Magnetic nanocomposite of anti-human IgG/COOH-multiwalled carbon nanotubes/Fe₃O₄ as a platform for electrochemical immunoassay

An electrochemical immunosensing method was developed based on a magnetic nanocomposite. The multiwalled carbon nanotubes (MWCNTs) were treated with nitric acid to produce carboxyl groups at the open ends. Then, Fe₃O₄ nanoparticles were deposited on COOH–MWCNTs by chemical coprecipitation of Fe²⁺ and Fe³⁺ salts in an alkaline solution. Goat anti-human IgG (anti-hIgG) was covalently attached to magnetic nanocomposite through amide bond formation between the carboxylic groups of MWCNTs and the amine groups of anti-hIgG. The prepared bio-nanocomposite was used for electrochemical sensing of human tetanus IgG (hIgG) as a model antigen. The anti-hIgG magnetic nanocomposite was fixed on the surface of a gold plate electrode using a permanent magnet. The hIgG was detected using horseradish peroxidase (HRP)-conjugated anti-hIgG in a sandwich model. Electrochemical detection of hIgG was carried out in the presence of H₂O₂ and KI as substrates of HRP. Using this method, hIgG was detected in a concentration range from 30 to 1000 ng ml^?1 with a correlation coefficient of 0.998 and a detection limit of 25 ng ml^?1 (signal/noise = 3). The designed immunosensor was stable for 1 month.     

An electrochemical immunosensor for digoxin using core–shell gold coated magnetic nanoparticles as labels

A simple, sensitive, and low-cost immunosensor was designed for the detection of digoxin through core–shell gold coated magnetic nanoparticles (Fe₃O₄-Au-NPs) as an electrochemical label. Having had such a large potential for a variety of applications, Fe₃O₄-Au-NPs have attracted a considerable attention and are actively investigated recently. Digoxin is a cardiac glycoside which, at high level, can indicate an increased risk of toxicity. This new competitive electrochemical immunosensor was developed based on antigen–antibody reaction employing antigen (Ag) labeled Fe₃O₄-Au-NPs and PVA modified screen-printed carbon electrode surface in order to detect the serum digoxin. The structures of Fe₃O₄-Au-NPs were studied by transmission electron microscopy, X-ray diffraction and Fourier transformed infrared spectroscopy. Cyclic voltammetry and differential pulse voltammetry (DPV) were employed to determine the physicochemical and electrochemical properties of immunosensor. DPV was employed for quantitative detection of digoxin in biological samples. The developed immunosensor was capable to detect digoxin in the range from 0.5 to 5 ng mL^?1, with a detection limit as low as 0.05 ng mL^?1. The proposed method represented acceptable reproducibility, stability, and reliability for the rapid detection of digoxin in serum samples.     

Kinetic approach of aflatoxin B1-acetylcholinesterase interaction: a tool for developing surface plasmon resonance biosensors

This work presents a kinetic approach of the interaction between acetylcholinesterase (AChE) from electric eel and aflatoxin B1 (AFB1) or its protein conjugate (e.g., AFB1–HRP [horseradish peroxidase]) in order to develop a simple and sensitive detection method of these compounds. The dissociation constant K_d of the AChE/AFB1–HRP interaction (0.4 μM) obtained with the surface plasmon resonance (SPR) technique is very close to the inhibition constant reported in amperometric assay (K_i = 0.35 μM), proving that the conjugation of AFB1 to a carrier protein does not significantly influence the affinity of AFB1 for AChE. Thus, the AChE/AFB1–HRP couple can be used as mimic system for the binding of AChE to other AFB1–protein adducts and further used for developing biosensors for AFB1 bound to plasma proteins. The immobilization protocol was designed to minimize the nonspecific adsorption on the self-assembled monolayer (SAM) functionalized surface of the SPR chip without an additional hydrophilic linker, whereas the interaction protocol was designed to mark out the possible occurrence of mass transport limitation (MTL) effects. The detection limits (LODs) were 0.008 μM for AFB1–HRP (2.5 ng ml^?1 AFB1) and 0.94 ng ml^?1 for AFB1 itself, which is lower than recently reported values in spectrophotometric and amperometric assays.     

