Yanan Sun

Nonenzymatic biosensor based on CuxO nanoparticles deposited on polypyrrole nanowires for improving detectionrange

Cu(x)O (CuO and Cu₂O composite) nanoparticles modified polypyrrole (PPy) nanowires were fabricated and used as a biosensor for detecting glucose (GLC). PPy nanowires were prepared through electrodeposition, while Cu(x)O nanoparticles were deposited on PPy nanowires by electrodeposition and electrochemical oxidation in situ. The scanning electron microscopy images showed the Cu(x)O nanoparticles aligned along the PPy nanowires uniformly and the average size of Cu(x)O nanoparticles is about 90 nm. The electrocatalytic activity of Cu(x)O/PPy/Au towards GLC was investigated under alkaline conditions using cyclic voltammetry and chronoamperometry. The sensor exhibited a linear range up to 8 mM of GLC, which is more than two times of most of the existing non-enzymatic GLC sensors based on CuO or Cu₂O. The sensitivity of the sensor is 232.22 μAmM⁻¹ cm⁻² and detection limit is 6.2 μM (at signal/noise=3). Moreover, the sensor showed excellent selectivity, reproducibility and stability properties. These excellent performances make Cu(x)O/PPy/Au a good nonenzymatic GLC sensor.

Microwave-assisted one-step rapid synthesis of folic acid modified gold nanoparticles for cancer cell targeting and detection

In this study, folic acid-protected gold nanoparticles (FA-GNPs) were fabricated by one-step reduction of HAuCl4 by folic acid under microwave irradiation. FA-GNPs were successfully used to target and detect human cervical carcinoma cells.

Polydopamine-functionalized nanographene oxide: a versatile nanocarrier for chemotherapy and photothermal therapy

For releasing both drug and heat to selected sites, a combination of chemotherapy and photothermal therapy in one system is a more effective way to destroy cancer cells than monotherapy. Graphene oxide (GO) with high drug-loading efficiency and near-infrared (NIR) absorbance has great potential in drug delivery and photothermal therapy, but it is difficult to load drugs with high solubility. Herein, we develop a versatile drug delivery nanoplatform based on GO for integrated chemotherapy and photothermal therapy by a facile method of simultaneous reduction and surface functionalization of GO with poly(dopamine) (PDA). Due to the excellent adhesion of PDA, both low and high solubility drugs can be encapsulated in the PDA-functionalized GO nanocomposite (rGO-PDA). The fabricated nanocomposite exhibits good biocompatibility, excellent photothermal performance, high drug loading capacity, an outstanding sustained release property, and efficient endocytosis. Moreover, NIR laser irradiation facilitates the release of loaded drugs from rGO-PDA. These features make the rGO-PDA nanocomposite achieve excellent in vivo synergistic antitumor therapeutic efficacy.

Peptide derived from Pvfp-1 as bioadhesive on bio-inert surface

Surface property is one important characteristic of materials, especially for ones that are bio-inert but designed for bio-medical application. In this study, we designed a series of peptides and compared their capacities as bioadhesive to improve the surface bioactivity of bio-inert material. The peptides were designed according to the sequence of Perna viridis foot protein 1 (Pvfp-1), one of the Mfp-1s (mussel foot protein 1) which play key roles in wet adhesion of mussel byssus. And the Teflon (PTFE) was chosen as a model of bio-inert material. With adsorption, adhesion and coating analysis, it was found that peptide C2 (M) (derived from the non-repeating region of Pvfp-1, contains modified DOPA) has superior coating and adhesion abilities especially on the bio-inert surface of PTFE. After coating with peptide C2 (M), the cell adhesion and spreading of osteoblast MC3T3-E1 cells on PTFE were significantly improved compared with those on non-coated surface, and the peptide-coating did not show any cell toxicity. Therefore, peptide C2 (M) is effective for improving the bioactivity of bio-inert PTFE, and could be potentially used as a bioadhesive on other bio-inert materials for biomedical application. Moreover, this study also provided new insights in designing other peptide-based bioadhesive materials.

