Thermally reversible hydrogels printing of customizable bio-channels with curvature

Replicating intricate bio-channels, akin to expansive vascular networks, offers numerous advantages including self-repair, replacing damaged bio-channels, testing drugs, and biomedical devices. But, crafting multi-sized, editable bio-channels with specific curvatures, particularly using natural polymer-based bio-inks, poses a significant challenge. To address this, this study introduces a temperature-driven indirect printing method, exemplified by the diploic vein. Here, K-carrageenan (kca)-silk fiber (SF)-hyaluronic acid (HA)/hFOB 1.19 (SV40 transfection of human osteoblasts) and kca-collagen-HA/HUVECs (human umbilical vein endothelial cells) are employed to fabricate vascular-like walls and lumens, utilizing their thermoreversible properties to create multi-stage bifurcated lumens. Precise spatial curvature was generated by heating the vascular network wrapped in poly(N-isopropyl acrylamide) (PNIPAAm)-poly(ethylene glycol) diacrylate (PEGDA). Since temperature is specific to the thermal material carrying the cells, the rheological properties of bioinks, modeling temperature parameters, and their impact on printing size was explored. Additionally, mechanical properties and curvature response were characterized to determine the necessary process parameters for achieving the desired size. Ultimately, in vitro bioprinting experiments involving HUVECs and hFOB 1.19 demonstrate cell viability, adhesion, proliferation, and migration within the intraluminal hydrogel scaffold. This approach allows for customizing bio-channel content and controlling curvature programming, providing new prospects for in vitro biochannel production, with potential benefits for pathology research.

Amphiphilic Polyphosphonate Copolymers as New Additives for PDMS-Based Antifouling Coatings

Poly(ethyl ethylene phosphonate)-based methacrylic copolymers containing polysiloxane methacrylate (SiMA) co-units are proposed as surface-active additives as alternative solutions to the more investigated polyzwitterionic and polyethylene glycol counterparts for the fabrication of novel PDMS-based coatings for marine antifouling applications. In particular, the same hydrophobic SiMA macromonomer was copolymerized with a methacrylate carrying a poly(ethyl ethylene phosphonate) (PEtEPMA), a phosphorylcholine (MPC), and a poly(ethylene glycol) (PEGMA) side chain to obtain non-water soluble copolymers with similar mole content of the different hydrophilic units. The hydrolysis of poly(ethyl ethylene phosphonate)-based polymers was also studied in conditions similar to those of the marine environment to investigate their potential as erodible films. Copolymers of the three classes were blended into a condensation cure PDMS matrix in two different loadings (10 and 20 wt%) to prepare the top-coat of three-layer films to be subjected to wettability analysis and bioassays with marine model organisms. Water contact angle measurements showed that all of the films underwent surface reconstruction upon prolonged immersion in water, becoming much more hydrophilic. Interestingly, the extent of surface modification appeared to be affected by the type of hydrophilic units, showing a tendency to increase according to the order PEGMA < MPC < PEtEPMA. Biological tests showed that Ficopomatus enigmaticus release was maximized on the most hydrophilic film containing 10 wt% of the PEtEP-based copolymer. Moreover, coatings with a 10 wt% loading of the copolymer performed better than those containing 20 wt% for the removal of both Ficopomatus and Navicula, independent from the copolymer nature.

Effect of Polymer Hydrophilicity and Molar Mass on the Properties of the Protein in Protein-Polymer Conjugates: The Case of PPEylated Myoglobin

Polyphosphoesters (PPEs), a versatile class of biodegradable and biocompatible polymers, have been proposed as alternatives to poly(ethylene glycol) (PEG), which is suspected to be responsible for anaphylactic reactions in some patients after the administration of PEGylated compounds, e.g., in the current Covid-19 vaccines. We present the synthesis and characterization of a novel set of protein-polymer conjugates using the model protein myoglobin and a set of PPEs with different hydrophilicity and molar mass. We report an extensive evaluation of the (bio)physical properties of the protein within the conjugates, studying its conformation, residual activity, and thermal stability by complementary techniques (UV-vis spectroscopy, nano-differential scanning calorimetry, and fluorometry). The data underline the systematic influence of polymer hydrophilicity on protein properties. The more hydrophobic polymers destabilize the protein, the more hydrophilic PPEs protect against thermally induced aggregation and proteolytic degradation. This basic study aims at guiding the design of future PPEylated drugs and protein conjugates.