Budesonide quantification by HPLC coupled to atmospheric pressure photoionization (APPI) tandem mass spectrometry. Application to a comparative systemic bioavailability of two budesonide formulations in healthy volunteers

In the present study, a novel, fast, sensitive and robust method to quantify budesonide in human plasma using 3-keto-desogestrel as the internal standard (IS) is described. The analyte and the IS were extracted from human plasma by liquid–liquid extraction (LLE) using ether. Extracted samples were analyzed by high performance liquid chromatography coupled to Atmospheric pressure photoionization tandem mass spectrometry (HPLC–APPI-MS/MS). Chromatography was performed isocratically on a C18, 5 μm analytical column. The temperature of the autosampler was kept at 6 °C and the run time was 4.00 min. A linear calibration curve over the range 7.5–1000 pg ml^?1 was obtained and the lowest concentration quantified was 7.5 pg ml^?1, demonstrating acceptable accuracy and precision. This analytical method was applied in a relative bioavailability study in order to compare a test budesonide 64 μg/dose nasal spray formulation vs. a reference 64 μg/dose nasal spray formulation (Budecort Aqua) in 48 volunteers of both sexes. The study was conducted in an open randomized two-period crossover design and with a one-week washout period. Plasma samples were obtained over a 14 h interval. Since the 90% CI for both C_max, AUC_last and AUC_0-inf were within the 80–125% interval proposed by the Food and Drug Administration and ANVISA, it was concluded that budesonide 64 μg/dose nasal spray was bioequivalent to Budecort Acqua^® 64 μg/dose nasal spray, according to both the rate and extent of absorption.     

Online immobilized enzyme microreactor for the glucose oxidase enzymolysis and enzyme inhibition assay

An online immobilized glucose oxidase (GOx) capillary microreactor was developed based on an enzymatic redox reaction with 1,4-benzoquinone as an acceptor of electrons, replacing the molecular oxygen typically used in a GOx reaction to achieve direct ultraviolet detection without derivation. A high efficiency of enzymolysis was obtained at 1 mg ml^?1 1,4-benzoquinone for 5 min of incubation at 25 °C, and baseline separation of the substrate and product could be achieved with a resolution of 3.85 by employing 20 mM phosphate buffer (pH 8.0) containing 40 mg ml^?1 sulfated β-cyclodextrin as an additive, a constant voltage of 15 kV, and a detection wavelength of 220 nm. In addition, an online enzyme inhibition study was performed on the immobilized GOx microreactor with metal ions Ag⁺ and Cu²⁺ used as model inhibitors. The results indicate that Ag⁺ (IC₅₀ = 69.16 μM) has a markedly higher inhibitory effect than Cu²⁺ (IC₅₀ = 1.33 mM). The protocol described can be applied in high-throughput screening of enzyme reactions and inhibitors.     

CDP-choline-induced contractions in the mouse gastric fundus through purinoceptors and Rho/Rho-kinase signalling

AimsThis study aimed to investigate the effects of cytidine-5′-diphosphocholine (CDP-choline), an endogenous lipid precursor, on the reactivity of the mouse gastric fundus and to determine the mechanism(s) mediating its effects.Main methodsPossible contractile effect of CDP-choline (10^? 5–10^? 2 M) was investigated in the absence and presence of a muscarinic receptor antagonist, atropine (3 × 10^? 6 M), an acetylcholine esterase inhibitor, physostigmine (10^? 6 M), a Na⁺ channel blocker, tetrodotoxin (TTX, 3 × 10^? 6 M), a Rho-kinase inhibitor, Y-27632 (10^? 5 M), a purinoceptor antagonist, suramin (2 × 10^? 4 M), a nitric oxide synthase inhibitor, N^G-nitro-L-arginine (L-NA, 3 × 10^? 4 M), a Ca²⁺ channel blocker, nifedipine (10^? 6 M), an α₇ nicotinic receptor antagonist, methyllycaconitine citrate (MLA, 10^? 6 M) and a G protein (G_i/o) inhibitor, pertussis toxin (PTX, 2 μg/ml). The metabolites of CDP-choline, namely choline (10^? 4–10^? 2 M), cytidine 5′-triphosphate (CTP, 10^? 5–10^? 2 M), cytidine (10^? 5–10^? 2 M) and cytidine monophosphate (CMP, 10^? 3–10^? 2 M) were also tested. Besides, phosphorylation of MYPT1, which indicates Rho-kinase activity, was also detected.Key findingsCDP-choline produced contractions in a concentration-dependent manner. The contractions were not affected by atropine, physostigmine, TTX, PTX, MLA or L-NA. However, Y-27632, suramin or nifedipine partly reduced these contractions. CDP-choline increased phosphorylation of MYPT1. Among CDP-choline metabolites, cytidine had no contractile effects. However, choline induced considerable contractions, which were sensitive to atropine. CMP and CTP had also contractile activity, comparable to that of CDP-choline.SignificanceThese results suggest that CDP-choline produced contraction through, at least in part, purinoceptors and Rho/Rho-kinase signalling in the mouse gastric fundus.     

