Chung-Shu Wu

Real-Time and Label-Free Detection of the Prostate-Specific Antigen in Human Serum by a Polycrystalline Silicon Nanowire Field-Effect Transistor Biosensor

In this research, we used a polycrystalline silicon nanowire field-effect transistor (poly-Si NWFET) as a biosensor that employs the sidewall spacer technique instead of an expensive electron beam lithography method. When compared with commercial semiconductor processes, the sidewall spacer technique has the advantages of simplicity and low cost. In this study, we employed a novel poly-Si NWFET device for real-time, label-free, and ultrahigh-sensitivity detection of prostate-specific antigen (PSA) in human serum. Since serum proteome is very complex containing high levels of salts and other interfering compounds, we hereby developed a standard operating procedure for real-sample pretreatment to keep a proper pH value and ionic strength of the desalted serum and also utilized Tween 20 to serve as the passivation agent by surface modification on the NWFET to reduce nonspecific binding for medical diagnostic applications. We first modified 3-aminopropyltriethoxysilane on the surface of a poly-Si nanowire device followed by glutaraldehyde functionalization, and the PSA antibodies were immobilized on the aldehyde terminal. While PSA was prepared in the buffers to maintain an appropriate pH value and ionic strength, the results indicated that the sensor could detect trace PSA at less than 5 fg/mL in a microfluidic channel. The novel poly-Si NWFET is developed as a diagnostic platform for monitoring prostate cancer and predicting the risk of early biochemical relapse.

Size-modulated catalytic activity of enzyme–nanoparticle conjugates: a combined kinetic and theoretical study

A series of experiments were performed to systematically analyze the effect of nanoparticle (NP) size on the catalytic behavior of enzyme-NP conjugates, and a shielding model based on diffusion-collision theory was developed to explain the correlation between the size effects and the kinetic responses.

New Synthesis Route of Hydrogel through A Bioinspired Supramolecular Approach: Gelation, Binding Interaction, and in Vitro Dressing

Peptide-based supramolecular hydrogels have been comprehensively investigated in biomaterial applications because of their unique bioactivity, biofunctionality, and biocompatible features. However, the presence of organic building blocks in peptide-based hydrogels often results in low mechanical stability. To expand their practical use and range of applications, it is necessary to develop the tool kit available to prepare bioinspired, peptide-based supramolecular hydrogels with improved mechanical stability. In this paper, we present an innovative electrostatic and cross-linking approach in which naphthyl-Phe-Phe-Cys (NapFFC) oligopeptides are combined with gold nanoparticles (AuNPs) and calcium ions (Ca(2+)) to produce peptide-based supramolecular hydrogels. We further investigate the interactions among NapFFC, AuNPs and Ca(2+) by microscopy. The morphology of the nanofibrous network constructions and the binding forces exhibited from the hydrogel demonstrated that the combination of two mechanisms successfully enhanced the mechanical stability through the formation of a densely entangled fibrous network of peptide multimers that is attributed to the AuNP linkage and Ca(2+)-induced agglomeration. UV-vis spectrophotometry and fluorescence analysis were also used to demonstrate the enhanced stability of the hydrogel under various conditions such as thermal, solvent erosion, pH value and sonication. All results indicate that the presence of AuNPs and Ca(2+) can strengthen the prepared hydrogel by more than doubling the diameter of NapFFC nanofibers, enabling the formation of stronger frameworks and slowing the release of components. Further experiments confirmed that HeLa cells can grow on the bioinspired NapFFC-AuNP hydrogel and exhibit high cell viability and that these cells were killed on contact with a hydrogel containing a drug. Our peptide-based supramolecular hydrogels prepared from the observed electrostatic and cross-linking mechanisn exhibited a significantly improved mechanical stability, making them well suited to use as a drug carrier in hydrogel dressings and as extracellular materials (ECMs) for tissue engineering.

