aim to direct changes in biosystems, e.g., for drug delivery, antiviral action, and tissue engineering. In conclusion, we have outlined future directions and existing challenges of click-based polymers for medicinal chemistry and clinical applications.

Engineering poly(ethylene glycol) particles for targeted drug delivery

Poly(ethylene glycol) (PEG) is considered to be the "gold standard" among the stealth polymers employed for drug delivery. Using PEG to modify or engineer particles has thus gained increasing interest because of the ability to prolong blood circulation time and reduce nonspecific biodistribution of particles in vivo, owing to the low fouling and stealth properties of PEG. In addition, endowing PEG-based particles with targeting and drug-loading properties is essential to achieve enhanced drug accumulation at target sites in vivo. In this feature article, we focus on recent work on the synthesis of PEG particles, in which PEG is the main component in the particles. We highlight different synthesis methods used to generate PEG particles, the influence of the physiochemical properties of PEG particles on their stealth and targeting properties, and the application of PEG particles in targeted drug delivery.

Antifouling polymers for nanomedicine and surfaces: recent advances

Antifouling polymers are materials that can resist nonspecific interactions with cells, proteins, and other biomolecules. Typically, they are hydrophilic polymers with polar or charged moieties that are capable of strong nonbonding interactions with water molecules. This propensity to bind water generates a surface hydration layer that reduces nonspecific interactions with other molecules and is paramount to the antifouling behavior. This property is especially useful for nanoscale applications such as nanomedicine and surface modifications at the molecular level. In nanomedicine, antifouling polymers such as poly(ethylene glycol) and its alternatives play a key role in shielding drug molecules and therapeutic proteins/genes from the immune system within nanoassemblies, thereby enabling effective delivery to target tissues. For coatings, antifouling polymers help to prevent adhesion of cells and molecules to surfaces and are thus valued in marine and biomedical device applications. In this Review, we survey recent advances in antifouling polymers in the context of nanomedicine and coatings, while shining the spotlight on the major polymer classes such as PEG, polyzwitterions, poly(oxazoline)s, and other nonionic hydrophilic polymers.

Polymeric core-crosslinked particles prepared via a nanoemulsion-mediated process: from particle design and structural characterization to in vivo behavior in chemotherapy

Various polymeric nanoparticles have been used as drug carriers in drug delivery systems (DDSs). Most of them were constructed from dynamic self-assembly systems formed via hydrophobic interactions and from structures that are unstable in an in vivo environment owing to their relatively weak formation forces. As a solution to this issue, physically stabilized core-crosslinked particles (CP) with chemically crosslinked cores have received attention as alternatives to the dynamic nanoparticles. This focused review summarizes recent advances in the construction, structural characterization, and in vivo behavior of polymeric CPs. First, we introduce a nanoemulsion-mediated method to create polyethylene glycol (PEG)-bearing CPs and their structural characterization. The relationship between the PEG chain conformations in the particle shell and the in vivo fate of the CPs is also discussed. After that, the development and advantages of zwitterionic amino acid-based polymer (ZAP)-bearing CPs are presented to address the poor penetration and the internalization of PEG-based CPs into tumor tissues and cells, respectively. Finally, we conclude and discuss prospects for application of polymeric CPs in the DDS field.

Advances of Antimicrobial Peptide-Based Biomaterials for the Treatment of Bacterial Infections

Owing to the increase in multidrug-resistant bacterial isolates in hospitals globally and the lack of truly effective antimicrobial agents, antibiotic resistant bacterial infections have increased substantially. There is thus an urgent need to develop new antimicrobial drugs and their related formulations. In recent years, natural antimicrobial peptides (AMPs), AMP optimization, self-assembled AMPs, AMP hydrogels, and biomaterial-assisted delivery of AMPs have shown great potential in the treatment of bacterial infections. In this review, it is focused on the development prospects and shortcomings of various AMP-based biomaterials for treating animal model infections, such as abdominal, skin, and eye infections. It is hoped that this review will inspire further innovations in the design of AMP-based biomaterials for the treatment of bacterial infections and accelerate their commercialization.

Anchoring of Polymer Loops on Enzyme-Immobilized Mesoporous ZIF-8 Enhances the Recognition Selectivity of Angiotensin-Converting Enzyme Inhibitory Peptides

Immobilized angiotensin-converting enzyme (ACE) is a promising material for the rapid screening of antihypertensive drugs, but the nonspecific adsorption is a serious problem in separation processes involving complex biological products. In this study, triblock copolymers with dopamine (DA) block as anchors and PEG block as the main body (DA-PEGx-DA) were attached to an immobilized ACE (ACE@mZIF-8/PDA, AmZP) surface via the “grafting to” strategy which endowed them with anti-nonspecific adsorption. The influence of DA-PEGx-DA chain length on nonspecific adsorption was confirmed. The excellent specificity and reusability of the obtained ACE@mZIF-8/PDA/DA-PEG5000-DA (AmZPP5000) was validated by screening two known ACE inhibitory peptides Val-Pro-Pro (VPP, competitive inhibitory peptides of ACE) and Gly-Met-Lys-Cys-Ala-Phe (GF-6, noncompetitive inhibitory peptides of ACE) from a mixture containing active and inactive compounds. These results demonstrate that anchored polymer loops are effective for high-recognition selectivity and AmZPP5000 is a promising compound for the efficient separation of ACE inhibitors in biological samples.