Synthesis of polypyrrole nanowires with positive effect on MC3T3-E1 cell functions through electrical stimulation

Conducting polymer polypyrrole (PPy) possesses good biocompatibility and conductivity and has been used as functional coatings in bone tissue regeneration. In this study, a cholic acid doped PPy nanowires (PPy NWs) coating was electrochemically polymerized on the surface of titanium (Ti). The porous intertwined PPy NWs coating exhibited excellent electrical conductivity and electrochemical activity, better hydrophilicity and higher surface energy. In vitro cell experiments demonstrated that the PPy NWs coating together with a 10μA substrate-mediate electrical stimulation (ES) was capable to positive regulate the functions of MC3T3-E1 such as cell adhesion, proliferation and differentiation. Further long-term functions of cell tests including alkaline phosphatase (ALP) activity, bone-carboxyglutamic acid-containing protein (BGP) and calcium deposition were all thoroughly increased. These confirmed that the combination of PPy NWs and ES could accelerate MC3T3-E1 cells mature and osteogenesis. Hence, the PPy NWs coating was an electro bioactive coating and may have potential applications in the treatment of bone damage repairing and regeneration with ES.

One-step deposition of a melanin-like polymer on individual Escherichia coli cells exhibiting a special UV resistance effect

Melanin has an excellent ability to absorb UV radiation and to convert harmful radiant energy into heat or antioxidants. Therefore, melanin has a significant potential to endow fragile organisms such as recombinant or bioengineered microbes with a photoprotective ability. Inspired by mussel adhesive foot protein, a dopamine monomer (DA) was reported to self-polymerize into a melanin-like polymer, named polydopamine (PDA). Herein, combining the similarity to natural melanin and chemical adhesivity of the melanin-like PDA polymer, we prepared PDA encapsulated Escherichia coli cells (E. coli@PDA) with a simple method. The PDA encapsulation could retain E. coli cells viability and inhibited cell division. More importantly, the aromatic PDA shells could absorb the UV light and protect the cells against damage from UV radiation. After a prolonged exposure time to UV radiation, the protein stability, cellular metabolically active and cell viability of the E. coli cells were preserved. We believe that our work provides new insights for both fundamental research and applications of cell encapsulation for UV resistance.

Dopamine modified polyaniline with improved adhesion, dispersibility, and biocompatibility

Dopamine (DA), a biological neurotransmitter which has a similar structure to the essential adhesive component of mussel protein, was here used to modify polyaniline (PANI) via a one-step chemical oxidization method. The as-fabricated DA-PANI resulted from different DA to aniline (An) mole ratio showed different morphology. Compared to pure PANI, the modified PANI exhibited greatly enhanced adhesion force to the substrate. In addition, the biocompatibility and dispersibility of DA-modified PANI were also significantly improved compared with pure PANI. More importantly, the incorporation of poor conductive PDA did not enormously weaken the electrical conductivity of PANI, and it still showed good electrical conductivity as the DA/An mole ratio was not higher than 0.48.

Versatile method for the synthesis of porous nanostructured thin films of conducting polymers and their composites

A porous nanostructure of FeCl3 prepared by a simple evaporation process was used simultaneously as a template and oxidant to synthesize porous nanostructured thin films of almost all major classes of conducting polymers (CPs) and their composites.

Synthesis of Surface-Enhanced Raman Scattering-Active Gold Nanoflowers by 5-Hydroxytryptophan in Acidic Solution.

We demonstrated a one-step synthesis of gold nanoflowers by 5-hydroxytryptophan (5-HTP) in acidic solutions at room temperature. The synthesized nanoflowers are 400 nm in dimension consisting of a solid core and many small petal-like nanoparticles (30-50 nm) in various directions. The shape, size and surface morphology of the gold nanostructure could be tuned by controlling the molar ratio of 5-HTP to HAuCl4 and HCl concentration. Examination of the nanoparticles at different reaction stages with transmission electron microscopy (TEM) reveals the shape evolutionary process of the nanoflowers to get a better understanding on their possible formation mechanism. Additionally, these gold nanoflowers exhibit a high SERS performance because of textured surface which is expected to provide many active sites.

A RC model for facilitated transport in asymmetric membranes with fixed site carriers

A mathematical model for facilitated transport in asymmetric membranes with fixed site carriers was derived by assuming concentration fluctuation and an analogy between electron transport in resistor-capacitor circuit and mass transport in an asymmetric membrane of facilitated transport. In order to examine the validity of the model, bovine serum albumin fixed membranes were fabricated and experiment of facilitated transport of bilirubin was carried out in diffusion cell. The agreement between the theoretical and experimental results is exceptional.