Capillary blood for point-of-care testing

<p>Clinically, blood sample analysis has been widely used for health monitoring. In hospitals, arterial and venous blood are utilized to detect various disease biomarkers. However, collection methods are invasive, painful, may result in injury and contamination, and skilled workers are required, making these methods unsuitable for use in a resource-limited setting. In contrast, capillary blood is easily collected by a minimally invasive procedure and has excellent potential for use in point-of-care (POC) health monitoring. In this review, we first discuss the differences among arterial blood, venous blood, and capillary blood in terms of the puncture sites, components, sample volume, collection methods, and application areas. Additionally, we review the most recent advances in capillary blood-based commercial products and microfluidic instruments for various applications. We also compare the accuracy of microfluidic-based testing with that of laboratory-based testing for capillary blood-based disease diagnosis at the POC. Finally, we discuss the challenges and future perspectives for developing capillary blood-based POC instruments.</p

Polydimethylsiloxane-Paper Hybrid Lateral Flow Assay for Highly Sensitive Point-of-Care Nucleic Acid Testing

In nucleic acid testing (NAT), gold nanoparticle (AuNP)-based lateral flow assays (LFAs) have received significant attention due to their cost-effectiveness, rapidity, and the ability to produce a simple colorimetric readout. However, the poor sensitivity of AuNP-based LFAs limits its widespread applications. Even though various efforts have been made to improve the assay sensitivity, most methods are inappropriate for integration into LFA for sample-to-answer NAT at the point-of-care (POC), usually due to the complicated fabrication processes or incompatible chemicals used. To address this, we propose a novel strategy of integrating a simple fluidic control strategy into LFA. The strategy involves incorporating a piece of paper-based shunt and a polydimethylsiloxane (PDMS) barrier to the strip to achieve optimum fluidic delays for LFA signal enhancement, resulting in 10-fold signal enhancement over unmodified LFA. The phenomena of fluidic delay were also evaluated by mathematical simulation, through which we found the movement of fluid throughout the shunt and the tortuosity effects in the presence of PDMS barrier, which significantly affect the detection sensitivity. To demonstrate the potential of integrating this strategy into a LFA with sample-in-answer-out capability, we further applied this strategy into our prototype sample-to-answer LFA to sensitively detect the Hepatitis B virus (HBV) in clinical blood samples. The proposed strategy offers great potential for highly sensitive detection of various targets for wide application in the near future

<i>In Situ</i> Normoxia Enhances Survival and Proliferation Rate of Human Adipose Tissue-Derived Stromal Cells without Increasing the Risk of Tumourigenesis

<div><p>Adipose tissue-derived stromal cells (ASCs) natively reside in a relatively low-oxygen tension (i.e., hypoxic) microenvironment in human body. Low oxygen tension (i.e., <i>in situ</i> normoxia), has been known to enhance the growth and survival rate of ASCs, which, however, may lead to the risk of tumourigenesis. Here, we investigated the tumourigenic potential of ASCs under their physiological condition to ensure their safe use in regenerative therapy. Human ASCs isolated from subcutaneous fat were cultured in atmospheric O₂ concentration (21% O₂) or <i>in situ</i> normoxia (2% O₂). We found that ASCs retained their surface markers, tri-lineage differentiation potential, and self-renewal properties under <i>in situ</i> normoxia without altering their morphology. <i>In situ</i> normoxia displayed a higher proliferation and viability of ASCs with less DNA damage as compared to atmospheric O₂ concentration. Moreover, low oxygen tension significantly up-regulated VEGF and bFGF mRNA expression and protein secretion while reducing the expression level of tumour suppressor genes p16, p21, p53, and pRb. However, there were no significant differences in ASCs telomere length and their relative telomerase activity when cultured at different oxygen concentrations. Collectively, even with high proliferation and survival rate, ASCs have a low tendency of developing tumour under <i>in situ</i> normoxia. These results suggest 2% O₂ as an ideal culture condition for expanding ASCs efficiently while maintaining their characteristics.</p></div

In situ normoxia lowered the expression of tumour suppressor genes and maintained both telomerase activity and TRF length of ASCs.

<p>In situ normoxia displayed lower expression levels of p53, p21, p16 and pRb (A) as compared to atmospheric O2 concentration. There were no significant difference between both groups on their telomerase activity (B) and mean TRF length (C). Data are presented as mean ± SEM. * indicates p < 0.05 relative to atmospheric O2 concentration.</p

In situ normoxia enhanced the expansion rate of ASCs without changing their morphology and self-renewal properties.

<p>Cells maintained fibroblast-like appearance on day 3, 7 and 10 of culture. The density of the cells was remarkably increased under in situ normoxia, magnification 100x (A). In situ normoxia maintained the number of CFU-F. Macroscopic examination showed the single colonies of ASCs, representing the population which exhibits the self-renewal properties of MSC (B). Growth curve of ASCs (C) showed an increased rate of cell proliferation under in situ normoxia. Population doubling time (D) of ASCs was significantly lower under in situ normoxia than in atmospheric O2 concentration. Cell cycle analysis showed the percentage of ASCs in S-phase was higher under in situ normoxia as compared to atmospheric O2 concentration (E). Data shown represent as mean ± SEM. * indicates p < 0.05 relative to atmospheric O2 concentration.</p

In situ normoxia enhanced the survival of ASCs by reducing the rate of apoptosis and DNA damage.

<p>In situ normoxia showed a higher percentage of viable cells with lower numbers of apoptotic and necrotic cells than atmospheric O2 concentration (A). A representative figure of DNA showed more cells without comet tails were observed under in situ normoxia, magnification 100x. Arrows show the comet tails. ASCs cultured under in situ normoxia displayed a significantly lower tail length, percentage of tail DNA and tail moment in comparison with ASCs under atmospheric O2 concentration (B). Each data represents mean ± SEM. * indicates p < 0.05 relative to atmospheric O2 concentration.</p