Slippery Liquid-Attached Surface for Robust Biofouling Resistance.

Materials for biodevices and bioimplants commonly suffer from unwanted but unavoidable biofouling problems due to the nonspecific adhesion of proteins, cells, or bacteria. Chemical coating or physical strategies for reducing biofouling have been pursued, yet highly robust antibiofouling surfaces that can persistently resist contamination in biological environments are still lacking. In this study, we developed a facile method to fabricate a highly robust slippery and antibiofouling surface by conjugating a liquid-like polymer layer to a substrate. This slippery liquid-attached (SLA) surface was created via a one-step equilibration reaction by tethering methoxy-terminated polydimethylsiloxane (PDMS-OCH3) polymer brushes onto a substrate to form a transparent "liquid-like" layer. The SLA surface exhibited excellent sliding behaviors toward a wide range of liquids and small particles and antibiofouling properties against the long-term adhesion of small biomolecules, proteins, cells, and bacteria. Moreover, in contrast to superomniphobic surfaces and liquid-infused porous surfaces (SLIPS) requiring micro/nanostructures, the SLA layer could be obtained on smooth surfaces and maintain its biofouling resistance under abrasion with persistent stability. Our study offers a simple method to functionalize surfaces with robust slippery and antibiofouling properties, which is promising for potential applications including medical implants and biodevices.

Protection of Nanostructures-Integrated Microneedle Biosensor Using Dissolvable Polymer Coating.

Real-time transdermal biosensing provides a direct route to quantify biomarkers or physiological signals of local tissues. Although microneedles (MNs) present a mini-invasive transdermal technique, integration of MNs with advanced nanostructures to enhance sensing functionalities has rarely been achieved. This is largely due to the fact that nanostructures present on MNs surface could be easily destructed due to friction during skin insertion. In this work, we reported a dissolvable polymer-coating technique to protect nanostructures-integrated MNs from mechanical destruction during MNs insertion. After penetration into the skin, the polymer could readily dissolve by interstitial fluids so that the superficial nanostructures on MNs could be re-exposed for sensing purpose. To demonstrate this technique, metallic and resin MNs decorated with vertical ZnO nanowires (vNWs) were employed as an example. Dissolvable poly(vinyl pyrrolidone) was spray-coated on the vNW-MNs surface as a protective layer, which effectively protected the superficial ZnO NWs when MNs penetrated the skin. Transdermal biosensing of H2O2 biomarker in skin tissue using the polymer-protecting MNs sensor was demonstrated both ex vivo and in vivo. The results indicated that polymer coating successfully preserved the sensing functionalities of the MNs sensor after inserting into the skin, whereas the sensitivity of the MN sensor without a coating protection was significantly compromised by 3-folds. This work provided unique opportunities of protecting functional nanomodulus on MNs surface for minimally invasive transdermal biosensing.