Peptidic inhibition of the enzyme tyrosinase, responsible for skin pigmentation and food browning, would be extremely useful for the food, cosmetics, and pharmaceutical industries. In order to identify novel inhibitory peptides, a library of short sequence oligopeptides was screened to reveal direct interaction with the tyrosinase. A phage displaying heptapeptide (IQSPHFF) was found to bind most strongly to tyrosinase. The inhibitory activity of the heptapeptide was evaluated using mushroom tyrosinase. The results showed that the peptide inhibited both the monophenolase and diphenolase activities of mushroom tyrosinase with IC50 values of 1.7 and 4.0 mM, respectively. The heptapeptide is thought to be a reversible competitive inhibitor of diphenolase with the inhibition constants (Ki) of 0.765 mM. To further investigate how the heptapeptide exerts its inhibitory effect, a docking study between tyrosinase and heptapeptide was performed. The simulation showed that the heptapeptide binds in the active site of the enzyme near the catalytically active Cu ions and forms hydrogen bonds with five histidine residues on the active site. Phage display technology is thus a useful approach for the screening of potential tyrosinase inhibitors and could be widely applicable to a much wider range of enzymes.

The self-assembly of a heptapeptide and phosphotungstic acid into hollow spheres with pH-responsive properties was successfully achieved using a template-free method. The release of the model drug doxorubicin from these spheres was found to be highly pH sensitive, giving them great potential for targeted drug delivery.

•A series of copolymers with different various molecular weights were synthesized.•Novel thermo-sensitive and biocompatible electrospun nanofibers were fabricated.•Effects of hydrophilicity/hydrophobicity of a drug on release were investigated.•The drug release mechanism from nanofibers was discussed.The thermo-sensitive copolymer poly(N-vinylcaprolactam-co-methacrylic acid) (PNVCL-co-MAA) was synthesized by free radical polymerization and the resulting nanofibers were fabricated using an electrospinning process. The molecular weight of the copolymer was adjusted by varying the content of methacrylic acid (MAA) while keeping that of N-vinylcaprolactam (NVCL) constant. Hydrophilic captopril and hydrophobic ketoprofen were used as model drugs, and PNVCL-co-MAA nanofibers were used as the drug carrier to investigate the effects of drug on its release properties from nanofibers at different temperatures. The results showed that slow release over several hours was observed at 40 °C (above the lower critical solution temperature (LCST) of PNVCL-co-MAA), while the drugs exhibited a burst release of several seconds at 20 °C (below the LCST). Drug release slowed with increasing content of the hydrophobic monomer NVCL. The hydrophilic captopril was released at a higher rate than the hydrophobic ketoprofen. The drug release characteristics were dependent on the temperature, the portion of hydrophilic groups and hydrophobic groups in the copolymer and hydrophilicity/hydrophobicity of drug. Study on the mechanism of release showed that Korsmeyer–Peppas model as a major drug release mechanism. Given these results, the PNVCL-co-MAA copolymers are proposed to have useful applications in intellectual drug delivery systems.

•A facile, time-saving approach to assemble Fomc-FF composite hydrogels was designed.•Hydrogel structures including nanowires, layered films and honeycombs can be controlled.•The role of SA in the Fmoc-FF/SA composite hydrogel was further clarified.Dipeptides and their derivatives have attracted tremendous attention owning to their excellent abilities of self-assemble assembling into various structures which have great potentials for applications in biology and/or nanotechnology. In the present study, we dedicate to fabricate a rigid and structure controllable Fmoc-FF/SA composite hydrogel. We found that the modified dipeptide, fluorenyl-9-methoxycarbonyl (Fmoc)-diphenylalanine (Phe-Phe) can self-assemble into rigid hydrogels with structures of nanowires, layered thin films or honeycombs as the change of sodium alginate (SA) concentration. Meanwhile, CD-spectroscopy demonstrated that SA appeared to control the process, but it did not change the arrangement of the Fmoc-FF peptide. Our results demonstrated that the formed hydrogel showed physical and chemical stability as well as possessing good biocompatibility. Rheological measurements showed that the addition of SA could improve the stability of the hydrogel. Cell viability assay revealed that the Fmoc-FF and Fmoc-FF/SA hydrogels are both beneficial for cell proliferation in-vitro. Our results indicated that the fabricated Fmoc-FF/SA composite hydrogels could be used in tissue engineering and drug delivery in the future.

•A novel fluorescent biomimetic sensor based on MWCNT-QDs was designed.•The sensor exhibited a fast mass-transfer speed with a response time of 25 min.•The sensor possessed a highly selective recognition to BSA.A novel molecularly imprinted optosensing material based on multi-walled carbon nanotube-quantum dots (MWCNT-QDs) has been designed and synthesized for its high selectivity, sensitivity and specificity in the recognition of a target protein bovine serum albumin (BSA). Molecularly imprinted polymer coated MWCNT-QDs using BSA as the template (BMIP-coated MWCNT-QDs) exhibits a fast mass-transfer speed with a response time of 25 min. It is found that the BSA as a target protein can significantly quench the luminescence of BMIP-coated MWCNT-QDs in a concentration-dependent manner that is best described by a Stern–Volmer equation. The KSV for BSA is much higher than bovine hemoglobin and lysozyme, implying a highly selective recognition of the BMIP-coated MWCNT-QDs to BSA. Under optimal conditions, the relative fluorescence intensity of BMIP-coated MWCNT-QDs decreases linearly with the increasing target protein BSA in the concentration range of 5.0 × 10−7–35.0 × 10−7 M with a detection limit of 80 nM.

