Concentration Of Thioglycolic Acid Research Articles

Effect of Zn/S/TGA concentration on the stability and optical properties of TGA capped ZnS quantum dots synthesized via one pot aqueous synthesis method

Aqueous ZnS quantum dots (QDs) were synthesised via a facile, cost-effective one-pot synthesis method in the ambient environment. To achieve most favourable ratios of thioglycolic acid (TGA):zinc (Zn):sulphide (S), the concentration optimisation by optical spectra (COOS) method was adopted. The x-ray diffraction (XRD) spectra confirmed the zinc-blende (cubic) phase of ZnS quantum dots (QDs), and Scherrer’s method determined that on average, the QDs exhibit a size of 2 nm. The Fourier-transform infrared spectroscopy (FTIR) study shows that characteristic peaks are consistent with the vibrational modes of the TGA ligands, confirming the capping. The quantum dots (QDs) synthesised displayed a significant effect of quantum confinement with blue shift in absorption peaks, compared with bulk ZnS absorption peak. Interestingly, on increasing the concentration of TGA, it resulted in red shift at the absorption edge, shifting from 300 nm to 314 nm. On the other hand, increasing the concentration of cation Zn and anion S ratio led to a blue shift, ranging from 315 to 295 nm, and a red shift, ranging from 280–320 nm, at absorption edges respectively. A prominent emission peak appeared at 428 nm. The application of Brus equation allowed estimating the size of the quantum dots (QDs) to be within the range of 2 to 2.7 nm, which correlated well with the Bohr’s radius of ZnS. This favourable property proposes the use of QDs in various optoelectronic devices.

Optimization of CdS nanorod synthesis via reflux method

CdS nanorods were successfully synthesized via a reflux method with the assistance of thioglycolic acid (TGA) and subsequent thermal annealing. The effects of TGA concentration, pH, reaction time, and annealing temperature on the CdS growth process were studied. CdS fabricated with 5 mL of TGA for 36 h exhibited high-density nanorods with an average-length–width of 1.54–0.10 µm and a wurtzite phase. CdS nanorods annealed at 400 °C for 1 h provided the best crystalline structure and morphology quality. Furthermore, they demonstrated visible light emissions and pronounced Raman phonon coupling. Our simple and facile synthesis approach holds great potential for various applications.

Molecular Imprinting Using a Functional Chain Transfer Agent.

This study demonstrates the feasibility of molecular imprinting using a functional chain transfer agent sans a functional monomer. Ethylene glycol dimethacrylate (EGDMA)-based MIPs were synthesised in the presence of thioglycolic acid (TGA) possessing a carboxylic acid group, capable of interacting with the chosen test template R,S-(±)-propranolol (PNL) and a labile S-H bond to facilitate an efficient chain transfer reaction. Quantitative 1H NMR measurements showed high PNL and TGA incorporation within the MIP, indicating an efficient chain transfer process and a favourable interaction between PNL and TGA. TGA-50, with the lowest amount of CTA, showed the largest imprinting effect and an imprinting factor (IF) of 2.1. The addition of MAA to the formulation improved the binding capacity of PNL to the MIP but also increased NIP binding, resulting in a slightly decreased IF of 1.5. The Kd for the high-affinity sites of the TGA/MAA MIP were found to be two times lower (10 ± 1 μM) than that for the high-affinity sites of the TGA-only MIPs, suggesting that the incorporation of the functional monomer MAA increases the affinity towards the PNL template. Selectivity studies, cross-reactivity as well as binary competitive and displacement assays showed the TGA-based MIPs to be highly selective towards PNL against pindolol and slightly competitive against atenolol. The morphologies of the polymers were shown to be affected by the concentration of the TGA, transforming into discrete macrospheres (from small aggregates) at a higher TGA concentration.

Surface-Bonding-Enhanced Self-Co-Reactant Electrogenerated Chemiluminescence for Sensitive and Selective Detection of Thioglycolic Acid in Cosmetics.