Recent Advances in Stimuli-Responsive Commodity Polymers

Known for their adaptability to surroundings, capability of transport control of molecules, or the ability of converting one type of energy to another as a result of external or internal stimuli, responsive polymers play a significant role in advancing scientific discoveries that may lead to an array of diverge applications. This review outlines recent advances in the developments of selected commodity polymers equipped with stimuli-responsiveness to temperature, pH, ionic strength, enzyme or glucose levels, carbon dioxide, water, redox agents, electromagnetic radiation, or electric and magnetic fields. Utilized diverse applications ranging from drug delivery to biosensing, dynamic structural components to color-changing coatings, this review focuses on commodity acrylics, epoxies, esters, carbonates, urethanes, and siloxane-based polymers containing responsive elements built into their architecture. In the context of stimuli-responsive chemistries, current technological advances as well as a critical outline of future opportunities and applications are also tackled.

Nanoscopic Dynamics Dictate the Phase Separation Behavior of Intrinsically Disordered Proteins

Many intrinsically disordered proteins (IDPs) in nature may undergo liquid-liquid phase separation to assemble membraneless organelles with varied liquid-like properties and stability/dynamics. While solubility changes underlie these properties, little is known about hydration dynamics in phase-separating IDPs. Here, by studying IDP polymers of similar composition but distinct liquid-like dynamics and stability upon separation, namely, thermal hysteresis, we probe at a nanoscopic level hydration/dehydration dynamics in IDPs as they reversibly switch between phase separation states. Using continuous-wave electron paramagnetic resonance (CW EPR) spectroscopy, we observe distinct backbone and amino acid side-chain hydration dynamics in these IDPs. This nanoscopic view reveals that side-chain rehydration creates a dynamic water shield around the main-chain backbone that effectively and counterintuitively prevents water penetration and governs IDP solubility. We find that the strength of this superficial water shell is a sequence feature of IDPs that encodes for the stability of their phase-separated assemblies. Our findings expose and offer an initial understanding of how the complexity of nanoscopic water-IDP interactions dictate their rich phase separation behavior.

Cyclic ethylene phosphates with (CH2)nCOOR and CH2CONMe2 substituents: synthesis and mechanistic insights of diverse reactivity in aryloxy-Mg complex-catalyzed (co)polymerization

Herein we present a comparative study of the reactivity of ethylene phosphates with –O(CH2)nCOOMe (n = 1–3, 5), –CH2COOtBu, –OCHMeCOOMe, and –OCH2CONMe2 substituents in BHT-Mg catalyzed ROP.

Main-Chain Phosphorus-Containing Polymers for Therapeutic Applications

Polymers in which phosphorus is an integral part of the main chain, including polyphosphazenes and polyphosphoesters, have been widely investigated in recent years for their potential in a number of therapeutic applications. Phosphorus, as the central feature of these polymers, endears the chemical functionalization, and in some cases (bio)degradability, to facilitate their use in such therapeutic formulations. Recent advances in the synthetic polymer chemistry have allowed for controlled synthesis methods in order to prepare the complex macromolecular structures required, alongside the control and reproducibility desired for such medical applications. While the main polymer families described herein, polyphosphazenes and polyphosphoesters and their analogues, as well as phosphorus-based dendrimers, have hitherto predominantly been investigated in isolation from one another, this review aims to highlight and bring together some of this research. In doing so, the focus is placed on the essential, and often mutual, design features and structure-property relationships that allow the preparation of such functional materials. The first part of the review details the relevant features of phosphorus-containing polymers in respect to their use in therapeutic applications, while the second part highlights some recent and innovative applications, offering insights into the most state-of-the-art research on phosphorus-based polymers in a therapeutic context.

