Validation of dot blot immunoassay for measurement of complement opsonization of nanoparticles

Complement plays a critical role in the immune response toward nanomaterials. The complement attack on a foreign surface results in the deposition of C3, assembly of C3 convertases, the release of anaphylatoxins C3a and C5a, and finally, the formation of membrane attack complex C5b-9. Various technologies can measure complement activation markers in the fluid phase, but measurements of surface C3 deposition are less common. Previously, we developed an ultracentrifugation-based dot blot immunoassay (DBI) to measure the deposition of C3 and other protein corona components on nanoparticles. Here, we validate the repeatability of the DBI and its correlation with pathway-specific and common fluid phase markers. Moreover, we discuss the advantages of DBI, such as cost-effectiveness and versatility, while addressing potential limitations. This study provides insights into complement activation at the nanosurface level, offering a valuable tool for nanomedicine researchers in the field.

Evaluation of the Histoplasma capsulatum 100-kilodalton antigen dot blot for the rapid diagnosis of progressive histoplasmosis in HIV/AIDS patients

Among people living with HIV (PLHIV), progressive disseminated histoplasmosis (PDH) represents an important cause of mortality. Since antigen detection allows a rapid diagnosis and the instauration of a specific treatment this study aimed to evaluate the analytical performance of the Hcp100 dot blot, an in-house assay that detects the Histoplasma capsulatum 100-kilodalton antigen in urine and compare it with 2 commercially available assays the Histoplasma Urine Antigen Lateral Flow Assay (MVD-LFA) (MiraVista® Diagnostics) and the Clarus Histoplasma Galactomannan EIA (Clarus HGM) (IMMY). Urine specimens from 23 PLHIV with PDH, 13 patients with other infectious diseases, and 20 healthy individuals were tested. The Hcp100 dot blot showed higher sensitivity (87.0%), specificity (97.0%) and accuracy (92.9%) than the MVD-LFA (73.9%, 78.8%, and 76.8%, respectively) and the Clarus HGM (78.3%, 90.9%, and 85.7%, respectively). The Hcp100 dot blot had high analytical performance and would be a valuable screening tool for diagnosing PDH among PLHIV.

Identification of G-quadruplex anti-Interleukin-2 aptamer with high specificity through SELEX stringency

Aptamers are short single-stranded oligonucleotides capable of binding to various targets with high specificity and affinity. This study aimed to identify an aptamer against mouse interleukin-2 (mIL-2) as one of the most important cytokines in autoimmune diseases for diagnostic and therapeutic purposes. For this purpose, 14 SELEX rounds were performed on recombinant mIL-2 with high stringency. The dot blot and flow cytometry techniques were conducted to determine affinity, dissociation constant (K_d), specificity, and SELEX rounds screening. The stringency of rounds was considered based on aptamer/target incubation time, washing steps, and target proteins. Finally, the aptamer's structure was mapped and predicted by M-fold and QGRS Mapper web-based software. After 14 rounds, the flow cytometry analysis revealed that the 11^th round was a proper round. The high-affinity aptamers M20 and M15 were chosen for their ability to bind mIL-2. According to DNA folding software, M20 and M15 aptamers had G-quadruplex and stem-loop structures, respectively. The M20 aptamer affinity was greater than M15, and its predicted K_d was 91 nM. A simple SELEX protocol with round stringency was explained to identify DNA aptamers against protein targets. The reported G-quadruplex aptamer might have potential diagnostic or therapeutic application in IL-2–related disorders.

Aptamers as the powerhouse of dot blot assays

Dot blot assays have always been associated with antibodies as the main molecular recognition element, which are widely employed in a myriad of diagnostic applications. With the rising of aptamers as the equivalent molecular recognition elements of antibodies, dot blot assays are also one of the diagnostic avenues that should be scrutinized for their amenability with aptamers as the potential surrogates of antibodies. In this review, the stepwise procedures of an aptamer-based dot blot assays are underscored before reviewing the existing aptamer-based dot blot assays developed so far. Most of the applications center on monitoring the progress of SELEX and as the validatory assays to assess the potency of aptamer candidates. For the purpose of diagnostics, the current effort is still languid and as such possible suggestions to galvanize the move to spur the aptamer-based dot blot assays to a point-of-care arena are discussed.

Quantification of matrix metalloproteinases MMP-8 and MMP-9 in gingival overgrowth

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Protein dot-blot method is suitable to compare expression levels of MMP-8 and MMP-9 in gums.

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The relative levels of MMP-8 and MMP-9 in mild and moderate gingival overgrowth were measured.

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Biological variability among individuals did not affect assay development.

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The protein dot blot was fast, highly sensitive, repeatable and economic.

Background

Matrix metalloproteinases (MMPs) are proteolytic enzymes involved in extracellular matrix remodeling of all body tissues, including oral tissues such as gingival tissue. Expression levels of MMPs are widely studied as important biomarkers for explaining the biochemical mechanisms and evolution of many oral diseases.

