A sensitive and rapid method for the determination of protein by the resonance Rayleigh light-scattering technique with Pyrogallol Red

Optimization of 25% Sulfosalicylic Acid Protein-to-Creatinine Ratio for Screening of Low-Grade Proteinuria

Proteinuria is an important prognostic marker in the diagnosis and management of kidney diseases. Sulfosalicylic acid method (SSA) is a simple, low cost, qualitative test, widely used to assess proteinuria. The aim of this study was to optimize SSA test as a quantitative screening tool to assess proteinuria at lower excretory levels which would facilitate the screening and early diagnosis of renal impairment using protein-to-creatinine ratio (PCR). The study was conducted in two phases. In phase I, optimum SSA percentage to detect low-grade proteinuria was selected by comparing the performance of 3%, 6%, and 25% SSA methods in manual spectrophotometric analysis. In phase II, clinical applicability of the optimized method was evaluated using retained urine samples of patients with chronic kidney disease (CKD) assessed for urine protein by the pyrogallol red (PGR) method in a tertiary care hospital in Sri Lanka. Optimized 25% SSA protein-to-creatinine ratio (PCR) was compared with PGR PCR and albumin-to-creatinine ratio (ACR). Sensitivity, specificity, degree of agreement, correlation, and diagnostic accuracy were evaluated. Turbidimetric analysis using 25% SSA was linear in the range 3–50 mg/dL giving the highest analytical sensitivity. The test yielded a sensitivity of 86.5% and specificity of 96.5% and a degree of agreement of 5 mg/dL with the PGR method. Optimal cut-off for 25% SSA PCR in receiver operating characteristic analysis was 166 mg/g. Spearman's correlation coefficient for 25% SSA PCR versus ACR was r = 0.823, p < 0.0001, and for 25% SSA PCR versus PGR PCR was r = 0.913, p < 0.0001. The 25% SSA PCR has a sensitivity of 92% against ACR, the current prognostic marker for proteinuria in patients with CKD. The 25% SSA test is a simple method, and it performs satisfactorily as a screening test with a cut-off for PCR optimized at 166 mg/g. The test merits further evaluation due to its low cost.

The triple-wavelength overlapping resonance Rayleigh scattering method and the fluorescence quenching method for the determination of chitooligosaccharides using trisodium-8-hydroxypyrene-1,3,6-trisulfonate as a probe

In this assay, the triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method and the fluorescence quenching method for the quantitative detection of chitooligosaccharides (COS) were developed. In the weakly Britton-Robinson buffer solution, COS interacted with Trisodium-8-hydroxypyrene-1,3,6-trisulfonate (HPTS) to form an ion-association complex of HPTS-COS, which increased the RRS intensities at 321 nm, 430 nm and 511 nm and decreased the fluorescence intensities of the system at 512 nm. And the changes in the intensities of both methods were related to the changes in the concentration of COS. Moreover, for the TWO-RRS method, OP-10 made the RRS intensities increased stronger, finally, the three peaks' total was linear to the concentration of COS in the range of 1.00-8.00 μg/mL and the limit of detection (LOD) was 0.247 μg/mL, and for the fluorescence quenching method, the linear range was 0.50-3.50 μg/mL with the LOD of 0.108 μg/mL. Based on these, two new and fast spectral methods with high sensitivity and simplicity for the determination of trace COS had been established. The generation mechanism of the TWO-RRS and the fluorescence quenching was studied. At the same time, the two methods were applied to the determination of COS in health products with satisfactory results.

Study on Brilliant Blue-chitosan System by Dual-wavelength Overlapping Resonance Rayleigh Scattering Method and its Analytical Applications

The method was presented for the sensitive and selective determination of chitosan (CTS) in health products with Brilliant Blue (BB) as a probe, based on dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS). In weakly acidic buffer solution, the binding of CTS and BB could result in the RRS intensities getting enhanced significantly at RRS peaks of 344nm and 452nm, and the scattering intensities of the two peaks were proportional to the concentration of CTS within a certain range. When the RRS intensities of the two wavelengths were superposed, the results showed higher sensitivity. Under the optimum experimental conditions, the total of the two increased RRS intensities was linear to the CTS concentration in the range of 0.02-1.80μg/mL and the limit of detection (LOD) was 7.45ng/mL. In this work, the optimum conditions and the effects of some foreign substances were studied. Accordingly, the new method based on DWO-RRS for the determination of CTS was developed. In addition, the effect of the molecular weight and the deacetylation degree between different chitosan molecules was discussed. Finally, this assay was applied to determine the concentration of CTS in health products with satisfactory results.

