Micro-bead injection spectroscopy for label-free automated determination of immunoglobulin G in human serum

Automated renewable label-free optical sensor for quantification of therapeutic monoclonal antibodies

Biopharmaceuticals, particularly monoclonal antibodies (mAbs), are essential for treating cancer, autoimmune disorders, and infectious diseases. These complex biologics require precise manufacturing and regulatory strategies. Process analytical technology enables the analysis and control of biopharmaceuticals' manufacturing processes through timely measurements of critical quality and performance attributes, aiming to ensure product quality. The production of high-quality therapeutic mAbs becomes challenging due to the high cost of analytical methods. In this work, a miniaturized approach based on UV-Vis micro-bead injection spectroscopy within a lab-on-valve platform is proposed for the quantitative, label-free determination of therapeutic mAbs, specifically rituximab (RTX), in cell culture supernatants. The sensor is automatically assembled, through computer-controlled, fluidic manipulation of Concanavalin A-Sepharose beads. These beads enable recognition of glycosylated mAbs, facilitating on-column label free optical density measurement at 280 nm. Beads are discarded after each determination, avoiding carrying-over between samples. Key parameters were optimized to enhance sensitivity and repeatability of RTX detection. The method demonstrated good linearity (0.25-1.50 mg mL-1, R > 0.9970), with a limit of detection of 0.11 mg mL-1. Each determination required 8 min of total analysis and 0.12 mg of sorbent. When applied to surrogate cell culture supernatants, the μ-BIS-LOV sensor exhibited consistent recovery rates across different dilutions, confirming its suitability for bioprocess monitoring and quality control of biopharmaceuticals. This method offers a simplified, cost-effective alternative to traditional analytical techniques, reducing reagent consumption and eliminating the need for secondary antibodies, offering an efficient solution for quality control in biopharmaceutical production.

MOF scaffold for anchoring platinum-nickel nanoparticles with enhanced oxidase-like activity to improve lateral flow immunoassay diagnosis

Noble metal nanoparticles have attracted tremendous attention as the promising signal reporters for catalytic-colorimetric lateral flow immunoassay (LFIA). However, it remains great challenges for improving their stability and catalytic activity. Herein, first, a kind of porphyrinic based metal-organic framework (MOF) was used as a carrier for loading platinum (Pt) nanoparticles to avoid its aggregation. Moreover, nickel (Ni) atoms were dopped into Pt nanoparticles to adjust crystal structure, thus greatly improving catalytic activity. The resulting MOF@PtNi nanocomposite showed enhanced colorimetric signal brightness and excellent oxidase-like activity, which can improve sensitivity via amplifying the color signal. The catalytic mechanism was further studied by scavenger and electron paramagnetic resonance analysis. Furthermore, integrated with the competitive immunization LFIA platform, the high sensitivity colorimetric detection of human immunoglobulin G was realized with a detection limit of 0.378 ng/mL and 0.269 ng/mL for pre- and post-catalytic detection, respectively. In addition, this MOF@PtNi based catalytic-colorimetric LFIA was used for detection of clinical serum samples and the results agreed well with that measured by the standard method. Therefore, this study helps open up the application of proposed catalytic-colorimetric nanocomposite in the ultrasensitive LFIA for point-of-care diseases diagnosis.

Lab-on-Valve Automated and Miniaturized Assessment of Nanoparticle Concentration Based on Light-Scattering

Nanoparticles (NPs) concentration directly impacts the dose delivered to target tissues by nanocarriers. The evaluation of this parameter is required during NPs developmental and quality control stages, for setting dose-response correlations and for evaluating the reproducibility of the manufacturing process. Still, faster and simpler procedures, dismissing skilled operators and post-analysis conversions are needed to quantify NPs for research and quality control operations, and to support result validation. Herein, a miniaturized automated ensemble method to measure NPs concentration was established under the lab-on-valve (LOV) mesofluidic platform. Automatic NPs sampling and delivery to the LOV detection unit were set by flow programming. NPs concentration measurements were based on the decrease in the light transmitted to the detector due to the light scattered by NPs when passing through the optical path. Each analysis was accomplished in 2 min, rendering a determination throughput of 30 h^-1 (6 samples h^-1 for n = 5) and only requiring 30 μL (≈0.03 g) of NPs suspension. Measurements were performed on polymeric NPs, as these represent one of the major classes of NPs under development for drug-delivery aims. Determinations for polystyrene NPs (of 100, 200, and 500 nm) and for NPs made of PEGylated poly-d,l-lactide-co-glycolide (PEG-PLGA, a biocompatible FDA-approved polymer) were accomplished within 10⁸-10¹² particles mL^-1 range, depending on the NPs size and composition. NPs size and concentration were maintained during analysis, as verified for NPs eluted from the LOV by particle tracking analysis (PTA). Moreover, concentration measurements for PEG-PLGA NPs loaded with an anti-inflammatory drug, methotrexate (MTX), after their incubation in simulated gastric and intestinal fluids were successfully achieved (recovery values of 102-115%, as confirmed by PTA), showing the suitability of the proposed method to support the development of polymeric NPs targeting intestinal delivery.

AuNP array coated substrate for sensitive and homogeneous SERS-immunoassay detection of human immunoglobulin G

Owing to the high sensitivity, fast responsiveness and high specificity, immunoassays using surface-enhanced Raman scattering (SERS) as the readout signal displayed great potential in disease diagnosis. In this study, we developed a SERS-immunoassay method for the detection of human immunoglobulin G (HIgG). Upon involving well-ordered AuA on a SERSIA substrate, the LSPR effect was further enhanced to generate a strong and uniform Raman signal through the formation of sandwich structure with the addition of target HIgG and SERSIA tag. Optimization of the assay provided a wide linear range (0.1–200 μg mL⁻¹) and low limit of detection (0.1 μg mL⁻¹). In addition, the SERS-immunoassay method displayed excellent specificity and was homogeneous, which guaranteed the practical use of this method in the quantitative detection of HIgG. To validate this assay, human serum was analysed, which demonstrated the potential advantages of SERS-immunoassay technology in clinical diagnostics.

An AuNP array coated substrate was developed for the SERS-immunoassay detection of human immunoglobulin G.

Miniaturized analytical methods for determination of environmental contaminants of emerging concern - A review

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed.

Antibody conjugation to carboxyl-modified microspheres through N-hydroxysuccinimide chemistry for automated immunoassay applications: A general procedure

Immunochemical techniques are the workhorse for sample enrichment and detection of a large variety of analytes. In contrast to classical microtiter plate-based assays, microparticles are a next generation solid support, as they promote automation of immunoassays using flow-based techniques. Antibody immobilization is a crucial step, as these reagents are expensive, and inefficient coupling can result in low sensitivities. This paper proposes a general procedure for efficient immobilization of antibodies onto TentaGel particles, via N-hydroxysuccinimide chemistry. The goal was the preparation of solid supports with optimum immunorecognition, while increasing the sustainability of the process. The influence of buffer composition, activation and coupling time, as well as the amount of antibody on the immobilization efficiency was investigated, resorting to fluorophore-labeled proteins and fluorescence imaging. Buffer pH and activation time are the most important parameters for efficient coupling. It is demonstrated, that the hydrolysis of N-hydroxysuccinimide esters occurs at similar rates as in solution, limiting the utilizable time for coupling. Finally, applicability of the generated material for automated affinity extraction is demonstrated on the mesofluidic platform lab-on-valve.