Pseudo-enzymatic hydrolysis of 4-nitrophenyl acetate by human serum albumin: pH-dependence of rates of individual steps

Human serum albumin (HSA) displays esterase activity reflecting multiple irreversible chemical modifications rather than turnover. Here, kinetics of the pseudo-enzymatic hydrolysis of 4-nitrophenyl acetate (NphOAc) are reported. Under conditions where [HSA] ? 5×[NphOAc] and [NphOAc] ? 5×[HSA], the HSA-catalyzed hydrolysis of NphOAc is a first-order process for more than 95% of its course. From the dependence of the apparent rate constants k_app and k_obs on [HSA] and [NphOAc], respectively, values of K_s, k₊₂, and k₊₂/K_s were determined. Values of K_s, k₊₂, and k₊₂/K_s obtained at [HSA] ? 5×[NphOAc] and [NphOAc] ? 5×[HSA] are in good agreement, the deacylation step being rate limiting in catalysis. The pH-dependence of k₊₂/K_s, k₊₂, and K_s reflects the acidic pK_a shift of the Tyr411 catalytic residue from 9.0 ± 0.1 in the substrate-free HSA to 8.1 ± 0.1 in the HSA:NphOAc complex. Accordingly, diazepam inhibits competitively the HSA-catalyzed hydrolysis of NphOAc by binding to Tyr411.     

Optimization of Cd2+ removal by the cyanobacterium Synechocystis pevalekii using the response surface methodology

Response surface methodology (RSM) has been used to optimize the critical parameters responsible for higher Cd²⁺ removal by a unicellular cyanobacterium Synechocystis pevalekii. A three-level Box–Behnken factorial design was used to optimize pH, biomass and metal concentration for Cd²⁺ removal. A coefficient of determination (R²) value (0.99), model F-value (86.40) and its low p-value (F < 0.0001) along with lower value of coefficient of variation (5.61%) indicated the fitness of response surface quadratic model during the present study. At optimum pH (6.48), biomass concentration (0.25 mg protein ml^?1) and metal concentration (5 μg ml^?1) the model predicted 4.29 μg ml^?1 Cd²⁺ removal and experimentally, 4.27 μg ml^?1 Cd²⁺ removal was obtained.     

Determination of hippuric acid in human urine by ion chromatography with conductivity detection

A simple, rapid, precise and eco-friendly ion chromatography (IC) method for the determination of hippuric acid (HA) in human urine was proposed in this paper. The separation was carried out an anion exchange column with 2.0 mmol L^?1 Na₂CO₃ + 2.0 mmol L^?1 NaHCO₃ as mobile phase at the flow-rate 0.7 mL min^?1. A suppressed conductivity detector was used and the detection limit was 1.0 μg L^?1(S/N = 3) for hippuric acid. The analysis time for one run was 30 min under the optimized IC condition. The recovery of hippuric acid was 93.2–98.0% while the relative standard deviation (RSD) was 1.4–2.3% by seven measurements.     

Predictive modeling of biomass production by Spirulina platensis as function of nitrate and NaCl concentrations

Effects of nitrate (2.0, 2.5, and 3.0 g L^?1) and salt (0.5, 1.0, 1.5, 2.0 g L^?1) concentrations on biomass production by Spirulina platensis was examined in the Schlösser medium. The highest (p < 0.001) biomass yields and chlorophyll a content was observed at 2.5 g L^?1 nitrate and 1.5 g L^?1 NaCl as 3.495 g L^?1 and 29.92 mg L^?1, respectively. Increment rate of biomass production was especially found between 72 and 216 h. Modified Richards, Schnute, Logistic and Gompertz models was successfully predicted (r² > 0.96 and RSS ? 0.003) biomass production by S. platensis as function of nitrate and salt concentrations. Low residual sum of squares (RSS) and high regression coefficients (r²) indicated that used models were well fitted to the experiment data and it could be regarded as sufficient to describe biomass production of Spirulina sp. Biological variables i.e. production rate (μ) and lag time (λ) for S. platensis ranged 0.012–0.034 h^?1 and 2.43–5.85 h, respectively from biomass production were successfully predicted by modified Logistic model according to low RSS and F-testing value.     