Objective

Demonstrate the sensitivity, reproducibility, repeatability, and robustness of the dot blot assay for the relative quantification of MMP-8 and MMP-9 expression levels in patients with GO associated with orthodontic treatment.

Methods

A validated dot blot assay was used to compare the relative expression levels of MMP-8 and MMP-9 in gingival samples. Methodological variability, reproducibility, sensitivity and robustness were determined with the use of control samples from healthy donors (G1). Next, expression levels were measured in gingival tissue from patients with mild and moderate gingival overgrowth associated with orthodontic treatment (G3 and G4) and patients without gingival overgrowth but with a history of using orthodontic appliances (G2).

Results

Dot blot assay demonstrated that MMP-8 and MMP-9 expression levels were higher in patients with gingival overgrowth and distinguished those with moderate clinical grade (G4) from those with mild overgrowth (G3). In addition, patients with a history of orthodontic treatment showed similar expression levels to the control group two years after removing orthodontic appliances.

Conclusions

With the assay used, we were able to detect differences in MMP-8 and MMP-9 expression in patients with different levels of severity of gingival overgrowth. Dot blot could be used to measure MMPs during the onset and progression of gingival overgrowth.

Development of a quick dot blot assay for the titering of bovine ephemeral fever virus

Background

Bovine ephemeral fever virus (BEFV) causes fever and muscle stiffness in cattle, resulting in negative economic impact for cattle and dairy farms. During the manufacturing process of inactivated vaccine for virus control, it is important to determine the virus titer, but traditional methods such as plaque assay and TCID₅₀ assay require days of waiting time. We sought to develop a quick dot blot assay for BEFV titering.

Results

Three different kinds of BEFV antigens were prepared to raise primary antibodies for BEFV detection in dot blot assays: 1) purified BEFV particles, 2) Escherichia coli (E. coli)-expressed BEFV G1 region, and 3) E. coli-expressed BEFV N protein. Results showed that antibodies raised against purified BEFV particles can detect BEFV particles, but it also showed a high background level from the proteins of BHK-21 cells. Antibodies raised against E.coli-expressed BEFV G1 region could not detect BEFV particles in dot blot assays. Finally, antibodies raised against E.coli-expressed BEFV N protein detected BEFV particles with a high signal-to-noise ratio in dot blot assays.

Conclusions

E.coli-expressed N protein is a suitable antigen for the production of antiserum that can detect BEFV particles with a high signal-to-noise ratio. A dot blot assay kit using this antiserum can be developed as a quick and economical way for BEFV titering.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-2059-6) contains supplementary material, which is available to authorized users.

Selection of DNA aptamers against Human Cardiac Troponin I for colorimetric sensor based dot blot application

Troponin T and I are ideal markers which are highly sensitive and specific for myocardial injury and have shown better efficacy than earlier markers. Since aptamers are ssDNA or RNA that bind to a wide variety of target molecules, the purpose of this research was to select an aptamer from a 79bp single-stranded DNA (ssDNA) random library that was used to bind the Human Cardiac Troponin I from a synthetic nucleic acids library by systematic evolution of ligands exponential enrichment (Selex) based on several selection and amplification steps. Human Cardiac Troponin I protein was coated onto the surface of streptavidin magnetic beads to extract specific aptamer from a large and diverse random ssDNA initial oligonucleotide library. As a result, several aptamers were selected and further examined for binding affinity and specificity. Finally TnIApt 23 showed beast affinity in nanomolar range (2.69nM) toward the target protein. A simple and rapid colorimetric detection assay for Human Cardiac Troponin I using the novel and specific aptamer-AuNPs conjugates based on dot blot assay was developed. The detection limit for this protein using aptamer-AuNPs-based assay was found to be 5ng/ml.

Assay of antioxidant potential of two Aspergillus isolates by different methods under various physio-chemical conditions

The objective of this work was to screen fungi isolated from soil of different areas of Punjab, India for antioxidant activity by dot blot assay and around 45% of fungal isolates demonstrated antioxidant potential. Two selected strains of Aspergillus spp (Aspergillus PR78 and Aspergillus PR66) showing quantitatively best antioxidant activity by DPPH assay were further tested for their reducing power, ferrous ion and nitric oxide ion scavenging activity, FRAP assay and total phenolic content. Different physio-chemical parameters were optimized for enhancement of the activity. This revealed stationary culture grown for 10 days at 25 (o)C at pH 7 to be the best for antioxidant activity. Sucrose in the medium as carbon source resulted in highest antioxidant activity. Sodium nitrate, yeast extract, and peptone were good sources of nitrogen but sodium nitrate was the best among these. The extraction of the broth culture filtrates with different solvents revealed ethyl acetate extract to possess the best antioxidant activity. The activity as expressed by ethyl acetate extract of Aspergillus PR78 was equally effective as that of commonly used antioxidant standard, ascorbic acid.