Papers by saowapak teerasong
CURRENT APPLIED SCIENCE AND TECHNOLOGY
Controlling drug release using a nanocomposite method is crucial; however, burst release must be ... more Controlling drug release using a nanocomposite method is crucial; however, burst release must be avoided in order to obtain effective controllable drug release. In this study, poly(vinyl) alcohol/polyoxalate/Span-80 (PVA/ POX/ Span-80) composite nanofibers loaded with Rhodamine B were produced using emulsion electrospinning. The objective of this work was to evaluate the cooperative roles of POX and Span-80 on nanofibrous scaffold stability and drug release regulation by monitoring Rhodamine B release performance from electrospun composite nanofibers. The microstructure and hydrophilic properties of the emulsion electrospun nanofibers were studied using scanning electron microscopy (SEM), water contact angle, and swelling tests. According to the results, increasing the POX content had a significant effect on the size of nanofibers. The water contact angles increased as the POX content increased. The release of Rhodamine B was governed by a two-stage diffusion mechanism that was grea...
Insight into the Covalently Oriented Immobilization of Antibodies on Gold Nanoparticle Probes to Improve Sensitivity in the Colorimetric Detection of Listeria monocytogenes
Bioconjugate Chemistry
International Journal of Electrochemical Science, 2019
A graphene modified carbon paste sensor (or so-called graphene based sensor) was developed for el... more A graphene modified carbon paste sensor (or so-called graphene based sensor) was developed for electrochemical detection of hydroquinone. The sensor was fast fabricated using screen-printing technique. By integrating three fundamental electrodes on a single device, the sensor is small and portable. A determination is based on a one drop analysis. A 60 L-drop of sample was placed onto the sensor prior to cyclic voltammetric measurement. The method relies on green analysis since it lowers the consumption of sample and waste generation. Under the optimal conditions, a linear calibration was achieved in range of 1.0 10-4 to 5.0 10-3 M hydroquinone. The detection limit was 7 10-5 M, a sensitive adequate for measuring hydroquinone in cosmetic products. The sensor provided good precision (%RSD = 2.78) and accuracy (recoveries = 87-114%), with analysis times of less than a minute. The sensor was applied to determine the presence of hydroquinone in whitening creams. The results obtained from the developed sensor satisfactorily agreed with the HPLC method, indicating the reliability of the method. Due to its advantages in terms of rapidity, low-cost and portability, the device is a viable choice for on-site screening for hydroquinone contamination in whitening products.
A rapid cotton swab for on-site screening of coloring curcumin on durian skin: food safety aspects
Analytical Sciences
Direct determination of ethanol in alcoholic beverages based on its anti-aggregation of melamine-silver nanoparticle assembly
Talanta
A new mechanism for resonance Rayleigh scattering detection of minoxidil based on catalytic oxidation of silver nanoparticles
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2022
Use of the predict-observe-explain teaching sequence for flow-based technique and new development of two flow
The octanol-water partition coefficient (Pow) is widely used to assessment of lipophilicity of dr... more The octanol-water partition coefficient (Pow) is widely used to assessment of lipophilicity of drug. The Pow can be measured by determining the ratio of the concentration of the drug in octanol to its concentration in water at equilibrium. In the standard method, two calibration curves are required in order to obtain the concentration of drug in the two phases. The procedure is thus tedious and time consuming. In this work, a simple approach for determining the Pow of drug is described. Only the absorbance of one phase and volumes of octanol and water are used in the calculation; calibration curves are no longer required, making the procedure much more convenient. The method was applied to examples of hydrophobic and hydrophilic drugs. The Pow values obtained by our method agreed well with literature values (R2 = 0.998). This method is simple and capable for screening new drugs in a stage of drug discovery.
Development of a Predict-observe-explain Strategy for Teaching Flow Injection at Undergraduate Chemistry
The International Journal of Learning: Annual Review, 2010
Journal of Nanomaterials, 2017
The results of releasing a drug in a burst are unpredictable and one of the inherent drawbacks of... more The results of releasing a drug in a burst are unpredictable and one of the inherent drawbacks of using nanocarriers. Here, photoresponsive cationic gold nanoparticles to stabilize diacetylenic nanocapsules enabling photoregulated release of payloads are reported. The fabrication of these nanocapsules relied on an electrostatic interaction of a negatively charged diacetylenic core and a positively charged gold nanoparticle shell. Gold nanoparticles with photoresponsive ligands on their surfaces act as both hydrophobic core stabilizers and gatekeepers of the nanocapsules, while their polydiacetylene cores serve as hydrophobic drug carriers that can be tuned using UV irradiation. The morphology of nanocapsules was analyzed using TEM and dynamic light scattering. The resultant nanocapsules had a spherical shape with an average diameter of 152.9 ± 6.7 nm. Upon UV irradiation, the nanocapsules lost their integrity and an encapsulated model compound was released through diffusion. The rel...
