Microparticles for Drug Delivery Based on Functional Polycaprolactones with Enhanced Degradability: Loading of Hydrophilic and Hydrophobic Active Compounds

Fabricating functional circuits on 3D freeform surfaces via intense pulsed light-induced zinc mass transfer

Deployment of functional circuits on a 3D freeform surface is of significant interest to wearable devices on curvilinear skin/tissue surfaces or smart Internet-of-Things with sensors on 3D objects. Here we present a new fabrication strategy that can directly print functional circuits either transient or long-lasting onto freeform surfaces by intense pulsed light-induced mass transfer of zinc nanoparticles (Zn NPs). The intense pulsed light can locally raise the temperature of Zn NPs to cause evaporation. Lamination of a kirigami-patterned soft semi-transparent polymer film with Zn NPs conforming to a 3D surface results in condensation of Zn NPs to form conductive yet degradable Zn patterns onto a 3D freeform surface for constructing transient electronics. Immersing the Zn patterns into a copper sulfate or silver nitrate solution can further convert the transient device to a long-lasting device with copper or silver. Functional circuits with integrated sensors and a wireless communication component on 3D glass beakers and seashells with complex surface geometries demonstrate the viability of this manufacturing strategy.

Functional biodegradable polymers via ring-opening polymerization of monomers without protective groups

Biodegradable polymers are of current interest and chemical functionality in such materials is often demanded in advanced biomedical applications. Functional groups often are not tolerated in the polymerization process of ring-opening polymerization (ROP) and therefore protective groups need to be applied. Advantageously, several orthogonally reactive functions are available, which do not demand protection during ROP. We give an insight into available, orthogonally reactive cyclic monomers and the corresponding functional synthetic and biodegradable polymers, obtained from ROP. Functionalities in the monomer are reviewed, which are tolerated by ROP without further protection and allow further post-modification of the corresponding chemically functional polymers after polymerization. Synthetic concepts to these monomers are summarized in detail, preferably using precursor molecules. Post-modification strategies for the reported functionalities are presented and selected applications highlighted.

Polyglycidol-based metal adhesion promoters

Hydrophilic adhesion promoters that facilitate intimate binding between metals and polymers are an important class of materials with a wide variety of applications in biomedical coatings. Currently, non-poly(meth-)acrylate based hydrophilic polymeric adhesives are unavailable. Here, we report the preparation of such adhesion-promoters based on linear polyglycidol for biomedical applications. The adhesion promoting polymer is prepared from partly phosphonoethylated polyglycidol in three steps. First, the remaining hydroxyl groups of the polyglycidol backbone are reacted with acryloyl chloride; secondly, the phosphonate groups are chemoselectively dealkylated using bromotrimethylsilane. Finally, the bis(trimethylsilyl)phosphonate intermediate is converted to the phosphonic acid through ethanolysis. The reaction conditions of each synthetic step are optimized individually and the products are characterized by ¹H, ³¹P NMR and SEC analysis. The optimized reaction conditions are applied to establish a straightforward one-pot reaction, resulting in an ethanolic formulation of the adhesion promoter, which can be used immediately for the coating application. Special attention is paid to the stability of the intermediates, the chemoselectivity of the reactions and the shelf-life of the product. ¹H NMR spectroscopy reveals hydrolytic instability of the product under ambient conditions; however, the polymers are sufficiently stable in dry ethanol for at least 14 days. The combination of this hydrophilic polymer with acrylate and phosphonic acid groups constitutes a versatile platform technology for the preparation of thin primer coatings on metal substrates for biomedical applications. The phosphonic acid residues assure strong binding to stainless steel wires and the acrylates can be addressed by UV light to enable crosslinking, thus improving mechanical stability and adhesion between the substrate and a biomedical hydrogel coating. The quality of the adhesion promotion to stainless steel wires is verified by using a lubricious, hydrogel top coat and by evaluating friction and wear resistance of this total coating system. Constant values for friction and wear are obtained, proving the applicability of phosphonic acid-functionalized polyglycidols as metal adhesion promoters for biomedical applications.

Dual delivery of chlorhexidine and platelet-derived growth factor-BB for enhanced wound healing and infection control

Wound treatment can require molecules that both enhance healing and control infection. As in many biomedical applications, the options for therapeutic molecules may include both hydrophilic and hydrophobic molecules. The goal of this study was to investigate a polymer system for drug delivery that simultaneously delivers platelet-derived growth factor (PDGF)-BB, a hydrophilic protein known to promote wound healing, and chlorhexidine (CHX), a hydrophobic antimicrobial agent for infection treatment. Poly(lactic-co-glycolic acid) (PLGA) microspheres were prepared using different polymer formulations in a double emulsion process. CHX encapsulation efficiency was 19.6±0.8% and 28.9±1.5% for PLGA 50:50 and 85:15, respectively. The presence of CHX significantly increased PDGF-BB encapsulation efficiency relative to PDGF-BB alone. Both molecules could be released for up to 50 days and exhibited bioactivity for greater than 3 (PLGA 85:15) or 8 (PLGA 50:50) weeks using in vitro bacteria and cellular assays. An infected wound model was used to evaluate the system in vivo. Wounds treated with the dual delivery system showed decreased levels of infection and increased healing. Vascular analysis of wound tissues also showed higher levels of mature vasculature with the delivery of PDGF-BB. In conclusion, we have evaluated a drug delivery system for simultaneous delivery of hydrophobic and hydrophilic molecules and have shown that this system can improve healing and reduce bacteria levels in an infected wound model. This system could be applied to other therapeutic applications where sustained delivery of hydrophobic and hydrophilic molecules is required.