Ching-Jung Chen

The surface modification of silver nanoparticles by phosphoryl disulfides for improved biocompatibility and intracellular uptake

In order to enhance the biocompatibility and cell affinity of metal nanoparticles for biosensing and drug delivering applications, we prepared the phospholipid derivatives containing disulfide groups to modify silver nanoparticle surfaces. By adding sodium borohydride to reduce both disulfide bonds of the derivatives and silver ions simultaneously, the generated thiol groups can be reacted with newborn silver atoms immediately to generate nanoclusters. The assemblies consisted of either phosphorylcholine (PC) or phosphorylethanolamine (PE) head groups, which made the silver clusters biocompatibile. Transmission electron microscope (TEM) and optical absorption spectra assisted in modulating reaction conditions, demonstrating that a surfactant/Ag ratio of 0.4 led to the formation of uniform, well-dispersed spherical particles about 3.8 nm in diameter. X-ray photoelectron spectra and infrared spectra also illustrated the elemental and molecular structures of nanoparticles. The insertion of rhodamine dye into the surfactant layer enabled the nanoparticles to be used as a fluorescent probe. In cell culture tests, the nanoparticles were internalized into platelet or fibroblast cells in a short period of incubation without harming the cells.

Surface plasmon resonance biosensor with high anti-fouling ability for the detection of cardiac marker troponin T

Designing a surface recognition layer with high anti-fouling ability, high affinity, and high specificity is an important issue to produce high sensitivity biosensing transducers. In this study, a self-assembled monolayer (SAM) consisting of a homogeneous mixture of oligo(ethylene glycol) (OEG)-terminated alkanethiolate and mercaptohexadecanoic acid (MHDA) on Au was employed for immobilizing troponin T antibody and applied in detecting cardiac troponin T by using surface plasmon resonance (SPR). The mixed SAM showed no phase segregation and exhibited human serum albumin resistance, particularly with an antibody-immobilized surface. X-ray photoemission spectra revealed that the chemical composition ratio of OEG to the mixed SAM was 69% and the OEG packing density was 82%. The specific binding of troponin T on the designed surface indicated a good linear correlation (R=0.991, P<0.0009) at concentrations lower than 50 μgmL(-1) with the limit of detection of 100 ngmL(-1) using a SPR measuring instrument. It is concluded that the mixed SAM functions as designed since it has high detection capability, high accuracy and reproducibility, as well as shows strong potential to be applied in rapid clinical diagnosis for label-free detection within 2 min.

Impedimetric method for measuring ultra-low E. coli concentrations in human urine.

In this study, we developed an interdigitated gold microelectrode-based impedance sensor to detect Escherichia coli (E. coli) in human urine samples for urinary tract infection (UTI) diagnosis. E. coli growth in human urine samples was successfully monitored during a 12-h culture, and the results showed that the maximum relative changes could be measured at 10Hz. An equivalent electrical circuit model was used for evaluating the variations in impedance characteristics of bacterial growth. The equivalent circuit analysis indicated that the change in impedance values at low frequencies was caused by double layer capacitance due to bacterial attachment and formation of biofilm on electrode surface in urine. A linear relationship between the impedance change and initial E. coli concentration was obtained with the coefficient of determination R(2)>0.90 at various growth times of 1, 3, 5, 7, 9 and 12h in urine. Thus our sensor is capable of detecting a wide range of E. coli concentration, 7×10(0) to 7×10(8) cells/ml, in urine samples with high sensitivity.

Screen-printed carbon electrode-based electrochemical immunosensor for rapid detection of microalbuminuria.

A urinary microalbumin test is used to detect early signs of kidney damage in people who have a risk of chronic kidney disease, such as those with diabetes or hypertension. In this study, we developed a screen-printed carbon electrode-based immunosensor for the detection of microalbumin in urine. Anti-human albumin antibodies were immobilized on the screen-printed sensor surface by the covalent immobilization method. Cyclic voltammetry (CV) and scanning electron microscopy with an energy dispersive spectroscopical (SEM-EDS) analysis demonstrated that the modification process was well performed. Chronoamperometric (CA) electrochemical measurement technique was employed for the quantitative detection of albumin. The electrochemical measurements performed with some possible interfering compounds normally present in urine (ascorbic acid, uric acid, glucose and creatinine samples) demonstrated a high specificity and selectivity of this immunosensor in albumin detection. Under optimum conditions, the immunosensor can detect urinary albumin in a wide linear range from 10 µg/ml to 300 µg/ml with a detection limit of 9.7 µg/ml. The excellent performance of this immunosensor was confirmed by analyzing microalbumin in urine samples; the results were in good agreement with those obtained by the standard immunoturbidimetric method. The biosensor proposed herein is easy to prepare and can be used for low-cost, rapid, and sensitive screening of microalbuminuria. This approach provides a promising platform for developing clinical point-of-care diagnostic applications.

