Surface plasmon enhanced light scattering biosensing: Size dependence on the gold nanoparticle tag

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. Surface plasmon enhanced light scattering (SP-LS) is a powerful new sensing SPR modality that yields excellent sensitivity in sandwich immunoassay using spherical gold nanoparticle (AuNP) tags. Towards further improving the performance of SP-LS, we systematically investigated the AuNP size effect. Simulation results indicated an AuNP size-dependent scattered power, and predicted the optimized AuNPs sizes (i.e., 100 and 130 nm) that afford extremely high signal enhancement in SP-LS. The maximum scattered power from a 130 nm AuNP is about 1700-fold higher than that obtained from a 17 nm AuNP. Experimentally, a bio-conjugation protocol was developed by coating the AuNPs with mixture of low and high molecular weight PEG molecules. Optimal IgG antibody bioconjugation conditions were identified using physicochemical characterization and a model dot-blot assay. Aggregation prevented the use of the larger AuNPs in SP-LS experiments. As predicted by simulation, AuNPs with diameters of 50 and 64 nm yielded significantly higher SP-LS signal enhancement in comparison to the smaller particles. Finally, we demonstrated the feasibility of a two-step SP-LS protocol based on a gold enhancement step, aimed at enlarging 36 nm AuNPs tags. This study provides a blue-print for the further development of SP-LS biosensing and its translation in the bioanalytical field

On-Site Detection of Carcinoembryonic Antigen in Human Serum

Real-time connectivity and employment of sustainable materials empowers point-of-care diagnostics with the capability to send clinically relevant data to health care providers even in low-resource settings. In this study, we developed an advantageous kit for the on-site detection of carcinoembryonic antigen (CEA) in human serum. CEA sensing was performed using cellulose-based lateral flow strips, and colorimetric signals were read, processed, and measured using a smartphone-based system. The corresponding immunoreaction was reported by polydopamine-modified gold nanoparticles in order to boost the signal intensity and improve the surface blocking and signal-to-noise relationship, thereby enhancing detection sensitivity when compared with bare gold nanoparticles (up to 20-fold in terms of visual limit of detection). Such lateral flow strips showed a linear range from 0.05 to 50 ng/mL, with a visual limit of detection of 0.05 ng/mL and an assay time of 15 min. Twenty-six clinical samples were also tested using the proposed kit and compared with the gold standard of immunoassays (enzyme linked immunosorbent assay), demonstrating an excellent correlation (R = 0.99). This approach can potentially be utilized for the monitoring of cancer treatment, particularly at locations far from centralized laboratory facilities.</jats:p

Cannabis sativa L. oil extract affects neuroinflammation, clinical score, and cannabinoid receptor-1 gene expression in C57bl/6 experimental autoimmune encephalomyelitis

Introduction: Multiple sclerosis (MS) is a degenerative central nervous system disease derived by immune mechanisms, which ultimately results in clinical debilities. Numerous nutraceuticals have been cited to be effective in treatment of central nervous system complications. Objectives: This study investigated the effect of Cannabis sativa L. seed oil on experimental autoimmune encephalomyelitis (EAE). Materials and Methods: Female C57bl/6 mice were assigned randomly into three groups (8 in each). Group-A received no myelin oligodendrocyte glycoprotein (MOG), group B was immunized by MOG and treated with oil, while in group C animals were immunized and treated with normal saline. Clinical scores were recorded every other day throughout the study and after four weeks, all mice were sacrificed and spinal cords were incised for molecular and histopathological evaluations. Results: Significant differences were observed in mean clinical scores between control and experiment groups (P&lt;0.001). Cannabinoid receptor-1 gene expression increased significantly in treatment group (P&lt;0.001). Histopathologic evaluations also showed a significant decrease in overall infiltrated and vacuolated area and immune cells infiltration into the central nervous system in the treatment group (P&lt;0.01). Conclusion: Cannabis sativa L. oil extract administration alleviated inflammation and paralysis in animal model. Therefore, its oil extract might be useful in soothing inflammatory and auto-immune diseases. However, additional research might be required.</jats:p

(Nano)tag–antibody conjugates in rapid tests

Antibodies are naturally derived materials with favorable affinity, selectivity, and fast binding kinetics to the respective antigens, which enables their application as promising recognition elements in the development of various types of rapid tests.</p

PCR-free paper-based nanobiosensing platform for visual detection of telomerase activity via gold enhancement

© 2020 Elsevier B.V. Telomerase activity has been demonstrated in a wide variety of most solid tumors and considered as a well-known cancer biomarker. The commonly utilized method for its detection is polymerase chain reaction (PCR)-based telomeric repeat amplification protocol (TRAP). However, the TRAP technique suffers from false-negative results caused by the failure of PCR step. Moreover, it requires advanced equipment with a tedious and time-consuming procedure. Herein, we presented a portable nitrocellulose paper-based nanobiosensing platform for ultrafast and equipment-free detection of telomerase activity based on a simple colorimetric assay that enabled naked-eye visualization of the color change in response to enzyme activity. In this platform, hybridization was initially performed between telomere complementary oligonucleotide immobilized on gold nanoparticles (GNPs) and telomerase elongated biotinylated probe. Thereafter, the assembly was attached on activated paper strip via avidin-biotin interaction. The signal amplification was carried out by enlargement of the attached GNPs on the paper strip, forming tightly compact rod-shaped submicron structures of gold representing a visual color formation. Thanks to significant sensitivity enhancement, the color change was occurred for down to 6 cells, which can be easily observed by the naked eye. Due to the desired aspects of the developed assay including PCR-free, low cost, simple, and high sensitivity, it can be used for evaluation of telomerase activity in cell extracts for future clinical applications. Furthermore, this design has the ability to be easily integrated into lab-on-chip devices for point-of-care telomerase sensing