Crucial factors affecting the nitrile hydratase production of Mesorhizobium sp. F28

Mesorhizobium sp. F28 contains cobalt-NHase, which effectively converts acrylonitrile into acrylamide. When urea was added to the culture medium, the NHase activity was 62.3 U ml^?1 (R2A–R2A/urea) after 22.5 h of cultivation, which was similar to that in the medium without addition (R2A–R2A, 70.0 U ml^?1). The relative activity of the purified NHase was 100%, 92%, 94%, and 92% in the medium containing, respectively, 0 mM, 2 mM, 5 mM, and 10 mM of urea. Urea had no significant effect on the purified NHase activity of Mesorhizobium sp. F28. This research did not observe the NHase production by Mesorhizobium sp. F28 when acrylonitrile was supplemented in the culture medium except that cobalt ions existed. The highest enzyme activity was 328.5 U ml^?1 as cobalt ions were added in the pre-culture and culture medium after 22.5 h of cultivation (R2A/Co-R2A/Co); compared to media without cobalt ions (R2A–R2A, 22.5 h, 70.5 U ml^?1) this is an almost five-fold enhancement. It can be concluded that culture media containing cobalt ions was beneficial for the formation of active NHase of Mesorhizobium sp. F28.     

1,4-Diamino-2-butanone, a wide-spectrum microbicide, yields reactive species by metal-catalyzed oxidation

The α-aminoketone 1,4-diamino-2-butanone (DAB), a putrescine analogue, is highly toxic to various microorganisms, including Trypanosoma cruzi. However, little is known about the molecular mechanisms underlying DAB's cytotoxic properties. We report here that DAB (pK_a 7.5 and 9.5) undergoes aerobic oxidation in phosphate buffer, pH 7.4, at 37 °C, catalyzed by Fe(II) and Cu(II) ions yielding NH₄⁺ ion, H₂O₂, and 4-amino-2-oxobutanal (oxoDAB). OxoDAB, like methylglyoxal and other α-oxoaldehydes, is expected to cause protein aggregation and nucleobase lesions. Propagation of DAB oxidation by superoxide radical was confirmed by the inhibitory effect of added SOD (50 U ml^? 1) and stimulatory effect of xanthine/xanthine oxidase, a source of superoxide radical. EPR spin trapping studies with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) revealed an adduct attributable to DMPO–HO^?, and those with α-(4-pyridyl-1-oxide)-N-tert-butylnitrone or 3,5-dibromo-4-nitrosobenzenesulfonic acid, a six-line adduct assignable to a DAB^? resonant enoyl radical adduct. Added horse spleen ferritin (HoSF) and bovine apo-transferrin underwent oxidative changes in tryptophan residues in the presence of 1.0–10 mM DAB. Iron release from HoSF was observed as well. Assays performed with fluorescein-encapsulated liposomes of cardiolipin and phosphatidylcholine (20:80) incubated with DAB resulted in extensive lipid peroxidation and consequent vesicle permeabilization. DAB (0–10 mM) administration to cultured LLC-MK2 epithelial cells caused a decline in cell viability, which was inhibited by preaddition of either catalase (4.5 μM) or aminoguanidine (25 mM). Our findings support the hypothesis that DAB toxicity to several pathogenic microorganisms previously described may involve not only reported inhibition of polyamine metabolism but also DAB pro-oxidant activity.     

