Biocompatibility and Physiological Thiolytic Degradability of Radically Made Thioester-Functional Copolymers: Opportunities for Drug Release

Being nondegradable, vinyl polymers have limited biomedical applicability. Unfortunately, backbone esters incorporated through conventional radical ring-opening methods do not undergo appreciable abiotic hydrolysis under physiologically relevant conditions. Here, PEG acrylate and di(ethylene glycol) acrylamide-based copolymers containing backbone thioesters were prepared through the radical ring-opening copolymerization of the thionolactone dibenzo[c,e]oxepin-5(7H)-thione. The thioesters degraded fully in the presence of 10 mM cysteine at pH 7.4, with the mechanism presumed to involve an irreversible S-N switch. Degradations with N-acetylcysteine and glutathione were reversible through the thiol-thioester exchange polycondensation of R-SC(═O)-polymer-SH fragments with full degradation relying on an increased thiolate/thioester ratio. Treatment with 10 mM glutathione at pH 7.2 (mimicking intracellular conditions) triggered an insoluble-soluble switch of a temperature-responsive copolymer at 37 °C and the release of encapsulated Nile Red (as a drug model) from core-degradable diblock copolymer micelles. Copolymers and their cysteinolytic degradation products were found to be noncytotoxic, making thioester backbone-functional polymers promising for drug delivery applications.

Radical ring-opening polymerization of novel azlactone-functionalized vinyl cyclopropanes

Synthesis of new azlactone-functionalized vinyl cyclopropane monomers, corresponding (co)polymers and their reactivity with an amine compound.

Transport-Limited Adsorption of Plasma Proteins on Bimodal Amphiphilic Polymer Co-Networks: Real-Time Studies by Spectroscopic Ellipsometry

Traditional hydrogels are commonly limited by poor mechanical properties and low oxygen permeability. Bimodal amphiphilic co-networks (β-APCNs) are a new class of materials that can overcome these limitations by combining hydrophilic and hydrophobic polymer chains within a network of co-continuous morphology. Applications that can benefit from these improved properties include therapeutic contact lenses, enzymatic catalysis supports, and immunoisolation membranes. The continuous hydrophobic phase could potentially increase the adsorption of plasma proteins in blood-contacting medical applications and compromise in vivo material performance, so it is critical to understand the surface characteristics of β-APCNs and adsorption of plasma proteins on β-APCNs. From real-time spectroscopic visible (Vis) ellipsometry measurements, plasma protein adsorption on β-APCNs is shown to be transport-limited. The adsorption of proteins on the β-APCNs is a multistep process with adsorption to the hydrophilic surface initially, followed by diffusion into the material to the internal hydrophilic/hydrophobic interfaces. Increasing the cross-linking of the PDMS phase reduced the protein intake by limiting the transport of large proteins. Moreover, the internalization of the proteins is confirmed by the difference between the surface-adsorbed protein layer determined from XPS and bulk thickness change from Vis ellipsometry, which can differ up to 20-fold. Desorption kinetics depend on the adsorption history with rapid desorption for slow adsorption rates (i.e., slow-diffusing proteins within the network), whereas proteins with fast adsorption kinetics do not readily desorb. This behavior can be directly related to the ability of the protein to spread or reorient, which affects the binding energy required to bind to the internal hydrophobic interfaces.

Double-networks based on pH-responsive, amphiphilic “core-first” star first polymer conetworks prepared by sequential RAFT polymerization

Double-networks based on amphiphilic polymer conetworks synthesized using RAFT polymerization were prepared, exhibiting pH-responsiveness, nanophase separation and enhanced mechanical properties.

Poly(N-vinylimidazole)-l-poly(propylene glycol) amphiphilic conetworks and gels: molecularly forced blends of incompatible polymers with single glass transition temperatures of unusual dependence on the composition

New molecularly forced blends of incompatible poly(N-vinylimidazole) and poly(propylene glycol) polymers with single glass transition temperatures.

Disulfide bonds-containing amphiphilic conetworks with tunable reductive-cleavage

The disulfide bonds-containing amphiphilic conetworks were presented with tunable reduction-cleavage via click reaction of azide terminated poly(ε-caprolactone) and alkyne-terminated polyethylene glycol.