Thioglycolic acid (TGA) is an organic compound widely used in cosmetics that cause a variety of health problems when overexposed to it. So far many attempts have been made to develop methods for TGA detection, but most of them need sophisticated instrumentations and are a little bit complicated. Therefore, a simple, cheap and sensitive detection method of TGA is highly desired. Herein, we demonstrated for the first time an Au-S bonding amplified, highly sensitive electrochemiluminescence (ECL) sensing method for TGA detection using tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)3 2+ ) as a luminophore and TGA as a self-co-reactant, via an anodic reaction at the Au electrode surface. Due to different molecular coordination environments of the TGA at the electrode surface, the ECL signal intensity of the developed ECL system gives much higher ECL signal in borate buffer than phosphate buffer of the same pH. Under the optimized experimental conditions, the ECL intensity has a direct relationship with the concentration of TGA in the range of 0.03 μM to 300 μM and a limit of detection of 0.013 μM (3σ/m). The reported ECL system has further been applied for the detection of TGA in cosmetics with acceptable recoveries.

Thioglycolic acid-modified AuNPs as a colorimetric sensor for the rapid determination of the pesticide chlorpyrifos.

Herein, we report the preparation of a gold nanoparticle-thioglycolic acid (TGA@AuNP) suspension for the label-free colorimetric detection of the organophosphorus pesticide chlorpyrifos. This colorimetric sensor was synthesized by a one-pot method, providing thioglycolic acid (TGA)-modified gold nanoparticles with a negatively charged surface. The formation of TGA@AuNPs was confirmed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and dynamic light scattering (DLS). In addition, chlorpyrifos was quantitatively determined by UV-vis spectrophotometry. The modification time, TGA concentration, pH, incubation time, temperature, ionic strength, and interference of other pesticides were also investigated. The synthesized TGA@AuNP colorimetric sensor possesses a detection limit as low as 20 μg L-1 and a selective sensing response, and the detection time is less than 2 minutes. In addition, this method can also be applied to detect various practical samples in life, such as environmental water samples and tea.

Poloxamer 407 Based Gel Formulations for Transungual Delivery of Hydrophobic Drugs: Selection and Optimization of Potential Additives.

The current study aimed to develop poloxamer 407 (P407) gel for transungual delivery of antifungal hydrophobic drugs with sufficient gel strength and drug loading. Gel strength and drug loading of P407 gel was improved by use of functional additives. Hydration enhancement effect was used to select optimum nail penetration enhancer. Face-centered central composite design (FCCCD) was used to observe the effect of the selected penetration enhancer (thioglycolic acid (TGA)) and cosolvent (ethanol) on gelation behavior to develop formulation with enough loading of hydrophobic drug, i.e., terbinafine HCl (TBN), and its permeation across the nail plate without compromising on gel strength. It was observed that increasing concentration of P407 and TGA significantly reduced gelation temperature and enhanced the gel strength of P407 gel and can be used to improve P407 gel strength. Under the scanning electron microscope, the significant effect of TGA as an ungual penetration enhancer was observed on the morphology of the nail plate. Optimized P407 gel prepared with modified cold method showed a gelation temperature of 8.7 ± 0.16 °C, gel strength of 122 ± 7.5 s and drug loading of 1.2% w/w, which was four times more than the drug loading in the gels prepared with conventional cold method. Rheological behavior was pseudoplastic with 47.75 ± 3.48% of gel erosion after 12 washings and 67.21 ± 2.16% of drug release after 12 h. A cumulative amount of TBN permeated from P407 gel with and without PE after 24 h was 27.30 ± 4.18 and 16.69 ± 2.31 µg/cm2, respectively. Thioglycolic acid can be used as a nail penetration enhancer without the chemical modification or addition of extra additives while retaining the gel strength. Water miscible cosolvents with moderate evaporability such as ethanol, can be incorporated to P407 gel by minor modification in method of preparation to load the required dose of hydrophobic drugs. Developed P407 gel formulation with sufficient gel strength and drug loading will be a promising carrier for transungual delivery of hydrophobic antifungal agents.

