Enhanced Adsorption Stability and Biofunction Durability with Phosphonate-Grafted, PEGylated Copolymer on Hydroxyapatite Surface

Nonfouling surfaces are crucial in applications such as biosensors, medical implants, marine coatings, and drug delivery vehicles. However, their long-term coating stability and robust surface binding strength in physiological media remain challenging. Herein, a phosphonate-grafted, PEGylated copolymer on the hydroxyapatite (HA) surface is proposed to significantly improve the adsorption stability and thus enhance the biofunction durability accordingly. The phosphoryl (−PO3) grafted branch is employed in the functional polymer to facilitate attaching to the HA substrate. In addition, the polymer integrates the nonfouling polymer brushes of poly­(ethylene glycol) (PEG) with the cell-adhesive moiety of cyclic Arg-Gly-Asp-d-Phe-Cys peptides (cRGD). A systematic study on the as-synthesized PEGylated graft copolymer indicates a synergistic binding mechanism of the NH2 and PO3 groups to HA, achieving a high surface coverage with desirable adsorption stability. The cRGD/PEGylated copolymers of optimized grafting architecture are proven to effectively adsorb to HA surfaces as a self-assembled copolymer monolayer, showing stability with minimal desorption even in a complex, physiological medium and effectively preventing nonspecific protein adsorption as examined with X-ray photoelectron spectroscopy (XPS) and a quartz crystal microbalance with dissipation (QCM-D). Direct adhesion assays further confirm that the enhanced coating stability and biofunction durability of the phosphonate-grafted, cRGD-PEGylated copolymer can considerably promote osteoblast attachment on HA surfaces, meanwhile preventing microbial adhesion. This research has resulted in a solution of self-assembly polymer structure optimization that exhibits stable nonfouling characteristics

Template-Stripped, Ultraflat Gold Surfaces with Coplanar, Embedded Titanium Micropatterns

Ultraflat gold surfaces with coplanar, embedded titanium micropatterns, exhibiting extremely low roughness over the entire surface, have been obtained by a modified template-stripping procedure. Titanium is deposited onto photolithographically predefined regions of a silicon template. Following photoresist lift-off, the entire surface is backfilled with gold, template stripping is conducted, and an ultraflat micropatterned surface is revealed. Atomic force microscopy confirms a roughness of <0.5 nm RMS on both Ti and Au regions, with a topographically indistinguishable gold–titanium interface. Detailed surface-chemical maps of the patterned surfaces have been obtained by means of imaging X-ray photoelectron spectroscopy (<i>i-</i>XPS) as well as time-of-flight secondary-ion mass spectrometry (ToF-SIMS). They confirm the presence of well-separated Ti and Au regions, with a chemical contrast that is sharp (as determined by ToF-SIMS) and complete (as determined by <i>i</i>-XPS) across the Ti–Au interface. Thus, a surface has been fabricated that is physically homogeneous down to the nanoscale incorporating chemically distinct micropatterns consisting of two different metals, with totally contrasting surface chemistries

Facile Preparation of Poly(lactic acid)/Brushite Bilayer Coating on Biodegradable Magnesium Alloys with Multiple Functionalities for Orthopedic Application

Recently magnesium and its alloys have been proposed as a promising next generation orthopedic implant material, whereas the poor corrosion behavior, potential cytotoxicity, and the lack of efficient drug delivery system have limited its further clinical application, especially for the local treatment of infections or musculoskeletal disorders and diseases. In this study, we designed and developed a multifunctional bilayer composite coating of poly­(lactic acid)/brushite with high interfacial bonding strength on a Mg–Nd–Zn–Zr alloy, aiming to improve the biocorrosion resistance and biocompatibility of the magnesium-based substrate, as well as to further incorporate the biofunctionality of localized drug delivery. The composite coating consisted of an inner layer of poly­(lactic acid) serving as a drug carrier and an outer layer composed of brushite generated through chemical solution deposition, where a facile pretreatment of UV irradiation was applied to the poly­(lactic acid) coating to facilitate the heterogeneous nucleation of brushite. The in vitro degradation results of electrochemical measurements and immersion tests indicated a considerable reduction of magnesium degradation provided the composite coating. A systematic investigation of cellular response with cell viability, adhesion, and ALP assays confirmed the coated Mg alloy induced no toxicity to MC3T3-E1 osteoblastic cells but rather fostered cell attachment and proliferation and promoted osteogenic differentiation, revealing excellent biosafety and biocompatibility and enhanced osteoinductive potential. An in vitro drug release profile of paclitaxel from the composite coating was monitored with UV–vis spectroscopy, showing an alleviated initial burst release and a sustained and controlled release feature of the drug-loaded composite coating. These findings suggested that the bilayer poly­(lactic acid)/brushite coating provided effective protection for Mg alloy, greatly enhanced cytocompatibility and bioactivity, and, moreover, possessed local drug delivery capability; hence magnesium alloy with poly­(lactic acid)/brushite coating presents great potential in orthopedic clinical applications, especially for localized bone therapy

Reaction of Porous Silicon with Both End-Functionalized Organic Compounds Bearing α-Bromo and ω-Carboxy Groups for Immobilization of Biomolecules

Both end-functionalized (α-bromo and ω-carboxy) compounds were first tested for the radical reaction on the silicon−hydride (Si−H) terminated porous silicon (PSi) with/without the presence of diacyl peroxide initiator under microwave irradiation. Then the carboxylic acid monolayers (CAMs) assembled on PSi through the robust Si−C bonds were converted to amino-reactive linker, N-hydroxysuccinimide (NHS)-ester, terminated monolayers. And finally two proteins of bovine serum albumin (BSA) and lysozyme (Lys) were immobilized through amide bonds. The optimum PSi membrane for protein immobilization without collapse, with parameters of porous radii 4−10 nm and depth 0.2−4.6 μm, was prepared from the (100)-oriented p-type silicon wafer. The chemically converted surface products were monitored with Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM)

Diffusion of Hydrosilanes from the Control Layer to the Vinylsilane-Rich Flow Membrane during the Fabrication of Microfluidic Chips

During the fabrication of poly(dimethylsiloxane) (PDMS)-based microfluidic chips, polymethylhydrosiloxane (PMHS) species in the control layer diffuse into the flow membrane, which contains polymethylvinylsiloxane (PMVS), and the components cross-link together to form the mechanically enhanced membrane. The diffusion course was investigated by using attenuated total reflectance FTIR and the improvement of mechanical properties of the flow membrane was studied by measuring the Young's modulus and the tensile strength