Resonant efficiency improvement design of piezoelectric biosensor for bacteria gravimetric sensing

The piezoelectric biosensor have been widely used in ultra-small mass detection of biomolecular, based on PZT piezoelectric material can create a variety of compositions geometrically; it could widely develop a high-frequency resonator and measure the change of the slightest mass while improve the limited detection simultaneously. Therefore, the piezoelectric biosensor of this study was fabricated by a spin-coating method and backside etching process for improving the characteristic of piezoelectric biosensor. The result exhibited that the 250 μm × 250 μm working size has the most favorable piezoelectric characteristic. The tunability was approximately 38.56 % and it showed that reducing the substrate thickness could obtain a clear resonance signal in a range of 60 to 380 MHz. In theory calculated for gravimetric sensing, it could achieve 0.1 ng sensing sensitivity. In gravimetric sensing, the sensing range was between 50,000~100,000 CFU/ml. Sensing range was lower in clinical urinary tract infection (100,000 CFU/ml), thus demonstrating its usefulness for preventive medicine. It can understand the piezoelectric sensor of this study has potential application in the future for biomedical gravimetric sensing.

Concept for E.coli detection using interdigitated microelectrode impedance sensor

This paper presents the concept to detect Escherichia coli O157:H7 based on electrochemical impedance spectroscopy at interdigitated microelectrode. Interdigitated microelectrode structures was designed and fabricated, with glass as substrate material and gold electrodes. The performance of the sensors was studied by measuring the capacitance in air and impedance spectra in DI water. The feasibility of the fabricated sensor for detecting different concentrations of Escherichia coli in water was demonstrated. Electrochemical impedance spectroscopy (EIS) was employed as the detection technique. The impedance based response significant change for different E.coli concentrations in the frequency range between 1 kHz to 100 kHz.

A Flexible Interdigital Electrode Used in Skin Penetration Promotion and Evaluation with Electroporation and Reverse Iontophoresis Synergistically

Skin penetration is related to efficiencies of drug delivery or ISF extraction. Normally, the macro-electrode is employed in skin permeability promotion and evaluation, which has the disadvantages of easily causing skin damage when using electroporation or reverse iontophoresis by alone; furthermore, it has large measurement error, low sensitivity, and difficulty in integration. To resolve these issues, this paper presents a flexible interdigital microelectrode for evaluating skin penetration by sensing impedance and a method of synergistical combination of electroporation and reverse iontophoresis to promote skin penetration. First, a flexible interdigital microelectrode was designed with a minimal configuration circuit of electroporation and reverse iontophoresis for future wearable application. Due to the variation of the skin impedance correlated with many factors, relative changes of it were recorded at the end of supply, different voltage, or constant current, times, and duration. It is found that the better results can be obtained by using electroporation for 5 min then reverse iontophoresis for 12 min. By synergistically using electroporation and reverse iontophoresis, the penetration of skin is promoted. The results tested in vivo suggest that the developed microelectrode can be applied to evaluate and promote the skin penetration and the designed method promises to leave the skin without damage. The electrode and the method may be beneficial for designing noninvasive glucose sensors.

Preparation and evaluation of chitosan biocompatible electronic skin

Abstract Polydimethylsiloxane (PDMS) is often used in flexible electronic skin, due to their non toxic and tough. However, the lack of degradation and cell biocompatibility of PDMS would limit the potential use in the biological field. To overcome the limitation, PDMS was modified by surface treatment for enhancing cell adhesion and proliferation. This research is focused on preparation and evaluation of novel chitosan biocompatible electronic skin. Chitosan electronic skin was prepared by a thermal induced phase separation method, following treatment with NaOH gelating agent, followed by analyzing the surface morphology, swelling behavior, mechanical strength, degradation rate. The electrode was produced by screen printing technique, followed by analyzing the adhesion between the ink and cell biocompatibility. From scanning electron microscope (SEM) observations, NaOH gelated chitosan skin had the smooth surface morphology. The swelling ratio of all chitosan skin gelated by NaOH were less than 5%. The chitosan skin, prepared by 300k kDa chitosan gelated by NaOH for 3hr, had the smallest swelling ratio. Furthermore, its mechanical strength showed the highest value of Young’s modulus (∼151 kPa). It indicated that 300 kD chitosan skin gelated by NaOH for 3hr had better size stability. All chitosan skins degraded about 20% of initial weight after 40 days in vitro shaking test. The adhesion strength of the silver inks on the surface of chitosan was better than carbon ink, and the electrical characteristic is almost the same with commercial polycarbonate (PC) substrate. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay and SEM observation indicated that chitosan skin with silver electrode showed the cell biocompatibility. By further increasing the application of both screen imprinting technique and biopolymer, the idea of interdisciplinary can be achieved and it would be a creative revolution to the field of wearable device into tissue engineering.