Thiolated sodium alginate conjugates for mucoadhesive and controlled release behavior of metformin microspheres

The absorption of BCS III drugs can be improved by inhibiting the P-glycoprotein (P-gp) efflux and by increasing the mucoadhesion of natural polymers. In the present study, an esterification of sodium alginate (SA) with thioglycolic acid (TGA) was applied for the preparation of thiolated sodium alginate (TSA). The Ellman's test was applied to quantify the thiol group and a di-sulphide bond test was performed to confirm any SS linkages. The FTIR, DSC, XRD, 1H NMR and charring point determinations were confirmed the thiol group of TSA. The gel like rheological properties with porcine mucous was confirmed by viscoelasticity properties and the mucoadhesion with the rabbit intestine was carried out after compression of 30 mg tablets of TSA. The content of thiol group was in the range of 320–730 μmoL/g of the polymer. The FTIR spectrum showed a characteristic peak of sulfhydryl group at 2557 cm−1 in TSA and the reduction of the charring point from 220 °C to 178 °C was confirmed the thiolation of TSA. A direct relationship of mucoadhesion and swelling was observed with the concentration of TGA and SA, respectively. The prepared microspheres were 2–7 μm in size, excellent rheological properties and non-fickian drug release behavior was observed.

Modified Poly(T-Butyl Methacrylate) as a Doxorubicin Carrier for Targeted Delivery

Poly(t-butyl methacrylate) (PTBMA) was selected as a doxorubicin carrier for targeted delivery because it can hydrolyze to form water-soluble polymers. A chain-transfer reaction with thioglycolic acid was used. The thioglycolic acid concentration was 1 mass%, at which a polymer with the optimal biocompatibility (molecular mass ~12 kDa, polydispersion index Mw/Mn ≈ 1.5) was obtained. The polymer was chemically modified by a folate vector. The resulting polymer was converted via acid hydrolysis into a water-soluble copolymer. Then, a conjugate of doxorubicin (DOX) with the copolymer of t-butyl methacrylate and methacrylic acid modified by the folate vector on the terminal carboxylates was prepared. The degree of DOX conjugation to the polymer was 62.7 ± 11.8%. DOX was released from the polymer system almost three times faster at pH 4.6 than at pH 7.4. The cytotoxicity of the polymer conjugate was 1.52 μM.

Synthesis of CdS Quantum Dots Using Direct Plasma Injection in Liquid Phase

In this work, we introduce a new method using non-equilibrium atmospheric pressure plasma jet (N-APPJ) for the synthesis of semiconductor quantum dots in liquid media with low power consumption at room temperature. In this method, the solution containing CdSO4, Na2S2O3 and thioglycolic acid (TGA) was treated by N-APPJ. Firstly, the key role of plasma applied voltage on the power consumption and the produced plasma reactive species was considered. We then continue to demonstrate that the optical properties such as absorption and photoluminescence of cadmium sulfide quantum dots (QDs) can carefully be controlled with the plasma parameters. Here, the effects of two major plasma parameters such as the plasma applied voltage and treatment time on the size of CdS QDs were investigated. The size of nanoparticles increases with the increase of the voltage and treatment time. It was also displayed that the change of the concentration of Na2S2O3 and TGA in the solution had no significant effect on the size of QDs in plasma method. Finally, X-ray diffraction, X-ray fluorescence spectrometry and transmission electron microscopy were employed to determine the composition, size and crystallinity of prepared CdS QDs.

Concentration-dependent optical properties of TGA stabilized CdTe Quantum dots synthesized via the single injection hydrothermal method in the ambient environment

Thioglycolic acid (TGA) stabilized aqueous CdTe Quantum dots (QDs) were synthesized using a facile, cost efficient Single Injection Hydrothermal (SIH) method. The complete preparation of precursors and growth of QDs was carried out in the ambient environment without inter gas protection. The Cadmium and Tellurium precursors were prepared from cadmium nitrate and elemental tellurium powder with sodium borohydride as reducing agent respectively. A systematic investigation was carried out in order to study the effect of 0.04M and 0.08M TGA concentration on ease synthesis, stability and size-tunable optical absorbance, bandgap, photoluminescence (PL) and Quantum yield (QY) of CdTe QDs. The Structure of QDs was verified by XRD and optical properties by absorbance and PL spectra. Experimental results revealed that the 0.08M TGA QDs possess good chemical and optical stability with high luminescence and decent QY, ready to use in optoelectronics, photovoltaic and biological application.

