Corrigendum to "Point-of-care testing for lysine concentration in swine serum via blue-emissive carbon dots entrapped microfluidic chip" [Animal Nutrition 12 (2023) 236-244].

[This corrects the article DOI: 10.1016/j.aninu.2022.08.017.].

Point-of-care testing for lysine concentration in swine serum via blue-emissive carbon dot-entrapped microfluidic chip.

Lysine is one of the essential amino acids and plays a vital role in the growth, development and health of pigs. Blood lysine concentration is a direct indication of lysine status; however, current methods can not satisfy the demands for rapid and on-site lysine concentration measurement of swine serum. Here, we developed blue-emissive nitrogen-doped carbon dots as a fluorescence probe for the determination of lysine with high fluorescence quantum yield, stability, sensitivity and specificity. The carbon dots were entrapped within hydrogel microstructures to fabricate microfluidic chips for rapid assay for lysine quantification. We further developed an imaging attachment to integrate the microfluidic chip and a smartphone into a portable point-of-care testing platform. This platform requires only 3 µL sample and has a linear detection range of 25 to 300 µmol/L with a limit of detection less than 16 µmol/L, which covers the normal range of lysine concentration in swine serum. We tested lysine concentration in swine serum using this platform with high accuracy, low sample consumption, and within 3 min. Together, these results may provide a rapid and portable platform for dynamic monitoring of swine lysine status and contribute to precise feed formula modulation with low-protein diet strategy.

Biomedical Application of Functional Materials in Organ-on-a-Chip.

The organ-on-a-chip (OOC) technology has been utilized in a lot of biomedical fields such as fundamental physiological and pharmacological researches. Various materials have been introduced in OOC and can be broadly classified into inorganic, organic, and hybrid materials. Although PDMS continues to be the preferred material for laboratory research, materials for OOC are constantly evolving and progressing, and have promoted the development of OOC. This mini review provides a summary of the various type of materials for OOC systems, focusing on the progress of materials and related fabrication technologies within the last 5 years. The advantages and drawbacks of these materials in particular applications are discussed. In addition, future perspectives and challenges are also discussed.

Simple patterned nanofiber scaffolds and its enhanced performance in immunoassay.

Cancer has become the leading cause of death worldwide; early diagnosis and treatment of cancers is critical for the survival of the patients. The concentration of cancer markers in easy-to-access biological fluids can provide great assistance in screening for occult primary cancers, distinguishing malignant from benign findings, determining prognosis and prediction for cancer patients. The multiplex detection technology of a panel of cancer markers can greatly increase the accuracy of disease diagnosis. Herein, we briefly fabricate a high-throughput micro-immunoassay based on the electrospun polystyrene (PS) substrates to improve detection sensitivity. The immunoassay was evaluated by analyzing three different cancer biomarkers (AFP, CEA, VEGF). For AFP, CEA, VEGF immunofluorescence assay, the LOD of assay conducted on electrospun PS substrates before or after plasma and the conventional PS substrates were 0.42, 0.10, 1.12 ng/mL, 0.57, 0.09, 1.24 ng/mL, and 159.75, 26.19, 385.59 pg/mL, respectively (P < 0.05). Due to the high porosity and large surface area-to-volume ratio which is the foremost merit of nanostructures, and the plasma treatment which make the hydrophobic PS nanofibers hydropholic, the nanofibers substrates showed sufficient retention of immunoassay functionality and high potential for capture molecules immobilization. Consequently, the immunofluorescence assay conducted on electrospun PS substrates could significantly enhance the sensitivity and limits of detection.

A 3D porous polymer monolith-based platform integrated in poly(dimethylsiloxane) microchips for immunoassay.

In this work, we demonstrate the immunocapture and on-line fluorescence immunoassay of protein and virus based on porous polymer monoliths (PPM) in microfluidic devices. Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [poly(GMA-co-EGDMA)] monoliths were successfully synthesized in the polydimethylsiloxane (PDMS) microfluidic channels by in situ UV-initiated free radical polymerization. After surface modification, PPM provides a high-surface area and specific affinity 3D substrate for immunoassays. Combining with well controlled microfluidic devices, the direct immunoassay of IgG and sandwich immunoassay of inactivated H1N1 influenza virus using 5 µL sample has been accomplished, with detection limits of 4 ng mL(-1) and less than 10 pg mL(-1), respectively. The enhanced detection sensitivity is due to both high surface area of PPM and flow-through design. The detection time was obviously decreased mainly due to the shortened diffusion distance and improved convective mass transfer inside the monolith, which accelerates the reaction kinetics between antigen and antibody. This work provides a novel microfluidic immunoassay platform with high efficiency thereby enabling fast and sensitive immunoassay.

