The orientation of antibodies on surfaces is critical to the performance of biosensors. Due to the charge distribution within an antibody molecule, it is hoped that the orientation of adsorbed antibodies can be controlled by adjusting microenvironments (e.g., surface and solution properties). In this work, we investigated the orientations of two types of monoclonal anti-human chorionic gonadotropin (anti-hCG) adsorbed on NH2 (positively charged) and COOH (negatively charged) terminated self-assembled monolayers (SAMs) by surface plasmon resonance (SPR) biosensors. Adsorbed antibody molecules on surfaces were also characterized by atomic force microscopy. Results show that the orientation of the IgG1 type antibody is better on the NH2 surface than on the COOH surface, as indicated by a higher hCG to adsorbed anti-hCG ratio on the NH2 surface from SPR experiments. However, for the IgG2a type antibody, the antigen-to-antibody ratio, and thus the orientation of the adsorbed IgG2a, is similar on the NH2- and COOH-terminated SAM surfaces. Surface charge affects the orientation of IgG2a less than IgG1 due to the smaller dipole moment of IgG2a compared to IgG1. This work provides not only a fundamental understanding of how microenvironments affect protein behavior on surfaces but also a useful guide to designing surfaces for applications, such as biosensors and biomaterials.

Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) has been well studied for its superhydrophilic and ultralow biofouling properties, making it a promising material for superabsorbent and nonadherent wound dressings. Electrospinning provides multiple desirable features for wound dressings, including high absorptivity due to high surface-area-to-volume ratio, high gas permeation, and conformability to contour of the wound bed. The goal of this work is to develop a fibrous membrane of PSBMA via electrospinning and evaluate its properties related to wound dressing applications. Being superhydrophilic, PSBMA fibers fabricated by a conventional electrospinning method would readily dissolve in water, whereas if cross-linker is added, the formation of hydrogel would prevent electrospinning. A three-step polymerization-electrospinning-photo-cross-linking process was developed in this work to fabricate the cross-linked electrospun PSBMA fibrous membrane. Such electrospun membrane was stable in water and exhibited high water absorption of 353% (w/w), whereas the PSBMA hydrogel only absorbed 81% water. The electrospun membrane showed strong resistance to protein adsorption and cell attachment. Bacterial adhesion studies using Gram negative P. aeruginosa and Gram positive S. epidermidis showed that the PSBMA electrospun membrane was also highly resistant to bacterial adhesion. The Ag(+)-impregnated electrospun PSBMA membrane was shown microbicidal, against both S. epidermidis and P. aeruginosa. Such electrospun PSBMA membrane is ideal for a novel type of nonadherent, superabsorbent, and antimicrobial wound dressing. The superior water absorption aids in fluid removal from highly exudating wounds while keeping the wound hydrated to support healing. Because of the resistance to protein, cell, and bacterial adhesion, the dressing removal will neither cause patients' pain nor disturb the newly formed tissues. The dressing also prevents the attachment of environmental bacteria and offers broad-spectrum antimicrobial activity. It is the first work to develop the water-stable electrospun PSBMA membrane, which has great potential for wound dressing and other applications.

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We propose a design of an extremely broad frequency band absorber based on destructive interference mechanism. Metamaterial of multilayered SRRs structure is used to realize a desirable refractive index dispersion spectrum, which can induce a successive anti-reflection in a wide frequency range. The corresponding high absorptance originates from the destructive interference of two reflection waves from the two surfaces of the metamaterial. A strongly absorptive bandwidth of almost 60 GHz is demonstrated in the range of 0 to 70 GHz numerically. This design provides an effective and feasible way to construct broad band absorber in stealth technology, as well as the enhanced transmittance devices.

A serine-based zwitterionic poly(serine methacrylate) (pSerMA) was developed in this work to be used as a potential antifouling material. A surface-initiated photoiniferter-mediated polymerization (SI-PIMP) method was used to graft polymer brushes on gold surfaces. The pSerMA-grafted samples with different polymer film thicknesses were readily prepared by varying the UV-irradiation time. With the optimal film thickness, the adsorptions from bovine serum albumin, human serum, and human plasma onto the pSerMA-grafted surfaces, as evaluated by a surface plasmon resonance (SPR) biosensor, were 1.8, 9.2, and 12.9 ng/cm(2), respectively, comparable to the traditional antifouling material such as poly(ethylene glycol). The pSerMA-grafted surfaces also strongly resisted adhesion from bovine aortic endothelial cells. This is the first work to develop an amino acid-based zwitterionic polymer as an antifouling material, demonstrating that pSerMA is a promising alternative to the traditional ethylene glycol-based antifouling materials.