Simple and Rapid Quantitative Determination of Thiol-Containing Toxicants Using Silver Nanoparticles as an Affinity Probe

A rapid and low-cost nano-drop spectrophotometric method using citrate-modified silver nanoparticles (Ag NPs) for the determination of thiol-containing toxicants was developed. The introduction of thioglycolic acid (TGA) and thiourea (TU) reduced the overall surface charge of Ag NPs, resulting in aggregation of Ag NPs, and a colorimetric response that was individually correlated with the concentration of TGA and TU. Under optimum experimental conditions, the maximum molar absorptivity values for TGA and TU were 1.04 × 105 and 2.13 × 105 L × mol–1 × cm–1, respectively, at λmax of 415 nm. The linear range used was 0.5–2.5 mg/L for TGA, and 0.3–1.5 mg/L for TU. The detection limits (3S) and % relative standard deviation (RSD) for the method were found to be 3 ppb, 2 ppb, and ±1.13%, ±0.96% for TGA and TU, respectively. This new chromogenic method provided a facile and sensitive scheme for the determination of TGA and TU, and could be applied for the determination of thiol-containing biomolecules. This scheme was tested for the analysis of real samples such as urine, blood, and environmental samples.

The relationship between photoluminescence (PL) decay and crystal growth kinetics in thioglycolic acid (TGA) capped CdTe quantum dots (QDs).

The PL lifetime optimization of CdTe QDs capped with TGA has yet to be understood from a perspective of growth kinetics. In this work, the growth kinetics and PL properties of CdTe QDs growing in aqueous solutions of two TGA concentrations, 0 mM and 57 mM, were systematically investigated using UV, TEM, and PL methods. CdTe QDs in 0 mM TGA solution were found to follow the mixed OA (Oriented Attachment)-OR (Ostwald Ripening) growth kinetics. The PL peaks experienced a red-shift with almost unchanged intensity and the PL lifetimes increased gradually. In 57 mM TGA solution, the QDs followed the OA dominated growth mechanism. The PL peak broadened greatly with a red-shift and its intensity decreased significantly. The PL lifetime increased much higher than that in 0 mM TGA solution. Based on the different growth kinetic models of the two systems, we suggest that in the low (0 mM) TGA solution, the increased surface defects induced by TGA desorption and the existence of partial internal defects caused by OA growth were the main reasons for the gradual increase of PL lifetime, while in high (57 mM) TGA solution, the increase of PL lifetime was ascribed to the abundant internal defects produced by OA collision. Finally, kinetic data showed the effect of the TGA concentration on crystal growth and PL lifetime of CdTe QDs. The results might provide guidance for understanding the mechanism behind the phenomena of ligand-related PL properties.

Kinetics and Mechanism of the Interaction of Di-μ-hydroxobis(1,10-phenanthroline)dipalladium(II) Perchlorate with Thioglycolic Acid and Glutathione in Aqueous Solution