•MWCNTs-COOH/PVA nanofiber mats were fabricated using electrospinning.•A transparent and conductive film was generated by self-assembly when the nanofiber mats were immersed in water.•The mechanical properties, electrical conduction and optical transparency of the composite films were studied.•The potential mechanisms governing the transparent conductive composite films from nanofiber mats were raised.Carboxylated multi-walled carbon nanotubes (MWCNTs-COOH)/poly(vinyl alcohol) (PVA) nanofiber mats were fabricated using electrospinning. Due to the hydrophilic and swelling properties of the nanofibers, a transparent film was generated by self-assembly when the nanofibers were immersed in water. The composite film with MWCNTs-COOH fraction 8.76 wt% exhibits electrical conductivity of 1.8×10−4 S/cm, while maintaining 166.98 MPa tensile strength and 61% optical transmittance. The method reported here is simple and feasible for large scale production of CNTs based composite films.

Composite non-woven mats of poly(vinyl pyrrolidone) (PVP), chitosan, and Fe3O4 were successfully fabricated using coaxial-electrospinning technique with PVP/chitosan as the shell and PVP/Fe3O4 as the core. Because of the templating and confinement properties of the nanofibers, magnetic chitosan nanoparticles (MCNPs) could be spontaneously formed through molecular self-assembly when the composite fibers were dissolved on treatment with acetum solution. By changing the weight ratio of Fe3O4:chitosan, the size of the MCNPs could be varied. The morphology, chemical composition, and magnetic characteristics of composite particles were characterized by means of scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. Experimental results indicated that the composite particles were super-paramagnetic with sizes in the range of 15–40 nm. This facile and new synthesis route comprises a convenient strategy to generate composite particles and should be broadly applicable to a wide range of systems, serving as a platform for the facile development of novel composite materials.

In this paper, the liquid–liquid–solid triple-phase data of some aqueous two-phase systems (ATPSs) containing hydrophilic organic solvents (HOS) and simple salts were explored. The systems studied comprise aqueous solutions containing ethanol, 1-propanol, 2-propanol, or acetone with (NH4)2SO4 and solutions containing 1-propanol with (NH4)2SO4, NaCl, or KCl. The Gibbs phase rule predicts that there is a linear relationship existing at such a triple-phase boundary. The linear liquid–liquid–solid boundaries were determined, and the effects of temperature, solvent, and salt on the boundary were investigated. The tie line length (TLL) of the systems distributed on the triple-phase boundary was invariant. Phase equilibrium experiments determined that the average TLL of ethanol–(NH4)2SO4 ATPSs at 298.15 K was 62.93 % with a standard deviation of 2.13 %. The linear liquid–liquid–solid triple-phase boundary was used to elucidate the two-phase region and determine the content of organic solvent or salt in an unknown sample. These results increase our understanding of HOS–salt–water aqueous two phase system (ATPS) and will be useful for those looking to develop new systems for separation science.

Thermosensitive core–shell magnetic composite particles with a magnetic silica core and a rich poly (N-vinylcaprolactam) (PNVCL) shell layer were developed for studying the adsorption of bovine serum albumin (BSA) in a batch system. Various analytical and spectroscopic techniques including SEM, FT-IR, VSM and DSC were used to characterize the adsorbents prepared in this study. The combined effects of operating parameters such as initial temperature, pH and initial BSA concentration on the adsorption were analyzed using response surface methodology. The optimum conditions were 40 °C, pH 4.68, and initial BSA concentration 2.0 mg/mL. Desorption experiments were conducted by altering the system temperature where a high recovery rate of protein was obtained. The separation process developed here indicates that the dual-responsive smart adsorbent could be an ideal candidate for the separation of protein.Graphical abstractResearch highlights► A simple method for the fabrication of a smart material with a γ-Fe2O3/SiO2 core and thermosensitive poly (N-vinylcaprolactam) (PNVCL) shell was developed. ► The LCST of poly (N-vinylcaprolactam) was not significantly changed after encapsulating the γ-Fe2O3/SiO2 core. ► Response surface methodology (RSM) analysis showed that temperature and initial BSA concentration were the main factors that affected the adsorption capacity. ► The desorption process revealed that temperature played an important role in protein recovery.

This investigation, in vitro, shows that ozagrel, an antithrombotic drug, inhibited both monophenolase and diphenolase activities of mushroom tyrosinase when l-tyrosine and l-DOPA were assayed spectrophotometrically, respectively. The IC50 values, for monophenolase and diphenolase activities, were 1.35 and 3.45 mM, respectively. Ozagrel was estimated to be a reversible mixed-type inhibitor of diphenolase activity with the constants (KS1, KS2, Ki1, and Ki2) determined to be 2.21, 3.89, 0.454, and 0.799 mM, repectively. Increasing ozagrel concentrations provoked longer lag periods as well as a concomitant decrease in the monophenolase activity. Inhibition experiment demonstrated that ozagrel bound the enzyme at a site distincted from the substrate active site, but it bound to either E (Enzyme) or ES (Enzyme-Substrate) complex.

The self-assembly of a heptapeptide and phosphotungstic acid into hollow spheres with pH-responsive properties was successfully achieved using a template-free method. The release of the model drug doxorubicin from these spheres was found to be highly pH sensitive, giving them great potential for targeted drug delivery.