Ultrasensitive fluorescence detection of antitumor drug methotrexate based on a terbium-doped silica dendritic probe.

A novel strategy was developed for the detection of methotrexate (MTX) via the quenching effect of MTX on the fluorescence intensity of terbium-doped dendritic silica particles (Tb@KCC-1). The fluorescence intensity of Tb@KCC-1 can be effectively quenched by MTX at 546 nm under an excitation wavelength of 233 nm. The quenched fluorescence is proportional to the amount of MTX in both plasma and exhaled breath condensate (EBC) samples. Under the optimal conditions, the linear dynamic ranges of the developed method were 44 nM to 2.2 µM for EBC, 44 nM to 0.22 µM and 0.22-2.2 µM for plasma samples. The limit of detection (LOD) and limit of quantification (LOQ) in both plasma and EBC media are 35 and 116 nM, respectively. The developed method has the benefits of fast analysis time, simple approach, high specificity, and sensitivity for the detection of MTX in both media. This nanoprobe has been successfully utilized for the quantification of MTX in patients' plasma and spiked EBC samples, proving the applicability of the nanoprobe for MTX detection in real samples.

Visual monitoring and optical recognition of digoxin by functionalized AuNPs and triangular AgNPs as efficient optical nano-probes.

In this study, we presented elective, sensitive, and rapid UV-Vis spectrophotometry and calorimetric assay for the recognition of digoxin. Therefore, cysteamine-gold nanoparticles (Cys A-AuNPs) in the presence of cysteine acid amine and Silver nanoparticles in the presence of tetramethyl benzidine and hydrogen peroxide (AgNPs-TMB [3,3',5,5'-tetramethylbenzidine]-H2 O2 ) were synthesized and utilized as the desired probe. Finally, color variation of probes was observed in the absence and presence of digoxin. Obtained results indicate that the color of Cys A-AuNPs changed from dark pink to light in the absence and the presence of digoxin, respectively. Also, the color of AgNPs-TMB-H2 O2 changed from dark blue to light blue, in the absence and the presence of digoxin, respectively. Moreover, UV-Vis spectroscopies results indicate digoxin with a low limit of quantification of 0.125 ppm in human plasma samples which linear range was 0.125 to 11 ppm.

Chemical binding of molecular-imprinted polymer to biotinilated antibody: Utilization of molecular imprinting polymer as intelligent synthetic biomaterials toward recognition of carcinoma embryonic antigen in human plasma sample.

In this study, a novel biosensor based on molecular imprinting polymer (MIP) methodology was fabricated toward recognition of carcinoembryonic antigen (CEA). For this purpose, poly (toluidine blue) (PTB) was electropolymerized on the surface of gold electrode in the absence and presence of CEA. So, the target molecules were entrapped into the imprinted specific cavities of MIP. Obtained results show that, the binding affinity of the MIP system was significantly higher than that of revealed for the nonimprinted polymer (NIP) system, MIP-based biosensor revealed linear response from (0.005 to 75 µg/L) and low limit of quantification of (0.005 µg/L) by using chronoamperometry technique, leading to CEA monitoring in real and clinical samples. Thus, a novel technique for rapid, simple, sensitive and affordable monitoring of CEA (LLOQ = 0.005 µg/L) has provided through developed biosensor. From a future perspective, moreover, this method can be considered as an applicable candidate in biomedical and clinical analysis for point-of-care usages.

Development of a reliable bioanalytical method based on prostate specific antigen trapping on the cavity of molecular imprinted polymer towards sensing of PSA using binding affinity of PSA-MIP receptor: A novel biosensor.

