Blocking-Free ELISA Using a Gold Nanoparticle Layer Coated Commercial Microwell Plate

Bovine Serum Albumin Conjugation in Superparamagnetic/Poly(methyl methacrylate) Nanoparticles as an Alternative for Magnetic Enzyme-Linked Immunosorbent Assays

Nanomaterials, such as magnetic nanoparticles have attracted significant attention of medical area due to their capacity to improve the performance of immunoassays. Therefore the aim of this work was to study the bovine serum albumin (BSA) conjugation in superparamagnetic (MNPs)/poly(methyl methacrylate) (PMMA) nanoparticles with further characterization and application in enzyme-linked immunosorbent (ELISA) assay. The successful conjugation of BSA in MNPs- PMMA nanoparticles was confirmed by several techniques, including light scattering, zeta potential, transmission electron microscopy (TEM) and Lowry protein quantification assay. The superparamagnetic properties were confirmed by vibrating sample magnetometer. BSA conjugated MNPs-PMMA nanoparticles presented higher interactions with antibody than free BSA. The BSA + MNPs-PMMA nanoparticles (magnetic ELISA assay) reduced the time and increased the sensibility of traditional ELISA assay, reinforcing the idea that the use these nanomaterials are an excellent alternative for the immunoassays field.

Kaempferol inhibits the cell migration of human hepatocellular carcinoma cells by suppressing MMP-9 and Akt signaling

Metastasis is the most prevalent cause of cancer-related deaths and treatment failure in patients with hepatocellular carcinoma (HCC). Kaempferol is a natural flavonol belonging to the subgroup of flavonoids and exhibits potent anticancer activities. This study provides molecular evidence on the anti-invasive and anti-migratory effects of kaempferol on human HCC cells. The anti-invasive effect was investigated by applying kaempferol on two human HCC cell lines (Huh-7 and SK-Hep-1). Kaempferol reduced the invasion and migration of Huh-7 and SK-Hep-1 cells by Boyden chamber invasion assay and wound healing assay, respectively. A protease array analysis showed that Matrix Metalloproteinase-9 (MMP-9) was dramatically downregulated in HCC cells after kaempferol treatment. Gelatin zymography and Western blot assay showed that kaempferol reduced the activities and protein expression of MMP-9, respectively. Kaempferol also sufficiently suppressed the phosphorylation of the Akt expression. Overall, kaempferol inhibited the invasive properties of human HCC cells by targeting MMP-9 and Akt pathways. Hence, kaempferol could be used as an adjuvant therapeutic agent for the treatment of human HCC cells.

Comprehensive characterization of gold nanoparticles and their protein conjugates used as a label by hollow fiber flow field flow fractionation with photodiode array and fluorescence detectors and multiangle light scattering

Most of lateral flow immunoassay (LFIA) devices rely on gold nanoparticles (GNP) labeled antibodies or other biospecific proteins, to achieve reagent-less color-based detection. GNP size, GNP-protein conjugation level and its stability are crucial points for the development of precise and accurate methods. In addition, the purification of the GNP-protein conjugates from unreacted protein and GNP, is necessary for adequate analytical performance of the assay. To assist the synthesis and production process of GNP and their protein conjugates, we use for the first time a non-destructive, particle separation-multi-detection approach based on miniaturized flow field flow fractionation (HF5). A separation method was developed to baseline size-separate GNP, GNP-protein, protein and GNP including BSA used as a surface coater in less than 30 minutes. Freshly synthesized GNP were first characterized and then conjugated with two different model antibodies: a mouse immunoglobulin (IgG) and a fluorescein-labeled mouse immunoglobulin (FITC-IgG). The IgG-GNP complexes were fractionated using the HF5 apparatus, able to separate IgG-GNP from free proteins by their hydrodynamic size, allowing purification of the conjugation product. Both IgG-GNPs and GNPs were characterized according to their size by the MALS detector, and according to their Surface Plasmon Resonance and spectrum by UV-Vis detection, improving the results obtained via batch characterization. This simple non-invasive approach is very useful for the LFIA development and optimization: the use of HF5-mutidetection offers a unique tool for this purpose facilitating the industrialization of the process and the relate optimization and standardization.

Alginate Hydrogel-Embedded Capillary Sensor for Quantitative Immunoassay with Naked Eye

We have developed an alginate hydrogel-embedded capillary sensor (AHCS) for naked eye-based quantification of immunoassay. Alkaline phosphatase (ALP) can modulate gel-sol transformation to increase the permeability of Cu²⁺-cross-linked alginate hydrogel film in the AHCS, followed by solution exchange into the capillary. Through measuring the length of the liquid phase of the microfluidics in the capillary at a given time, the concentration of the ALP could be quantified with the naked eye. Since ALP is widely applied as a signal reporter for immunoassays, the AHCS could easily accommodate conventional immune sensing platforms. We justify the practicality of AHCS with hepatitis B virus surface antigen (HBsAg) in serum samples and got comparable results with commercialized immunoassay. This AHCS is easy to make and use, effective in cost, and robust in quantification with the naked eye, showing great promise for next generation point-of-care testing.

Highly Sensitive Detection of PCV2 Based on Tyramide Signals and GNPL Amplification

The frequent emergence of secondary infection and immunosuppression after porcine circovirus type 2 (PCV2) infection highlights the need to develop sensitive detection methods. A dual-signal amplification enzyme-linked immunosorbent assay (ELISA) based on a microplate coated with gold nanoparticle layers (GNPL) and tyramide signal amplification (TSA) was established. Results confirmed that the microplates coated with GNPL have a strong binding ability to the antibody without affecting the biological activity of the antibody. The microplates coated with GNPL have strong binding ability to the antibody, and the amplification of the tyramide signal is combined to further improve the sensitivity of PCV2. The PCV2 antibody does not crossreact with other viruses, demonstrating that the method has good specificity. A dual-signal amplification strategy is developed using microplates modified with GNPL and TSA to sensitively detect PCV2.