The kinetics of interaction between di-μ-hydroxobis(1,10-phenanthroline)dipalladium(II) perchlorate and thioglycolic acid and with glutathione has been studied spectrophotometrically in aqueous medium as a function of the complex concentration as well as the ligand concentrations, pH, and temperature at constant ionic strength. The observed pseudo-first-order rate constants k obs (s−1) obeyed the equation k obs = k 1[Nu] (Nu = nucleophile). At pH = 6.5, the interaction with thioglycolic acid shows two distinct consecutive steps and both steps are dependent on the concentration of thioglycolic acid. The rate constants for the process are: k 1 ≈ 10−5 s−1 and k 2 ≈ 10−3 dm3 · mol−1 · s−1. The association equilibrium constant (K E) for the outer sphere complex formation has been evaluated together with the rate constants for the two subsequent steps. The other bio-active ligand, glutathione, showed a single step reaction depending on [ligand] with a second-order anation rate constant: the 102 (k 2) values are (61.72, 79.20, 109.24 and 154.33) dm3 · mol−1 · s−1 at 20, 25, 30 and 35 °C, respectively. On the basis of the kinetic observations and evaluated activation parameters, plausible associative mechanisms are proposed for both interaction processes.

Preparation of thiolated polyvinyl alcohol hydrogels

AbstractThe esterification reaction of polyvinyl alcohol (PVA) with thioglycolic acid (TGA) in the presence of sulfuric acid as a catalyst offers an attractive route to develop thiolated functional material. During esterification maximum thiol content of 3.9 mmol/g was achieved. It was observed that the esterification is significantly influenced by the reaction conditions, such as TGA concentration, reaction time, reaction temperature and reactant concentration. Sulfuric acid had considerable influence on the thiolation. The thiol content was found to increase with the reaction temperature but showed significant increase beyond 60°C. The swelling decreases with the increasing reaction temperature indicating the role of crosslinking during the thiolation at higher temperature. Suitable conditions for the modification of PVA via thiolation have been investigated. The involvment of thiol group in the PVA matrix was confirmed by ATR‐FTIR spectra. The micro analysis of sulfur in sample by EDX analysis showed the sulphur content of 3.7%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Star-shaped PbS nanocrystals prepared by hydrothermal process in the presence of thioglycolic acid

Nanocrystalline PbS with different morphologies and particle sizes was obtained via a simple hydrothermal reaction between Pb(NO3)2 and thioglycolic acid (TGA) at relatively low temperature. Products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence (PL) and Fourier transform infrared (FT-IR) spectroscopy. Depending on the reactant concentration and molar ratio of TGA to the lead nitrate, the morphologies of the PbS crystals varied and the crystals with shapes of nanoparticles, star-like dendrite and nanorods were obtained. The effect of reaction temperature and reaction time on the morphology and particle sizes of nanocrystalline PbS products has been investigated.

Effects of Thioglycolic Acid on Parthenogenetic Activation of Xenopus Oocytes

BackgroundExisting in Permanent-wave solutions (PWS), thioglycolic acid (TGA) is widely used in hairdressing industry for its contribution to hair styling. However, the toxicity of TGA, especially its reproductive toxicity, gradually calls the attention of more and more researchers.MethodIn this work, xenopus oocytes were pretreated with different concentration of TGA, and then activated by calcium ionophore A23187. During culture, the oocytes activation rates were taken note at different time after adding calcium ionophore A23187. At the end of the culture period, the nuclear status was detected under confocal microscope. In addition, some other samples were collected for Western-Blotting analysis.ResultTGA significantly inhibited the oocytes activation rate and pronuclear formation. It may be resulted from the inhibition of the degradation of p-ERK1, Mos and CyclinB2.ConclusionTGA inhibits in vitro parthenogenetic activation of xenopus oocytes with inhibited the degradation of proteins involved in mitogenic-activated protein kinase (MAPK) and maturation-promoting factor (MPF) pathways.

Determination of Thioglycolic Acid in Hair-Waving Products by Disposable Electrochemical Sensor Coupled with High-Performance Liquid Chromatography

A disposable electrochemical sensor coupled with high-performance liquid chromatography (HPLC) was developed for the determination of thioglycolic acid (TGA) in commercial hair-waving products. The quantitative determination of TGA was first investigated by using a preanodized (*) screen-printed carbon electrode (SPCE*). Because of the electrocatalytic effect of the SPCE*, the peak potential (Epa) was shifted less positively as the current magnitude increased. HPLC was used in this study to eliminate interference from the matrix of real samples. The effects of various parameters, such as preanodization potential, preanodization time, solution pH, detection potential, and mobile phase, were studied in detail. Under optimized conditions, the linear range for TGA is up to 20 ppm, correlation coefficient (r2) = 0.998, with a detection limit of 0.042 ppm (signal-to-noise ratio = 3). The practical application of the proposed method was demonstrated by the determination of TGA concentration in commercial hair-waving products.