In this study, electrically-conducting poly [Toluidine Blue (PTB)] was applied as artificial receptor. It was organized by molecular imprinting approaches and via electrochemical technique for the sensitive monitoring of prostate-specific antigen (PSA). The protein-imprinted PTB was electropolymerized in a pre-formed glutaraldehyde-cysteamine (GA-Cys A) matrix on the surface of gold electrode, which significantly boosted the stability against degradation of the Molecular Imprinted Polymer (MIP) on the surface of pre-modified gold electrode. Moreover, the MIP bio-receptor ability towards protein recognition was explored by some electrochemical techniques. The binding affinity of MIP system was considerably upper than that of non-imprinted polymer (NIP) system, indicating the success of the method in generating imprinted materials that was specifically use to PSA protein. The incubation of the MIP modified electrode in various concentration of PSA (from 1-60 µg/L) resulted in the increase of the Fe (CN)63-/4- redox peak current. The bio-device also showed linear response from 1-60 µg/L and LLOQ of 1 µg/L by using DPV technique, leading to PSA monitoring in clinical samples. The proposed MIP-based biosensor was satisfactorily applied to the determination of PSA in human plasma samples. Therefore, the developed bio-device provides a new approach for sensitive, simple, rapid, and cost-effective monitoring of 1 µg/L of PSA. Notably, this approach could appear as an appropriate candidate for point-of-care (POC) use in clinical and biomedical analyses.

Biosensing of prostate specific antigen (PSA) in human plasma samples using biomacromolecule encapsulation into KCC-1-npr-NH2: A new platform for prostate cancer detection.

Prostate-specific antigen (PSA) is a high molecular weight glycoprotein that is used as a marker for the diagnosis of prostate cancer and is therefore important in the medical field. In this study, a novel sandwich type immunoassay was designed based on encapsulation of biotinylated antibody into KCC-1-npr-NH2. KCC-1-npr-NH2 stabilized the stability of the primary antibody. So, encapsulated Ab1 was immobilized on the surface of glassy carbon electrode. Field emission scanning electron microscope (FE-SEM) was employed to monitor the sensor fabrication. The engineered immunosensor was used for the detection of PSA using differential pulse voltammetry (DPVs) and square wave voltammetry (SWVs) techniques. The proposed interface lead to enhancement of accessible surface area for immobilizing a high amount of anti-PSA antibody, increasing electrical conductivity, boosting stability, catalytic properties and biocompatibility. The intensity of electrochemical signals is also increased by the use of AuNPs functionalized with CysA used in secondary antibody (HRP conjugated PSA) structure. Under optimal conditions, the designed immuno-assay provide a good analytical performance for quantifying the PSA marker in the linear range of 1 to 60 µg/l.

Ultrasensitive immunoassay of glycoprotein 125 (CA 125) in untreated human plasma samples using poly (CTAB­chitosan) doped with silver nanoparticles.

CA 125 is a Mucin glycoprotein and its concentration in human serum correlates with a woman's risk of developing ovarian cancer and also indicates response to therapy in diagnosed patients. Accurate detection of this large, complex protein in patient biofluids is of great clinical relevance. In this work, an innovative immunoassay for quantitation of CA 125 based on signal amplification strategy was proposed. In this work, Horseradish peroxidase (HRP) labeled CA 125-antibody (anti-CA 125) was immobilized onto a green and biocompatible nanocomposite containing poly cetyl trimethyl ammonium bromide (P (CTAB) as conductive matrix, chitosan (CS) as biocompatible agent and sliver nanoparticles (Ag NPs) as signal amplification element. Therefore, a novel nanocomposite film based P (CTAB-CS) and Ag NPs was exploited to develop a highly sensitive immunosensor for detection of CA 125 protein. Importantly, Ag NPs prepared by electrodeposition method which lead to compact morphology. Fully electrochemical methodology was used to prepare a new transducer on a glassy carbon surface which provided a high surface area to immobilize a high amount of the anti-CA 125. The surface morphology of electrode was characterized by high-resolution field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDS). The immunosensor was employed for the detection of CA 125 using cyclic voltammetry (CV) and differential pulse voltammetry (DPVs) techniques. Under optimized condition the calibration curve for CA 125 concentration by SWV and DPV was linear in 0.01-400 U/mL with lower limit of quantification of 0.001 U/mL. The method was successfully applied assay of the CA 125 in unprocessed human plasma samples.