Novel Chemical Route to Prepare a New Polymer Blend Gate Dielectric for Flexible Low-Voltage Organic Thin-Film Transistor

An organic-organic blend thin film has been synthesized through the solution deposition of a triblock copolymer (Pluronic P123, EO20-PO70-EO20) and polystyrene (PS), which is called P123-PS for the blend film whose precursor solution was obtained with organic additives. In addition to having excellent insulating properties, these materials have satisfied other stringent requirements for an optimal flexible device: low-temperature fabrication, nontoxic, surface free of pinhole defect, compatibility with organic semiconductors, and mechanical flexibility. Atomic force microscope measurements revealed that the optimized P123-PS blend film was uniform, crack-free, and highly resistant to moisture absorption on polyimide (PI) substrate. The film was well-adhered to the flexible Au/Cr/PI substrate for device application as a stable insulator, which was likely due to the strong molecular assembly that includes both hydrophilic and hydrophobic effects from the high molecular weights. The contact angle measurements for the P123-PS surface indicated that the system had a good hydrophobic surface with a total surface free energy of approximately 19.6 mJ m(-2). The dielectric properties of P123-PS were characterized in a cross-linked metal-insulator-metal structured device on the PI substrate by leakage current, capacitance, and dielectric constant measurements. The P123-PS film showed an average low leakage current density value of approximately 10(-10) A cm(-2) at 5-10 MV cm(-1) and large capacitance of 88.2 nF cm(-2) at 1 MHz, and the calculated dielectric constant was 2.7. In addition, we demonstrated an organic thin-film transistor (OTFT) device on a flexible PI substrate using the P123-PS as the gate dielectric layer and pentacene as the channel layer. The OTFT showed good saturation mobility (0.16 cm(2) V(-1) s(-1)) and an on-to-off current ratio of 5 × 10(5). The OTFT should operate under bending conditions; therefore flexibility tests for two types of bending modes (tensile and compressive) were also performed successfully.

Thin‐Film Composite Materials as a Dielectric Layer for Flexible Metal–Insulator–Metal Capacitors

A new organic-organic nanoscale composite thin-film (NCTF) dielectric has been synthesized by solution deposition of 1-bromoadamantane and triblock copolymer (Pluronic P123, BASF, EO20-PO70-EO20), in which the precursor solution has been achieved with organic additives. We have used a sol-gel process to make a metal-insulator-metal capacitor (MIM) comprising a nanoscale (10 nm-thick) thin-film on a flexible polyimide (PI) substrate at room temperature. Scanning electron microscope and atomic force microscope revealed that the deposited NCTFs were crack-free, uniform, highly resistant to moisture absorption, and well adhered on the Au-Cr/PI. The electrical properties of 1-bromoadamantane-P123 NCTF were characterized by dielectric constant, capacitance, and leakage current measurements. The 1-bromoadamantane-P123 NCTF on the PI substrate showed a low leakage current density of 5.5 x 10(-11) A cm(-2) and good capacitance of 2.4 fF at 1 MHz. In addition, the calculated dielectric constant of 1-bromoadamantane-P123 NCTF was 1.9, making them suitable candidates for use in future flexible electronic devices as a stable intermetal dielectric. The electrical insulating properties of 1-bromoadamantane-P123 NCTF have been improved due to the optimized dipole moments of the van der Waals interactions.

Polystyrene-block-poly(methylmethacrylate) composite material film as a gate dielectric for plastic thin-film transistor applications

We report a simple approach to fabricate an organic–inorganic hybrid gate insulator based n-type thin-film transistor (TFT) on a plastic polyimide (PI) sheet at room temperature using an appropriate composition of commercially available polymers and block copolymer surfactant. The composite material film namely; polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) is readily deposited as a gate dielectric with zinc oxide (ZnO) as a semiconductor layer. This new dielectric material film exhibits high surface energy, high air stability, very low leakage current density and better dielectric constant as compared to the conventional polymer dielectrics. This plastic ZnO–TFT combines the advantages of a high-mobility transparent inorganic semiconductor with an ultrathin high-capacitance and low-leakage PS-b-PMMA composite gate dielectric. Fourier transform infrared (FT-IR) spectrum analysis is used for the PS-b-PMMA film to confirm the presence of functional components in this composite material film. The contact angle measurements for three test liquids (e.g., distilled water, ethylene glycol and diiodomethane) reveal that the composite dielectric materials film is nearly hydrophobic and the calculated surface energy is 35.05 mJ m−2. The resulting TFT exhibits excellent operating characteristics at VDS = 10 V with a drain–source current on/off modulation ratio (Ion/Ioff) of 3.12 × 106 and a carrier mobility of 2.48 cm2 V−1 s−1. Moreover in the bending mode and in a normal environment, the device remained undistorted and shows better reliability and performance, while the thickness of PS-b-PMMA is about 28 nm. The results have suggested a new and easy approach for achieving transparent and functionally bendable optoelectronics devices.

