In previous work a short chain SAM, 4,4-Dithiodibutyric Acid (DTBA) was found to be a thin monolayer in protein chips. However, obtaining uniform fluorescent intensity remains difficult because water-soluble carbodiimides (EDC) in an aqueous system cause the hydrolysis of N-hydroxysuccinimide ester (NHS esters). The hydrolysis of NHS esters reduces coupling yields and therefore reduces the fluorescent intensity of protein chips. The NHS can increase the stability of active intermediate resulting from the reaction of EDC and NHS, but the ratio of the concentration of EDC to that of NHS strongly affects this stability. The effects of the solvents used in the washing step are studied to solve this problem. The results reveal that PBST (PBS + 5% Tween20) is more effective in reducing the hydrolysis of NHS esters than deionized water. Additionally, the effects of 3:1 and 5:2 EDC/NHS ratios on the chips are examined. The 3:1 EDC/NHS ratio yields a higher fluorescent intensity than the 5:2 ratio. The effects on the chips of dissolving EDC in DI water, DI water + 0.1 M MES and alcohol are also investigated. The results show that alcohol provides higher fluorescent intensity than other solvents and the reaction time of 4 h yields a high fluorescent intensity with 3:1 EDC/NHS ratio. A modified fabrication process of protein chips using 4,4-DTBA is developed. In this work, 160 mM 4,4-DTBA is used as a self-assembled monolayer in the fabrication of protein chips. Experiments to characterize 4,4-DTBA are performed by contact angle goniometry and Fourier transform infrared spectroscopy (FTIR). Furthermore, the immobilized protein A-FITC (fluorescein isothiocyanate) is adopted in fluorescent assays.
Although 3-aminopropyltriethoxysilane (APTES) is widely adopted as a monolayer in biosensors, experimental silanization takes at least 1 h at high temperature. Therefore, the feasibility of the silanization with APTES in a short reaction time and at room temperature was investigated. The surface modification of glass slides using a self-assembled monolayer of APTES with a concentration of 10% was studied by immobilizing FITC. APTES was successfully immobilized on the glass slide. The effect of reaction temperature and time of silanization were investigated. Various silanization conditions of APTES were examined by contact angle measurement and fluorescence microscopy. The surface of glass patterns with a gold thin film as background was characterized by determining the fluorescent intensities following the immobilization of fluorescein isothiocyanate (FITC), protein A-FITC, antimouse IgG-FITC and sheep anti-bovine albumin-FITC. The normalized fluorescent intensity indicated that a short period (4 min) of silanization at 25 degrees C suffices to form an APTES thin film by the immobilization of protein A on a glass surface. Such a condition does not require microheaters and temperature sensors in a microfluidic system, which will significantly reduce the manufacturing process, cost, and reaction time in the future.
This work presents a driving system for a peristaltic micropump that is based on piezoelectric actuation. The effects of the actuation sequence on pump performance are also considered. A valveless peristaltic micropump based on piezoelectric actuation is designed and fabricated using microelectromechanical system technology. The pump has three parts--silicon, Pyrex glass and commercially available bulk PZT (lead zirconate titanate) chips. The peristaltic micropump actuated by PZT chips comprises three chambers that are in series. The driving system consists of an ATmega 8535 microprocessor, a high voltage power supply, three differential amplifiers, a phase controller, an A/D converter, a 555 oscillator and an LCD module. It is supplied via a 110 Vrms 60-Hz AC line and is programmable. The system can produce step-function signals with voltages of up to 100 V pp and frequencies ranging from 10 Hz to 1 kHz, as the inputs for the pump. Fluid pumping with air is successfully demonstrated. Additionally, 3-, 4-and 6-phase actuation sequences for the pump are designed and used to study the effects on pump performance, as revealed by the flow rate and the displacement of a pump diaphragm. The experimental results show that the flow rate and the displacement of the diaphragm actuated by the 4-phase sequence exceed those actuated by the 3-and 6-phase sequences. A flow rate of 17.6 ll min À1 and a displacement of 2.91 lm (peak-to-peak) in 4-phase peristaltic motion are achieved at 100 Hz and 100 V pp . The results demonstrate that the pump actuated in the 4-phase sequence is the most efficient. Consequently, the actuation sequences can affect the pump performance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.