Surface Grafting Polyphosphoesters on Cellulose Nanocrystals To Improve the Emulsification Efficacy

Particle-stabilized emulsion systems have been developed to address the problematic properties of conventional surfactants. However, the nature and properties of the fine particles used in such systems remain a critical issue for stability enhancement. Herein, we describe a thermoswitchable oil-in-water (O/W) particle-stabilized emulsion that exhibits improved stability due to the addition of cellulose nanocrystals (CNCs) modified with poly[2-isopropoxy-2-oxo-1,3,2-dioxaphospholane] (PIPP), which exhibits relatively good biocompatibility and biodegradability. Various parameters, such as surface activity, concentration of particles, polarity of solvents, and temperatures, on the formation of emulsions with CNCs grafted with PIPP (CNC-g-PIPP) were investigated. Results showed that the surface activity of CNC-g-PIPP was significantly improved compared with the unmodified material. Heptane-in-water particle-stabilized emulsions with CNC-g-PIPP were stably formed, and the effect of temperature on the stability of the emulsions was characterized. CNC-g-PIPP exhibited function as an effective particulate emulsifier at 4 °C because of the strong adsorption at the oil-water interface. However, the emulsions rapidly disintegrated at 45 °C, which is above the low critical solution temperature of PIPP on CNC, as the hydrophobized CNC-g-PIPP desorbed from the oil-water interface. Based on these findings, a thermally induced reversible emulsification/demulsification was presented. The resulting switchable particle-stabilized emulsion based on CNC-g-PIPP shows promise for the ability to control the stability of an emulsion in response to temperature, which is attractive for use in biological applications.

Multi-stimuli responsive poly(amidoamine) dendrimers with peripheral N-dialkylaminoethyl carbamate moieties

A novel type of multi-stimuli responsive dendrimer with thermo-, pH-, and CO₂-responsiveness was developed through facile modification of polyamidoamine dendrimers with various N-dialkylaminoethyl carbamate moieties.

Nanoscopic hydrophilic/hydrophilic phase-separation well below the LCST of polyphosphoesters

The complex phase separation process of thermoresponsive polyphosphoesters (PPEs) with an identical side-group structure but different copolymer compositions is characterized by electron paramagnetic resonance (EPR) spectroscopy.

Crystalline CO2 -Based Aliphatic Polycarbonates with Long Alkyl Chains

Carbon dioxide (CO₂ ) is an easily available, renewable carbon source and can be utilized as a comonomer in the catalytic ring-opening polymerization of epoxides to generate aliphatic polycarbonates. Dodecyl glycidyl ether (DDGE) is copolymerized with CO₂ and propylene oxide (PO) to obtain aliphatic poly(dodecyl glycidyl ether carbonate) and poly(propylene carbonate-co-dodecyl glycidyl ether carbonate) copolymers, respectively. The polymerization proceeds at 30 °C and high CO₂ pressure utilizing the established binary catalytic system (R,R)-Co(salen)Cl/[PPN]Cl. The copolymers with varying DDGE:PO ratios are characterized via NMR, FT-IR spectroscopy, and SEC, exhibiting high molecular weights between 11 400 and 37 900 g mol^-1 with dispersities (Р= M _w /M _n ) in the range of 1.37-1.61. Copolymers with T _g s of -11 °C or T _m s from 5 to 15 °C and thermal decomposition >200 °C depending on the comonomer ratio, are obtained as determined by differential scanning calorimetry/TGA.

Acid-Triggered Polymer Backbone Degradation and Disassembly to Achieve Release of Camptothecin from Functional Polyphosphoramidate Nanoparticles

Camptothecin (CPT) is a promising anticancer drug, yet its therapeutic potential has been limited by poor water solubility and facile hydrolysis of the lactone form into an inactive carboxylate form at neutral pH. In this work, a fundamental synthetic methodology was advanced to allow for the preparation of well-defined functional polyphosphoramidate (PPA)-based block copolymers that coassembled with CPT into nanoparticles, which underwent coincident acid-triggered polymer backbone degradation, nanoparticle disassembly, and CPT release. Encapsulation of CPT by the PPA polymer inhibited premature hydrolysis of CPT at pH 7.4 and enabled accelerated CPT release at pH 5.0 (ca. 4× faster than at pH 7.4). Two degradable oxazaphospholidine monomers, with one carrying an alkyne group, were synthesized to access well-defined block PPAs (dispersity, Đ<1.2) via sequential organobase-catalyzed ring-opening polymerizations (ROP). The resulting amphiphilic block copolymers (PEOMP-b-PBYOMP) were physically loaded with CPT to achieve well-dispersed nanotherapeutics, which allowed the aqueous suspension of CPT at concentrations up to 3.2 mg/mL, significantly exceeding the aqueous solubility of the drug (<2.0 μg/mL at 37 °C). Cytotoxicity studies revealed enhanced efficacy of the CPT-loaded nanoparticles over free CPT in cancer cells and similar toxicity in normal cells.