Synthesis, surface properties and temperature dependence of phase separation of DSPE chains in ethanol solutions

The surface properties, phase separation processes and kinetics of a DSPE/ethanol solution were investigated.

Resonance light scattering method for the determination of DNA with cationic methacrylate based polymer nanoparticle probes

Narrowly distributed cationic poly (methyl methacrylate-co-diacetone acrylamide) (P(MMA-DAAM)) nanoparticles were successfully prepared by microemulsion polymerization. Photon correlation spectrometer (PCS) measurement and transmission electron microscope (TEM) observation revealed that z-average particle size of P(MMA-DAAM) is ∼27.5 nm. It was found that these cationic nanoparticles interact with DNA through electrostatic interaction to form P(MMA-DAAM)-DNA complex, which significantly enhances the resonance light scattering (RLS) signal. Therefore, a novel method using this polymer nanoparticle as a new probe for the detection of DNA by RLS technique is developed in this paper. The results showed this method is very convenient, sensitive, and reproducible.

Determination of protein by resonance light scattering technique using dithiothreitol-sodium dodecylbenzene sulphonate as probe

The resonance light scattering (RLS) spectra of bovine serum albumin (BSA)-dithiothreitol (DTT)-sodium dodecylbenzene sulphonate (SDBS) and its analytical application were investigated. The RLS intensity of this system can be effectively enhanced in the presence of BSA. Based on the enhanced RLS intensity, a simple assay for BSA was developed. The experimental results indicate that the enhanced RLS intensity is proportional to the concentration of BSA in the range from 1.0 x 10(-8) to 7.5 x 10(-7) mol L(-1) with the determination limit of 5.0 x 10(-9) mol L(-1). The effects of pH, concentration of SDBS and DTT on the RLS enhancement were discussed. Most metal ions have little interference on the determination of BSA. Some synthetic and real samples were analyzed, and the results obtained were in good agreement with those obtained by Bradford method.

Determination of proteins at nanogram levels with Bordeaux red based on the enhancement of resonance light scattering

A simple, sensitive and selective method was proposed for the determination of proteins by using a resonance light scattering technique. The weak resonance light scattering (RLS) of Bordeaux red (BR) can be enhanced greatly in the pH range 3.87-3.96 by the addition of micro amounts of proteins, resulting in four characteristic peaks in the wavelength range 250-600 nm. At the maximal wavelength of 363 nm, the enhanced RLS is proportional to the concentration of proteins in the range 0.12-10.8 microg ml-1 for bovine serum albumin (BSA) and 0.24-18.0 microg ml-1 for human serum albumin (HSA). The detection limits were 40.0 and 52.9 ng ml-1 for BSA and HSA, respectively. The present method has been applied to the determination of total proteins in human serum, urine and saliva samples. The obtained results are in good agreement with those obtained by the Bradford method with relative standard deviations (R.S.D.) of 0.9-2.3%.

Studies on the interaction of protein with acid chrome blue K by electrochemical method and its analytical application

An electrochemical investigation on the interaction of acid chrome blue K (ACBK) with protein on the mercury electrode with different electrochemical methods such as cyclic voltammetry and linear sweep voltammetry was reported in this paper. In pH 3.0 Britton-Robinson (B-R) buffer solution, ACBK has an irreversible voltammetric reductive peak at -0.23 V (vs. SCE). The addition of human serum albumin (HSA) into the ACBK solution resulted in the decrease of reductive peak currents without the change of the peak potential and no new peaks appeared on the cyclic voltammogram. In the absence and presence of HSA, the electrochemical parameters such as the formal potential E0, the electrode reaction standard rate constant k(s) and the charge transfer coefficient alpha of the interaction system were calculated and the results showed that there were no significant changes between each other. Thus, the interaction of ACBK with protein forms an electro-inactive supramolecular bio-complex, which induces the decrease of the free concentration of ACBK in the reaction solution, and the decrease of the reductive peak current of ACBK. The binding constant and the binding ratio are calculated as 1.29 x 10(8) and 1:2, respectively, and the interaction mechanism is discussed. Based on the binding reaction, this new electrochemical method is further applied to the determination of HSA with the linear range from 3.0-20.0 mg/L and the linear regression equation as deltaIp"(nA) = 10.08 + 19.90 C (mg/L). This method was further applied to determinate the content of protein in the healthy human serum samples with the results in good agreement with the traditional Coomassie brilliant blue G-250 spectrophotometric method.