Sensors and Actuators B: Chemical, 2017
Research highlights A sensitive resonance Rayleigh scattering method for determination of Hg 2+... more Research highlights A sensitive resonance Rayleigh scattering method for determination of Hg 2+ was developed. The reaction was simply performed by in-situ mixing of gold nanorods, ssDNA and Hg 2+ in one pot. The reaction took place rapidly and the analysis could be completed within 5 min. The method offers a low detection limit of 0.23 nM.
Analytical Sciences, 2016
A simple and rapid method was developed for the detection of poly(diallyldimethylammonium chlorid... more A simple and rapid method was developed for the detection of poly(diallyldimethylammonium chloride) (PDADMAC) using citrate-capped silver nanoparticles (AgNPs). Detection was based on anti-aggregation of AgNPs in phosphate buffer caused by PDADMAC. Due to its positive charges, PDADMAC was adsorbed onto AgNPs via electrostatic interaction with citrate, which resulted in the charges at the particle surfaces to become positive and caused repulsion among particles. Furthermore, long-chain PDADMAC provided steric hindrance. These two effects promoted the dispersion of AgNPs in the phosphate buffer. A change in the state of dispersion influenced the surface plasmon resonance (SPR) of AgNPs. Therefore, in this work, the concentration of PDADMAC was determined by monitoring changes in absorbance (at 396 nm) caused by SPR of AgNPs. Under optimal conditions, the calibration was linear over the range of 1 to 100 mg L-1 with a detection limit of 0.7 mg L-1. Satisfactory precision was obtained (RSD = 2.8%). This method was successfully applied to the determination of PDADMAC in tap water samples. The recoveries ranged from 86.0-107.5%.
Sensors and Actuators B: Chemical, 2016
A novel, simple and rapid colorimetric method for determination of gamma-aminobutyric acid (GABA)... more A novel, simple and rapid colorimetric method for determination of gamma-aminobutyric acid (GABA) was developed using a negatively charged citrate-capped silver nanoparticle (AgNP) probe. At an acidic pH of 3.8, GABA had a positive charge due to a protonation of amine groups. Therefore GABA could induce an aggregation of AgNPs due to electrostatic interaction. This caused a decrease in the surface plasmon resonance spectra of the colloidal solution at wavelength of 390 nm with a slight red shift. At the same time, the color of the suspension turned from yellow to green upon aggregation. Quantification of GABA was done spectrophotometrically. Under optimum conditions, the method showed a linear calibration in range of 100-500 mgL-1 GABA, with a detection limit of 57.7 mgL-1. The method was successfully applied to measure GABA quantities in dietary supplements.
Sequential injection for determination of gamma-aminobutyric acid based on its effect on second order light scattering of silver nanoparticles
Journal of Food Composition and Analysis, 2016
Abstract An automated sequential injection (SI) with second order light scattering (SOS) detectio... more Abstract An automated sequential injection (SI) with second order light scattering (SOS) detection for determination of gamma-aminobutyric acid (GABA) was developed. Quantitation is based on electrostatic interaction between GABA and citrate-capped silver nanoparticles (AgNPs). In acetate buffer at pH 3.8, the positively charged GABA induces the nanoparticles to aggregate. This results in a change of light scattering monitored using a spectrofluorometer. In this work, working standard solutions of GABA were prepared in-line by the SI system pumping appropriate volumes of a stock solution of GABA and acetate buffer into a holding coil. Solution of AgNPs was subsequently drawn into the coil. The reaction zone was then transferred to the spectrofluorometer, set with excitation and detection wavelengths at 300 and 600 nm, respectively. Under optimised condition, the SOS intensity was proportional to the concentration of GABA. As a result, a linear curve was obtained in the range of 100–400 mg L −1 GABA, with a lower limit of detection of 39.6 mg L ‐1 . Good precision of analysis was achieved, with 0.6 and 3.3% relative standard deviation (RSD) for external calibration ( n = 5) and standard addition ( n = 3), respectively. The developed method was successfully applied for quantification of GABA in dietary supplements (2 samples) and samples of instant green tea (2 samples).
Journal of Experimental Nanoscience, 2015
In this work, a silver nanoparticle (AgNP) coated glass slide was developed as a device for sensi... more In this work, a silver nanoparticle (AgNP) coated glass slide was developed as a device for sensing hydrogen peroxide. AgNPs were synthesised using borohydride reduction with a citrate stabiliser, resulting in a negatively charged stabilised particle surface. The particles were attached to the glass surface using the layerby-layer (LbL) technique. Poly (diallyldimethylammonium chloride) and poly (styrene sulphonate) were used as cationic and anionic polyelectrolyte layers, respectively. The glass slide was modified with polyelectrolytes leaving a cationic layer on the top surface. The AgNPs were subsequently deposited on the slide via electrostatic interaction. As a result, a dark yellow film of AgNPs was obtained with maximum absorption at 410 nm. Film fabrication based on LbL assembly provided acceptable reproducibility (relative standard deviation D 6.5%). The fabricated film had long-term stability (>6 weeks). A very small quantity of AgNPs was used in this method. Fabrication was performed under ambient conditions. Therefore this fabrication was considered as a green method. The AgNP modified slide was developed to sense hydrogen peroxide. Detection is based upon oxidation of AgNPs by hydrogen peroxide. This results in a change in colour of the film from dark yellow to colourless. Linear calibration was obtained over the range of 1.0-100.0 mM of hydrogen peroxide. The device was successfully used for measuring hydrogen peroxide in urine.