Microchip-based immunoassays with application of silicon dioxide nanoparticle film.

Highly sensitive detection of proteins offers the possibility of early and rapid diagnosis of various diseases. Microchip-based immunoassay integrates the benefits from both immunoassays (high specificity of target sample) and microfluidics (fast analysis and low sample consumption). However, direct capture of proteins on bare microchannel surface suffers from low sensitivity due to the low capacity of microsystem. In this study, we demonstrated a microchip-based heterogeneous immunoassay using functionalized SiO(2) nanoparticles which were covalently assembled on the surface of microchannels via a liquid-phase deposition technique. The formation of covalent bonds between SiO(2) nanoparticles and polydimethylsiloxane substrate offered sufficient stability of the microfluidic surface, and furthermore, substantially enhanced the protein capturing capability, mainly due to the increased surface-area-to-volume ratio. IgG antigen and FITC-labeled anti-IgG antibody conjugates were adopted to compare protein-enrichment effect, and the fluorescence signals were increased by ~75-fold after introduction of functionalized SiO(2) nanoparticles film. Finally, a proof-of-concept experiment was performed by highly efficient capture and detection of inactivated H1N1 influenza virus using a microfluidic chip comprising highly ordered SiO(2) nanoparticles coated micropillars array. The detection limit of H1N1 virus antigen was 0.5 ng mL(-1), with a linear range from 20 to 1,000 ng mL(-1) and mean coefficient of variance of 4.71%.

Polymer monolith-integrated multilayer poly(dimethylsiloxane) microchip for online microextraction and capillary electrophoresis.

We reported the in situ synthesis and use of porous polymer monolith (PPM) columns in an integrated multilayer PDMS/glass microchip for microvalve-assisted on-line microextraction and microchip electrophoresis for the first time. Under the control of PDMS microvalves, the grafting of the microchannel surface and in situ photopolymerization of poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith in a defined zone were successfully achieved. Different factors including the surface grafting, polymerization time, PDMS elastic properties (ratio of oligomer/curing reagent) and UV intensity that affect the monolith synthesis in the PDMS microchannel were investigated and optimized. Dopamine, a model analyte, has been online microextracted, eluted, electrophoresized and electrochemically detected in the microchip, with a mean concentration enrichment factor of 80 (n=3). The results demonstrated that the PPM could be synthesized successfully in the PDMS microchip with a homogeneous structure and excellent mechanical properties. Furthermore, owing to the intrinsic character using PDMS in large-scale integrated microsystems, the implantation of PPM pretreatment units in PDMS microchips would make it possible to deal with complicated analytical processes in a high-throughput way.

Carbon and nitrogen composition and stable isotope as potential indicators of source and fate of organic matter in the salt marsh of the Changjiang Estuary, China.

Elemental (TOC, TN, C/N) and stable carbon and nitrogen isotopic (delta(13)C, delta(15)N) compositions were measured for surface sediments, three sediment vibrocores, plants, and suspended particulate matter (SPM) collected from salt marsh of the Changjiang Estuary. The purpose of this study is to characterize the sources of organic matter in sediments and to further elucidate the factors influencing the isotope signature in the salt marsh. Our results indicate that organic matter preserved in the sediments is predominantly controlled by the particulate organic matter in the Changjiang Estuary. The in situ contribution of marsh plants carbon to sediment organic matter is clearest in the high marsh, where the low delta(13)C of the plants (-28.1 per thousand) is reflected by a sediment delta(13)C (-24.7 per thousand) lower than values found for the low marsh and bare flat sediments (-23.4 per thousand and -23.0 per thousand, respectively). The effect of grain size on the spatial difference of isotope composition in the marsh sediments is insignificant, based on the observation that similar isotope values are found in different size particles, both for delta(13)C and delta(15)N. Nutrient utilization by plant assimilation, however, shows great impact on the surface sediment delta(15)N composition, due to the isotope fractionation. With extensive plant coverage and the consequent low surface water nitrate concentration, delta(15)N values of the high marsh surface sediments show (15)N enrichment.