Pharmacokinetic detection of penicillin excreted in urine using a totally internally reflected resonance light scattering technique with cetyltrimethylammonium bromide

A quantitative analysis method for penicillins including ampicillin (AmP), benzyl penicillin (BP), oxacillin (OA) and amoxycillin (AmO) is proposed that makes use of the totally internally reflected resonance light scattering (TIR-RLS) signal from the penicillin at the H2O/CCl4 interface in the presence of cetyltrimethylammonium bromide (CTMAB), and enables the pharmacokinetics of penicillin taken orally and excreted through urine to be monitored. Penicillin is coadsorbed with CTMAB at the H2O/CCl4 interface in neutral solution, resulting in the formation of ion associates that display greatly enhanced TIR-RLS signals (maximum at 368-372 nm). This enhanced TIR-RLS intensity was found to be proportional to the penicillin concentration over the range 0.2 x 10(-6) to 2.2 x 10(-6) mol L(-1), with limits of determination (3sigma) of 5.0 x 10(-8) to 7.0 x 10(-8) mol L(-1). Pharmacokinetics studies performed using the present method show that the excretion of orally-taken ampicillin through urine has a half-time of 1.05 h and an excremental quantum over 8 h of 49.3%, respectively.

Nanogold plasmon resonance-based glucose sensing. 2. Wavelength-ratiometric resonance light scattering

Gold colloids are well known to display strong plasmon absorption bands due to electron oscillations induced by the incident light. When the colloids are in proximity, the plasmon absorption bands are often perturbed. This has enabled us recently to successfully develop a glucose sensing platform based on the disassociation of dextran-coated gold colloids, cross-linked with Con A, by glucose. However, a much more useful and simpler property of gold colloids, which has been ill explored with regard to sensing, is their ability to efficiently scatter excitation light. We have found that our nanogold sensing aggregates are indeed efficient light scatters around the nanogold plasmon absorption band. By measuring the ratio of scattered light intensities at two different arbitrary wavelengths, 560 and 680 nm, glucose concentrations can be readily determined from a few millimolar up to approximately 60 mM, using a simple white light LED and detection system. Further, by measuring the ratio of the scattered intensities, this sensing approach is independent of the total sensing aggregate concentration and the excitation and detection instrumentation fluctuations or drifts. This simplistic and low-cost approach to glucose sensing, coupled with the sensing aggreagates' ability to scatter red light, suggests the potential use of these aggregates for use in physiological transdermal glucose monitoring, either for implantable skin sensors or glucose sensing tattoos (discussed later).

Resonance Rayleigh scattering study of interaction of heparin with some cationic surfactants and their analytical application

Binding of heparin with a cationic surfactant such as cetyldimethyl benzylammonium chloride (CDBAC), tetradecyldimethyl benzylammonium chloride (Zeph), cetylpyridinium bromide (CPB), tetradecane pyridinium bromide (TPB) and cetyltrimethylammonium bromide (CTAB) in a near-neutral medium can result in a significant enhancement of resonance Rayleigh scattering (RRS) intensities. The results showed that the reaction conditions and RRS spectral characteristics of these reactions are similar, but their sensitivities are obviously different. Among them, the sensitivity of CDBAC with an aryl and large molecular weight is the highest, while that of CTAB without aryl and with small molecular weight is the lowest. The detection limit for heparin of the former is 11 ng ml(-1) while that of the latter is 33 ng ml(-1). The method has better selectivity and was applied to the determination of trace amounts of heparin in sodium heparin injection samples with satisfactory results. Furthermore, it is discovered that the RRS intensity is related to the structure and molecular weight of the cationic surfactant.

Resonance light scattering technique for the determination of protein with rutin and cetylpyridine bromide system

A new resonance light scattering (RLS) assay of protein is presented. In Tris-NaOH (pH = 10.93) buffer, the RLS of rutin-cetylpyridine bromide (CPB) system can be greatly enhanced by protein, including bovine serum albumin (BSA) and human serum albumin (HSA). The enhanced RLS intensities are in proportion to the concentration of proteins in the range of 5 x 10(-9) to 2.5 x 10(-6) g ml(-1) for BSA and 2.5 x 10(-8) to 3.5 x 10(-6) g ml(-1) for HSA. The detection limits (S/N = 3) are 3.0 ng ml(-1) for BSA and 10.0 ng ml(-1) for HSA. Samples are determined satisfactorily.