Analytica Chimica Acta, 2015
An automatedzone-microfluidic system is presented for screening of octanol-water partition coeffi... more An automatedzone-microfluidic system is presented for screening of octanol-water partition coefficient (P ow). Requires onlyone-phase measurement. Vertically aligned holding column improves eliminates zone breakage.
Talanta, 2010
This work presents a flow analysis method for direct quantitation of calcium carbonate in cement ... more This work presents a flow analysis method for direct quantitation of calcium carbonate in cement without pretreatment of the sample. The method is based on online vaporization of CO 2 gas following acidification of the sample inside a small chamber that has a flow of acceptor solution passing around it. Solubilization of the CO 2 gas into the acceptor stream changes the conductivity of the acceptor solution causing an increase of signal at the capacitively coupled contactless conductivity detection (C 4 D) placed at the outlet of the vaporization chamber. This chamber is an adaption from previous work reported on 'membraneless vaporization' (MBL-VP). The method can be used in the quality control of production of mixed cement. These cement materials usually have calcium carbonate contents at high concentration range (e.g., 33-99% (w/w) CaCO 3). Analysis of samples by this method is direct and convenient as it requires no sample pretreatment. The method is low-cost with satisfactory accuracy and acceptable precision.
Talanta, 2011
This work presents a new flow-based coupled electrochemical technique for evaluation of "total an... more This work presents a new flow-based coupled electrochemical technique for evaluation of "total antioxidant capacity (TAC)". A sequential injection (SI) with amperometric detection was applied to the TAC analysis of commercial instant ginger infusion beverages using 2,2-azino-bis(3-ethylbenzothiazoline-6sulfonic acid) (ABTS) assay. Besides having chromogenic properties, the ABTS reagent behaves as an electroactive species at the glassy carbon electrode in phosphate buffer pH 7.0, the decrease of the cathodic current signal of the ABTS • + radical after reaction with antioxidants can be monitored. The SI system, furnished with an in-house electrochemical detection cell (ECD), was optimized with respect to the applied potential, sample and reagent volume, and flow rate to the detector. Gallic acid was used as the standard antioxidant and the capacity was reported as gallic acid equivalent (GAE) unit. TAC measurements of ginger infusions at the optimum condition were performed using the proposed technique and also with the classical batch spectrophotometric ABTS assay. TAC values obtained from our method and the standard method are in good agreement (r 2 = 0.956). The SI-amperometric technique provided satisfactory precision (4.11% RSD) with rapid sample throughput (40 samples h −1). Also using this method, the consumption of the expensive ABTS reagent was greatly reduced.
Pure and Applied Chemistry, 2012
The evolution of an entirely green analytical system for industrial quality control of carbonated... more The evolution of an entirely green analytical system for industrial quality control of carbonated drinks is described. The developed flow system is capable of providing analytical data of the dissolved CO2, sucrose, and color of a sample consecutively in real-time. The system has been carefully designed on the basis of “reagent-free”, meaning that no added chemicals are required for the analysis. The system first vaporizes CO2 from the soft drink in a gas–liquid separation chamber, with a channel for a flow of pure water as the CO2 acceptor. The dissolved CO2 alters the conductivity of the water stream, which is directly related to the concentration of CO2 in the soft drink. The sucrose content is measured based on the “schlieren effect”, the sample plug flows out of the vaporization chamber into a colorimeter with a near-infrared/light-emitting diode (NIR/LED) as light source. The schlieren effect arises at the boundary of pure water and soft drink with refraction of light in propo...
Colorimetric Sensor Using Silver Nanoparticles for Determination of Hydrogen Peroxide Based on a Flow Injection System
Journal of Nanoelectronics and Optoelectronics, 2013
ABSTRACT In this work, a colorimetric probe using a flow injection (FI) system and silver nanopar... more ABSTRACT In this work, a colorimetric probe using a flow injection (FI) system and silver nanoparticles (AgNPs) was developed for determination of hydrogen peroxide (H2O2) concentration. AgNPs have catalytic ability for decomposition of H2O2, producing silver ions and superoxide. The reaction mechanism of H2O2 and AgNPs at various concentrations is described. H2O2 concentration was quantified by monitoring decrease in AgNPs surface plasmon resonance during the decomposition reaction. Under the optimum condition, the detection limit for H2O2 was 0.6 mg/l. The flow system developed in this study provided good precision of analysis (relative standard deviation = 2.97%) with high throughput (18 samples/h). This method was successfully applied to analysis of H2O2 in pharmaceutical and household products. Therefore, the method is feasible for on-line monitoring H2O2 in manufacturing process quality control.
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Papers by saowapak teerasong