Electrochemical oxidation behavior of guanine and adenine on graphene–Nafion composite film modified glassy carbon electrode and the simultaneous determination

The electrochemical behavior of guanine and adenine on the graphene and Nafion composite film modified glassy carbon electrode was investigated by differential pulse voltammetry (DPV). The results indicated that the modified electrode exhibited an excellent electrocatalytic activity towards the oxidation of guanine and adenine, testified by the increased oxidation peak current and decreased oxidation potential. The experimental conditions were optimized. The separation of the two oxidation peaks was 0.364 V in 0.1 M pH 4.4 acetate buffer solution (ABS). Based on this, a novel electrochemical method was proposed to simultaneously determine guanine and adenine with the detection limit of 0.58 (guanine) and 0.75 (adenine) μM (S/N = 3). The proposed method was applied to determine guanine and adenine in milk powder, urine and herring sperm DNA samples with satisfactory results. The value of (G + C)/(A + T) in herring sperm DNA was calculated to be 0.8065. The fabricated electrode showed excellent reproducibility, stability and anti-interference.     

Methane output of rabbits (Oryctolagus cuniculus) and guinea pigs (Cavia porcellus) fed a hay-only diet: implications for the scaling of methane production with body mass in non-ruminant mammalian herbivores

It is assumed that small herbivores produce negligible amounts of methane, but it is unclear whether this is a physiological peculiarity or simply a scaling effect. A respiratory chamber experiment was conducted with six rabbits (Oryctolagus cuniculus, 1.57 ± 0.31 kg body mass) and six guinea pigs (Cavia porcellus, 0.79 ± 0.07 kg) offered grass hay ad libitum. Daily dry matter (DM) intake and DM digestibility were 50 ± 6 g kg^? 0.75 d^? 1 and 55 ± 6% in rabbits and 59 ± 11 g kg^? 0.75 d^? 1 and 61 ± 3% in guinea pigs, respectively. Methane production was similar for both species (0.20 ± 0.10 L d^? 1 and 0.22 ± 0.08 L d^? 1) and represented 0.69 ± 0.32 and 1.03 ± 0.29% of gross energy intake in rabbits and guinea pigs, respectively. In relation to body mass (BM) guinea pigs produced significantly more methane. The data on methane per unit of BM obtained in this study and from the literature on the methane output of elephant, wallabies and hyraxes all lay close to a regression line derived from roughage-fed horses, showing an increase in methane output with BM. The regression, including all data, was nearly identical to that based on the horse data only (methane production in horses [L d^? 1] = 0.18 BM [kg]^{0.97 (95%CI 0.92–1.02)}) and indicates linear scaling. Because feed intake typically scales to BM^0.75, linear scaling of methane output translates into increasing energetic losses at increasing BM. Accordingly, the data collection indicates that an increasing proportion of ingested gross energy is lost because relative methane production increases with BM. Different from ruminants, such losses (1%–2% of gross energy) appear too small in non-ruminant herbivores to represent a physiologic constraint on body size. Nevertheless, this relationship may represent a physiological disadvantage with increasing herbivore body size.     

Application of single drop liquid-liquid-liquid microextraction for the determination of fluoroquinolones in human urine by capillary electrophoresis

A simple and novel method of single drop liquid–liquid–liquid microextraction (SD-LLLME) coupled with capillary electrophoresis (CE) for the determination of six fluoroquinolones (FQs) was developed. The method was eventually applied to extraction and preconcentration of FQs in human urine samples. Good linear relationships were obtained for all analytes in a range of 40–1000 μg L^?1 with the correlation coefficients from 0.9913 to 0.9995. The limit of detections (LODs) varied from 7.4 to 31.5 μg L^?1 at a signal-to-noise (S/N) of 3. The recoveries at two spiking levels were 81.8–104.9% with relative standard deviations <8.3%.     

Development of electrochemical sulfite biosensor based on SOX/PBNPs/PPY modified Au electrode

A sulfite oxidase (SO_X) (EC 1.8.3.1) purified from Syzygium cumini leaves was immobilized onto Prussian blue nanoparticles/polypyrrole (PBNPs/PPY) nanocomposite film electrodeposited onto the surface of gold (Au) electrode. An electrochemical sulfite biosensor was fabricated using SO_X/PBNPs/PPY/Au electrode as working electrode, Ag/AgCl as standard electrode and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier Transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) at different stages of its construction. The biosensor showed optimum response within 2 s, when operated at 20 mV s⁻¹ in 0.1 M Tris–HCl buffer, pH 8.0 and at 30 °C. Linear range and minimum detection limit were 0.5–1000 μM and 0.1 μM (S/N = 3) respectively. The sensor was evaluated with 95.0% recovery of added sulfite in red wine samples and 1.9% and 3.3% within and between batch coefficients of variation respectively. There was a good correlation (r = 0.96) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was employed for determination of sulfite level in red, white and rose wine samples. The enzyme electrode was used 300 times over a period of 4 months, when stored at 4 °C.     