Chemical Reactions Occurring in Curing Treatment for Permanent Hair Straightening Using Thioglycolic and Dithioglycolic Acids

A curing method for hair straightening has been practically applied for decade. The straightening process consists of three step reactions: reduction followed by washing, heat treatment and oxidation. Two different reduction systems were used: one is a system containing thioglycolic acid (TGA) only and the other is a bicomponet system containing TGA and dithiodiglycolic acid (DTDG). Reaction mechanism was proposed on the basis of amino acid analysis of the hair samples obtained at various treatment steps. New equilibrium reactions were assumed to be established in the reduced fiber after washing and we could explain successfully the experimental results. As far as TGA is used for the reduction, a sever problem for the damage of hair arises from the formation of the mixed disulfide groups. There were important findings on this subject that (1) when the TGA-only system was used, the mixed disulfide groups were formed in the fiber and the amount of the groups incorporated was dependent on the concentration of TGA, (2) in the heat-treatment step at 180°C for 3 sec, the mixed disulfide groups were wholly converted into the thiol groups of cysteine residues, and (3) when the bicomponent system was applied, only the thiol groups were linked to the protein chains even under a hot permanent conditions at 45°C for 15 min. The role of DTDG is not only a reduction-regulating agent, but also a thiol-reforming agent, in other words, DTDG acts as an anti-damaging agent.

Chemical method to enhance transungual transport and iontophoresis efficiency

Transungual transport is hindered by the inherent small effective pore size of the nail even when it is fully hydrated. The objectives of this study were to determine the effects of chemical enhancers thioglycolic acid (TGA), glycolic acid (GA), and urea (UR) on transungual transport and iontophoresis efficiency. In vitro passive and iontophoretic transport experiments of model permeants mannitol (MA), UR, and tetraethylammonium (TEA) ion across the fully hydrated, enhancer-treated and untreated human nail plates were performed in phosphate-buffered saline. The transport experiments consisted of several stages, alternating between passive and anodal iontophoretic transport at 0.1 mA. Nail water uptake experiments were conducted to determine the water content of the enhancer-treated nails. The effects of the enhancers on transungual electroosmosis were also evaluated. Nails treated with GA and UR did not show any transport enhancement. Treatment with TGA at 0.5 M enhanced passive and iontophoretic transungual transport of MA, UR, and TEA. Increasing the TGA concentration to 1.8 M did not further increase TEA iontophoresis efficiency. The effect of TGA on the nail plates was irreversible. The present study shows the possibility of using a chemical enhancer to reduce transport hindrance in the nail plate and thus enhance passive and iontophoretic transungual transport.

Electrocatalytic oxidation of thioglycolic acid at carbon paste electrode modified with cobalt phthalocyanine: application as a potentiometric sensor

The voltammetric behavior of thioglycolic acid (TGA) was studied at a carbon paste electrode modified with cobalt phthalocyanine (CoPc). The CoPc-modified electrode shows high electrocatalytic activity toward oxidation of TGA, lowering substantially the overpotential of anodic reaction. Results of the cyclic voltammetry show that TGA undergoes a two-step oxidation (each step with one electron) resulting the dimer of thiol. Enhancement of the rate of electron transfer results in a near-Nernstian behavior of modified electrode to the concentration of TGA and makes it as a suitable potentiometric sensor for the detection of this compound. This electrode shows a near-Nernstian response in a wide linear range of the concentration TGA (∼4 orders of magnitude). The modified electrode was used successfully for the determination of TGA and its salts in hair-treatment products and also in culture media. The modified electrode exhibited a fast response time (<10 s), very good stability, and had an extended lifetime.