Effects of Melanin on Optical Behavior of Polymer: From Natural Pigment to Materials Applications.

Melanin is a kind of ubiquitous natural pigment, which serves a variety of protective functions in many organisms. In the present study, natural melanin and synthetic melanin nanoparticles (NPs) were systematically investigated for its potential application in polymeric optical materials. A significant short-wavelength shielding and high visible light transparency polymer nanocomposite was easily obtained via tuning the melanin particle size. In particular, the nanocomposite film with melanin NPs (diameter ≈ 15 nm) loading even as low as 1 wt % blocks most ultraviolet light below 340 nm and still keeps high visible light transparency (83%) in the visible spectrum. More importantly, because of the excellent photoprotection and radical scavenging capabilities of melanin, the resulting polymer nanocomposite exhibits outstanding photostability. In effect, such fantastic melanin NPs is promising for applications in various optical materials.

[Phage display peptide library for screening the peptides that specifically bind to osteoblasts cells].

OBJECTIVE: To explore the experimental methods that the phage peptide library technology screening human osteoblast specificity polypeptide, which will provide the basis of the experiment of the Ti surface biolization modification. METHODS: Human calvarial osteoblasts were used as the target cells for whole-cell biopanning from a 12-mer peptide phage-display library. Cell eluent and cell lysis buffer were cultivate and count respectively after washing. Then the target cells were analyzed by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence detection to authenticate the positive phage clones by human gingival fibroblast as the absorber cells. The positive phage clones were deduced by DNA sequencing. RESULTS: After four rounds of screening, twenty-two positive phage clones were found out from randomly selected phage monoclonals, whose single-strand DNA were extracted and sequenced. Amino acid sequence of the highest frequency peptide was MGWSWWPETWPM. CONCLUSIONS: The specific peptide against human osteoblasts can be obtained from a phage-display peptide library for use as a new research approach and experimental basis of the biolization modification of the titanium surface.

Self-assembly of various Au nanocrystals on functionalized water-stable PVA/PEI nanofibers: a highly efficient surface-enhanced Raman scattering substrates with high density of "hot" spots.

We have demonstrated a facile approach for the fabrication of flexible and reliable sulfydryl functionalized PVA/PEI nanofibers with excellent water stability for the self-assembly of Au nanocrystals, such as Au nanoparticles (AuNPs), Au nanoflowers (AuNFs) and Au nanorods (AuNRs), used as the highly efficient surface-enhanced Raman scattering (SERS) substrates for the detection of rhodamine B (RhB). Various methods were employed to cross-link the PVA nanofibers with better morphology and porous structures after immersing in water for desired times. Various SERS-active Au nanocrystals, such as AuNPs, AuNFs, and AuNRs have been successfully synthesized. After the grafting of MPTES on the cross-linked PVA/PEI nanofibers, the Au nanocrystals can easily be self-assembled on the surfaces of the nanofibers because of the strong interactions of the Au-S chemical bondings. The Au nanocrystals self-assembled throughout the PVA/PEI nanofibers used as SERS substrates all exhibit enhanced SERS signals of RhB compared with their individual nanocrystals. It is mainly due to the close interparticle distance, mutual orientation and high density of "hot" spots, that can strongly affect the overall optical response and the SERS enhancement. By changing the amounts of the self-assembled AuNFs on the nanofibers, we can control the density of the "hot" spots. With the increased amounts of the AuNFs throughout the nanofibers, the SERS substrates show enhanced Raman signals of the RhB, indicating that the increased density of "hot" spots can directly lead to the SERS enhancement. The AuNFs/(PVA/PEI) SERS substrates show good sensitivity, reliability and low detection limit (10(-9) M). The presented approach can be broadly applicable to the assembly of different types of plasmonic nanostructures and these novel materials with strong SERS enhancement can be applied in bioanalysis and biosensors.

Use of TX100-dangled epoxy as a reactive noncovalent dispersant of vapor-grown carbon nanofibers in an aqueous solution.

The dispersion of carbon nanotubes (CNTs) into individual particles or small bundles has remained a vexing problem that limits the use of the excellent properties of CNTs in composite applications. Noncovalent functionalization is an attractive option for changing the interfacial properties of nanotubes because it does not destroy the nanotube grapheme structure. In this study, a new reactive copolymer, epoxy-toluene diisocyanate-Triton X-100 (EP-TDI-TX100) was successfully synthesized, which is shown to be highly effective in dispersing vapor-grown carbon nanofibers (VGCNFs) into individual or small bundles, as evidenced by transmission electron microscopy (TEM) and UV-vis absorption spectra. The strong π-π interaction between VGCNFs and EP-TDI-TX100 was revealed by Raman spectra and the covalent reaction between curing agent was confirmed via Fourier transform infrared spectroscopy. For an effective dispersion, the optimum weight ratio of EP-TDI-TX100 to VGCNFs is 2:1. The maximum VGCNF concentration that can be homogeneously dispersed in an aqueous solution is approximately 0.64 mg/mL. The EP-TDI-TX100 molecules are adsorbed on the VGCNF surface and prevent reaggregation of VGCNFs, so that a colloidal stability of VGCNF dispersion can be maintained for 6 months.

Facile fabrication of AgNPs/(PVA/PEI) nanofibers: high electrochemical efficiency and durability for biosensors.

A novel, facile and green approach for the fabrication of H2O2, glutathione (GSH) and glucose detection biosensor using water-stable PVA and PVA/PEI nanofibers decorated with AgNPs by combining an in situ reduction approach and electrospinning technique has been demonstrated. Small, uniform and well-dispersed AgNPs embedded in the PVA nanofibers and immobilized on functionalized PVA/PEI nanofibers indicate the highly sensitive detection of H2O2 with a detection limit of 5 µM and exhibit a fast response, broad linear range, low detection limit and excellent stability and reusability.