Angle-Scanning Surface Plasmon Resonance System with 3D Printed Components for Biorecognition Investigation

Surface plasmon resonance (SPR) is a real-time, label-free, and high-sensitive detection technology. SPR has been widely used in many applications such as biomolecular interaction analysis, environmental monitoring, and medical diagnostics. However, conventional SPR sensor systems usually require expensive equipment and complicated optics. In this paper, we have demonstrated a rapid prototyping of angle-scanning SPR for bioanalytical investigation. Rapid prototyping was attained by utilizing the FDM (fused deposition modeling) based 3D (three-dimensional) printing technology. Two rotating platforms were employed to drive the laser source and photodiode, respectively. A temperature regulation unit was incorporated to maintain the system temperature in order to reduce the temperature effect. The proposed SPR rapid prototyping yielded a refractive index resolution of 6.4×10−6 RIU (refractive index unit), and the biotin-avidin system validated the kinetics parameters measurement capability. The obtained results indicated that the FDM 3D printing has great potential for developing rapid-prototyping SPR system.

Ultra-low charge transfer resistance carbons by one-pot hydrothermal method for glucose sensing

Hydrothermal carbon (HTC) is typically well-dispersed, but it remains a great challenge for HTC to become conductive. Co-doping with heteroatoms has been confirmed to be an effective strategy to significantly promote the electrical conductivity of carbon. Moreover, there is no simple and green method to construct sensitive HTC based electrochemical biosensors until now. In this paper, N and S dual-doped carbon (NS-C) with ultra-low charge transfer resistance is easily synthesized from L-cysteine and glucose in a hydrothermal reaction system. The morphology, structural properties and electrochemical properties of the as-prepared NS-C are analyzed. In comparison with the undoped hydrothermal (UC) modified glassy carbon electrode (GCE), the charge transfer resistance of UC (476 Ω) is ten times the value of NS-C (46 Ω. The developed biosensor shows a better performance to detect glucose in a wide concentration range (50-2500 μmol L-1) with the detection limit of 1.77 ^mol L-1 (S/N=3) and a high sensitivity (0.0554 μA cm-2 μmol-1 L). The apparent Michaelis-Menten constant value of GCE/NS-C/GOx/nafion modified electrode is 0.769 mmol L-1, indicating a high affinity of glucose oxidase to glucose. These results demonstrate that the hydrothermal method is an effective way for preparing high electrical conductivity carbon with excellent performances in biosensor application.摘要热碳材料具有较好的水溶性, 但是通常表现为绝缘性, 因此提高水热碳材料的导电性仍然是一个重大挑战. 化学掺杂已经被证实 能够显著提高碳材料的导电性, 但目前尚没有一种简单且绿色的方法制备高灵敏度水热碳基的电化学传感器. 本文在水热反应体系中用 L-半胱氨酸和葡萄糖合成了超低电子转移阻抗的氮硫掺杂碳材料, 随后分析了材料的形貌、结构和电化学性质. 氮硫掺杂碳修饰电极电 子转移阻抗(46 Ω)大约是非掺杂碳修饰电极(476 Ω)的1/10. 氮硫掺杂碳材料制备的葡萄糖传感器具有较宽线性范围(50–2500 μmol L−1), 低的检测限(1.77 μ mol L−1, S/N=3)和高的灵敏度(0.0554 μ A cm−2 μmol −1 L). GCE/NS-C/GOx/nafion电极的米氏常数为0.769 mmol L−1, 表 明N S-C 负载的葡萄糖氧化酶(GOx)对葡萄糖具有较高亲和力. 本研究提出以水热法合成具有高电导性的碳材料, 并应用于高性能的葡萄糖传感器.