Horseradish peroxidase compound I as a tool to investigate reactive protein-cysteine residues: from quantification to kinetics

Proteins containing reactive cysteine residues (protein-Cys) are receiving increased attention as mediators of hydrogen peroxide signaling. These proteins are mainly identified by mining the thiol proteomes of oxidized protein-Cys in cells and tissues. However, it is difficult to determine if oxidation occurs through a direct reaction with hydrogen peroxide or by thiol–disulfide exchange reactions. Kinetic studies with purified proteins provide invaluable information about the reactivity of protein-Cys residues with hydrogen peroxide. Previously, we showed that the characteristic UV–Vis spectrum of horseradish peroxidase compound I, produced from the oxidation of horseradish peroxidase by hydrogen peroxide, is a simple, reliable, and useful tool to determine the second-order rate constant of the reaction of reactive protein-Cys with hydrogen peroxide and peroxynitrite. Here, the method is fully described and extended to quantify reactive protein-Cys residues and micromolar concentrations of hydrogen peroxide. Members of the peroxiredoxin family were selected for the demonstration and validation of this methodology. In particular, we determined the pK_a of the peroxidatic thiol of rPrx6 (5.2) and the second-order rate constant of its reactions with hydrogen peroxide ((3.4 ± 0.2) × 10⁷ M^? 1 s^? 1) and peroxynitrite ((3.7 ± 0.4) × 10⁵ M^? 1 s^? 1) at pH 7.4 and 25 °C.     

Soybean residues sequestration affected by different tillage practices and the impacts on soil microbial characteristics and enzymatic activities

A large quantity of leaf litter was left on soil surface after soybean (Glycine max) harvest in the black soil region, northeast of China, where soybean was planted with the largest area. This paper investigated the effects of different fall tillage practices on soybean leaf litter sequestration into soil, and the subsequently durative effects on soil biological and biochemical properties during the next growing season. Two practices were investigated, fall tillage (T) and no fall tillage (NT) after soybean harvest in autumn. Results showed that the residue biomass on soil surface and in subsoil profile (0–20 cm) after soybean harvest was about 1450 kg ha^?1 and 340 kg ha^?1, respectively in October 2006. The residue biomass on soil surface and in subsoil profile was about 84 kg ha^?1, 1581 kg ha^?1 for T, and 423 kg ha^?1, 340 kg ha^?1 for NT respectively in May 2007. It was obvious that T practice can more effectively sequester leaf litter into soil compared to NT. Results also showed that T practices after soybean harvest eminently improved soil microbial carbon biomass and nitrogen biomass contents, and significantly improved soil urease and acid phosphate activities than NT. No significant difference of dehydrogenase activity was found between N and NT. The positive effects of T treatment on Soil microbial properties and soil enzymes activities among the next growing season due to soybean residues sequestration performed durative profit.     

Development of urinary albumin immunosensor based on colloidal AuNP and PVA

The development of immunosensors with high sensitivity and specificity in detecting the pathogenic or physiologically relevant molecules in the body, offers a powerful opportunity in early diagnosis and treatment of diseases. In this study, we developed a new competitive immunosensor with employing antibody (Ab) labeled AuNP (Ab-AuNP) and PVA modified screen-printed carbon electrode (SPCE) surface to detect the urine albumin. Field emission scanning electron microscopy (FE-SEM) of modified electrode showed a suitable and stable attachment between HSA antigen- mAb and AuNP. Cyclic voltammetric (CV) method demonstrated that modification process was well performed. Electrochemical measurements including differential pulse voltammetry (DPV) and square wave voltammetry (SWV) were employed for quantitative antigen detection. The electrochemical measurements performed with other proteins mixed with samples demonstrated a high specificity and selectivity for this biosensor in detecting the HSA. In optimal conditions, the immunosensor could detect HSA in a high linear range (from 2.5 to 200 μg/mL) with a low detection limit of 25 ng/mL. This new strategy could be improved and applied to detect the other antigen.