Laser-patterned paper-based flow-through filters and lateral flow immunoassays to enable the detection of C-reactive protein

Fluorescence-Quenching Lateral Flow Immunoassay for "Turn-On" and Sensitive Detection of Anti-SARS-Cov-2 Neutralizing Antibodies in Human Serum

The titer of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies (NAbs) in the human body is an essential reference for evaluating the acquired protective immunity and resistance to SARS-CoV-2 infection. In this study, a fluorescence-quenching lateral flow immunoassay (FQ-LFIA) is established for quantitative detection of anti-SARS-CoV-2 NAbs in the sera of individuals who are vaccinated or infected within 10 min. The ultrabright aggregation-induced emission properties encapsulated in nanoparticles, AIE490 NP, are applied in the established FQ-LFIA with gold nanoparticles to achieve a fluorescence "turn-on" competitive immunoassay. Under optimized conditions, the FQ-LFIA quantitatively detected 103 positive and 50 negative human serum samples with a limit of detection (LoD) of 1.29 IU mL-1 . A strong correlation is present with the conventional pseudovirus-based virus neutralization test (R2  = 0.9796, P < 0.0001). In contrast, the traditional LFIA with a "turn-off" mode can only achieve a LoD of 11.06 IU mL-1 . The FQ-LFIA showed excellent sensitivity to anti-SARS-CoV-2 NAbs. The intra- and inter-assay precisions of the established method are below 15%. The established FQ-LFIA has promising potential as a rapid and quantitative method for detecting anti-SARS-CoV-2 NAbs. FQ-LFIA can also be used to detect various biomarkers.

Microfluidic Paper-Based Device for Medicinal Diagnosis

BACKGROUND

The demand for point-of-care testing (POCT) devices has rapidly grown since they offer immediate test results with ease of use, makingthem suitable for home self-testing patients and caretakers. However, the POCT development has faced the challenges of increased cost and limited resources. Therefore, the paper substrate as a low-cost material has been employed to develop a cost-effective POCT device, known as "Microfluidic paper-based analytical devices (μPADs)". This device is gaining attention as a promising tool for medicinal diagnostic applications owing to its unique features of simple fabrication, low cost, enabling manipulation flow (capillarydriven flow), the ability to store reagents, and accommodating multistep assay requirements.

OBJECTIVE

This review comprehensively examines the fabrication methods and device designs (2D/3D configuration) and their advantages and disadvantages, focusing on updated μPADs applications for motif identification.

METHODS

The evolution of paper-based devices, starting from the traditional devices of dipstick and lateral flow assay (LFA) with μPADs, has been described. Patterned structure fabrication of each technique has been compared among the equipment used, benefits, and drawbacks. Microfluidic device designs, including 2D and 3D configurations, have been introduced as well as their modifications. Various designs of μPADs have been integrated with many powerful detection methods such as colorimetry, electrochemistry, fluorescence, chemiluminescence, electrochemiluminescence, and SER-based sensors for medicinal diagnosis applications.

CONCLUSION

The μPADs potential to deal with commercialization in terms of the state-of-the-art of μPADs in medicinal diagnosis has been discussed. A great prototype, which is currently in a reallife application breakthrough, has been updated.

Paper-Based Molecular-Imprinting Technology and Its Application

Paper-based analytical devices (PADs) are highly effective tools due to their low cost, portability, low reagent accumulation, and ease of use. Molecularly imprinted polymers (MIP) are also extensively used as biomimetic receptors and specific adsorption materials for capturing target analytes in various complex matrices due to their excellent recognition ability and structural stability. The integration of MIP and PADs (MIP-PADs) realizes the rapid, convenient, and low-cost application of molecular-imprinting analysis technology. This review introduces the characteristics of MIP-PAD technology and discusses its application in the fields of on-site environmental analysis, food-safety monitoring, point-of-care detection, biomarker detection, and exposure assessment. The problems and future development of MIP-PAD technology in practical application are also prospected.

Diagnoses Based on C-Reactive Protein Point-of-Care Tests

C-reactive protein (CRP) is an important part of the immune system's reaction to various pathological impulses such as bacterial infections, systemic inflammation, and internal organ failures. An increased CRP level serves to diagnose the mentioned pathological states. Both standard laboratory methods and simple point-of-care devices such as lateral flow tests and immunoturbidimetric assays serve for the instrumental diagnoses based on CRP. The current method for CRP has many flaws and limitations in its use. Biosensor and bioassay analytical devices are presently researched by many teams to provide more sensitive and better-suited tools for point-of-care tests of CRP in biological samples when compared to the standard methods. This review article is focused on mapping the diagnostical relevance of CRP, the applicability of the current analytical methods, and the recent innovations in the measurement of CRP level.

Development of cellulosic material-based microchannel device capable of fluorescence immunoassay of microsamples

Microfluidic immunoassay devices are a promising technology that can quickly detect biomarkers with high sensitivity. Recently, many studies implementing this technology on paper substrates have been proposed for improving cost and user-friendliness. However, these studies have identified problems with the large volume of sample required, low sensitivity, and a lack of quantitative accuracy and precision. In this paper, we report a novel structure implemented as a cellulosic material-based microchannel device capable of quantitative immunoassay using small sample volumes. We fabricated microfluidic channels between a transparent cellophane film and water-resistant paper to facilitate loading of small-volume samples and reagents, with a 40-μm-wide immunoreaction matrix constructed in the center of the microchannel using highly precise photolithography. A fluorescence sandwich immunoassay for C-reactive protein (CRP) was successfully implemented that required only a 1-μL sample volume and a 20-min reaction time. We confirmed that the limit of detection of the device was 10-20 ng/mL with a coefficient of variation under 5.6%, which is a performance level comparable to conventional plastic-based human CRP enzyme-linked immunosorbent assay (ELISA) kits. We expect that such devices will lead to the elimination of large amounts of medical waste from the use of ubiquitous diagnostics, a result that is consistent with environmental sustainability goals.