Facile synthesis of a biocompatible silver nanoparticle derived tripeptide supramolecular hydrogel for antibacterial wound dressings

Realizing the widespread demand for biocompatible supramolecular hydrogel based wound dressings, we have developed an N-terminally 2(naphthalen-6-yl)acetic acid (Nap) protected Phe–Phe–Cys peptide (Nap-FFC) using a liquid phase method. This Nap-FFC peptide was used to design a supramolecular hydrogel via a self-assembling process. The Nap-FFC short peptides produced stable and transparent silver nanoparticle-based hydrogels (AgNPs@Nap-FFC) wherein the self-assembled Nap-FFC nanofibers acted as scaffolds for the mineralization of silver nanoparticles (AgNPs) and stabilizers of the synthesized AgNPs. The resultant AgNPs@Nap-FFC nanocomposites were characterized using ultraviolet-visible spectrophotometry (UV-vis spectroscopy), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX) studies. The AgNPs@Nap-FFC nanocomposites showed excellent monodispersity, long term stability, and functional flexibility in comparison to other AgNP based nanocomposites. Furthermore, AgNPs@Nap-FFC exhibited strong inhibition against both Gram-positive (methicillin-resistant Staphylococcus aureus) and Gram-negative (Acinetobacter baumannii) bacteria and, most importantly, they showed favorable biocompatibility towards human cervical carcinoma cells (HeLa cells). Hence, this study implies that AgNPs@Nap-FFC nanocomposites can easily be prepared in a cost-effective manner and can be used effectively for future antibacterial wound dressings.

Control of active semiconducting layer packing in organic thin film transistors through synthetic tailoring of dielectric materials

Apart from the development of new dielectric and semiconductor materials, the semiconductor–dielectric interface study is also very important for the optimum performance of organic thin film transistors (OTFTs). Herein, we have reported the detailed synthesis of a whole new family of dielectric materials which are 1,3,5,7-tetrabromoadamantane; 1,3,5,7-tetrachloroadamanatane; 1,3,5,7-tetraiodoadamantane and 1,3,5,7-tetrauraciladamantane (AdUr4). The unique ability of these molecules to undergo supramolecular thin film formation at low temperature, was analysed for their potential use as an insulator in organic electronic devices. Owing to the good leakage current density property shown by AdUr4 dielectric material it was further employed as a gate dielectric in regioregular poly(3-hexylthiophene), (P3HT) based OTFT. This OTFT device which was fabricated on a flexible PI plastic substrate has shown a good on/off current ratio (e.g., 2.18 × 104) and high mobility (e.g., 0.15 cm2 V−1 s−1). The semiconductor–dielectric interface study, has revealed that the AdUr4 gate dielectric layer has guided the P3HT molecular chain domains to undergo edge-on orientation, which is the charge transport direction in OTFTs. In this process, the grazing incidence X-ray diffraction (GI-XRD) analysis and AFM study was also employed.

Prostate Cancer Marker Sensing Under Nanostructural Biochip Technique

A silicon nanobelt field effect transistor (SiNBFET) device was proposed as an alternating platform of ultrasensitive biosensor, and apply to the label-free detection and early diagnosis of the prostate specific antigen (PSA). The designed SiNB-FET molecule sensor demonstrated real-time, label-free, and high-selective properties in detecting biomolecules. The novel back-gate SiNB-FET was fabricated by using the state-of-the-art complementary metal oxide semiconductor (CMOS) manufacturing technology. The shrank nanobelt structure with high surface-to-volume ratio and individual back-gate controlling was achieved by the local-oxidation of silicon (LOCOS) process. The probe molecule was sequentially immobilized onto the device surface for the purpose of target molecule sensing. Those molecules bearing with charge characteristics significantly influenced the charge carrier in the device channel. Hence, the target PSA can be easily detected from the shift of device’s electrical property. In this research, the operating condition of device’s gate controlling voltage was carefully studied. In addition, the molecular amplification method was developed to enhance the method’s sensitivity. Finally, real samples from the hospital site were evaluated to characterize the concentration. We have demonstrated the detection capability of PSA by the SiNB-FET, and results show that the nanobelt biochip will be applied to the clinical diagnosis, and verify its feasibility on the ultrasensitive diagnosis of prostate cancer in the future.

Catalytic behaviors in modulating enzymatic activity through different-sized gold nanoparticles

We have demonstrated that gold nanoparticles (AuNPs) can effectively associate with enzyme through spontaneous adsorption to afford supramolecular complexes, resulting in a significant increase of its enzymatic activity. In this work, we embarked on a study of the interactions between the different-sized AuNPs and the substrate through quantifying the kinetic parameters (Kcat and KM). The diversity of size allows us to probe the role of catalytic behaviors in modulating enzymatic activity.