Proton T1 and T2 relaxivities of serum proteins

In the present study, T(1) and T(2) of phantoms containing serum sets with varying amounts of proteins, serum samples with certain amounts of proteins, serum diluted by distilled water, and serum treated with iron were measured. In addition, T(1) and T(2) of phantoms containing normal serum, diluted serum, and albumin-doped serum were also measured. Relaxation rates were plotted versus protein concentrations. The slope of relation was taken as relaxivity. The T(1) relaxivities of proteins were ranged from 0.035 to 0.080 s(-1)(g/dl)(-1), whereas T(2) relaxivities were ranged from 0.24 to 0.68 s(-1)(g/dl)(-1). The T(1) and T(2) relaxivities of transferrin iron were 2.40 and 2.60 mM(-1)s(-1), respectively. The contributions of diamagnetic proteins and transferrin iron to the relaxation rate of serum were also calculated for each of diluted serum, normal and albumin-doped serum. The contributions and the average TP relaxivities(calculated by using individual relaxivities and the ratios of protein fractions in TP) were used for TP calculations. The agreement between the calculated TP and TP by autoanalyzer and also the agreement between average TP relaxivities and the TP relaxivities determined from dilution experiments show that the data of relaxivities are reliable. The results suggest that individual protein relaxivities explain the influence of serum TP composition on T(1) and T(2) relaxation times.

Frequency doubling scattering and second-order scattering spectra of phosphato-molybdate heteropoly acid-protein system and their analytical application

In the sulfuric acid medium, the reaction of heteropoly compounds with proteins could result in the enhancement of frequency doubling scattering (FDS) and second-order scattering (SOS). Based on the characteristic, a novel method for the determination of trace amounts of protein by using the FDS and SOS method has been developed. Their maximum scattering wavelengths, lambda(ex)/lambda(em), appear at 940/470 nm for FDS and 350/700 nm for SOS, respectively. In a certain range, the concentration of proteins is directly proportional to the enhanced intensity of FDS and SOS. The suitable reaction conditions, affecting factors as well as the influence of some coexisiting substances were investigated. The methods exhibited high sensitivity, and the detection limits were in the range of 8.6-39.3 ng ml(-1) depending on different methods. The method had good selectivity, and was applied to the determination of protein in synthetic samples and practical samples with satisfactory results.

Resonance light scattering spectroscopy study of interaction between gold colloid and thiamazole and its analytical application

In this paper, we used resonance light scattering (RLS) spectroscopy to study the interaction between thiol-containing pharmaceutical-thiamazole and gold colloid. At pH 5.2, the resonance light scattering spectrum of gold nanoparticles has a maximum peak at 555 nm and the RLS intensity is enhanced by trace amount of thiamazole due to the interaction between thiamazole and gold colloid. The binding of colloidal gold to thiamazole results in ligand-induced aggregation of colloidal gold, which was characterized by RLS spectrum, ultraviolet-visible (UV-Vis) spectrum, and transmission electron microscopy (TEM). Based upon the study, we proposed a highly sensitive, gold colloid-based assay using RLS spectrum to detect pharmaceuticals for the first time. The mechanism of binding interaction between Au colloid and thiamazole was also discussed.

Direct quantification of human serum albumin in human blood serum without separation of gamma-globulin by the total internal reflected resonance light scattering of thorium-sodium dodecylbenzene sulfonate at water/tetrachloromethane interface

A direct quantification of human serum albumin (HSA) in blood serum samples without separation is proposed based on the measurements of total internal reflected resonance light scattering (TIR-RLS) at water/tetrachloromethane (H(2)O/CCl(4)) interfaces. In the pH range of 6.37-6.59, the coadsorption of the binary complex of HSA-Th(IV) with sodium dodecylbenzene sulfonate occurs at the H(2)O/CCl(4) interface, forming an amphiphilic layer and displaying greatly enhanced TIR-RLS signals with the maximum peak located at 340-370 nm. The enhanced TIR-RLS intensity is in proportion to the HSA concentration in the range 0.15-1.0 micro gml(-1). The limit of detection is 14.4 ngml(-1). The contents of HSA in blood serum samples were determined with the recovery of 97.1-102.3% and RSD of 0.6-2.9%, which are identical to those obtained according to the spectrofluorimetric method using chrome azurol S.