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Coronavirus disease 2019 (COVID-19) pandemic is currently a serious global health threat. While conventional laboratory tests such as quantitative real-time polymerase chain reaction (qPCR), serology tests, and chest computerized tomography (CT) scan allow diagnosis of COVID-19, these tests are time-consuming and laborious, and are limited in resource-limited settings or developing countries. Point-of-care (POC) biosensors such as chip-based and paper-based biosensors are typically rapid, portable, cost-effective, and user-friendly, which can be used for COVID-19 in remote settings. The escalating demand for rapid diagnosis of COVID-19 presents a strong need for a timely and comprehensive review on the POC biosensors for COVID-19 that meet ASSURED criteria: Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end users. In the present review, we discuss the importance of rapid and early diagnosis of COVID-19 and pathogenesis of COVID-19 along with the key diagnostic biomarkers. We critically review the most recent advances in POC biosensors which show great promise for the detection of COVID-19 based on three main categories: chip-based biosensors, paper-based biosensors, and other biosensors. We subsequently discuss the key benefits of these biosensors and their use for the detection of antigen, antibody, and viral nucleic acids. The commercial POC biosensors for COVID-19 are critically compared. Finally, we discuss the key challenges and future perspectives of developing emerging POC biosensors for COVID-19. This review would be very useful for guiding strategies for developing and commercializing rapid POC tests to manage the spread of infections.Graphical abstract.

Cytokine secretion is a form of cellular communication that regulates a wide range of biological processes. A common approach for measuring cytokine secretion from single cells is to confine individual cells in arrays of nanoliter wells (nanowells) fabricated using polydimethylsiloxane. However, this approach cannot be easily integrated in standard microwell plates in order to take advantage of high-throughput infrastructure for automated and multiplexed analysis. Here, we used laser micropatterning to fabricate monolithic hydrogel nanowells inside wells in a microwell plate (microwells) using polyethylene glycol diacrylate (PEGDA). This approach produces high-aspect ratio nanowells that retain cells and beads during reagent exchange, enabling simultaneous profiling of single cell secretion and phenotyping via immunostaining. To limit contamination between nanowells, we used methylcellulose as a media additive to reduce diffusion distance. Patterning nanowells monolithically in microwells also dramatically increases density, providing ∼1200 nanowells per microwell in a microwell plate. Using this approach, we profiled IL-8 secretion from single MDA-MB-231 cells, which showed significant heterogeneity. We further profiled the polarization of THP-1 cells into M1 and M2 macrophages, along with their associated IL-1β and CCL-22 secretion profiles. These results demonstrate the potential to use this approach for high-throughput secretion and phenotype analysis on single cells.

Large bone defects are a major health concern worldwide. The conventional bone repair techniques (e.g., bone-grafting and Masquelet techniques) have numerous drawbacks, which negatively impact their therapeutic outcomes. Therefore, there is a demand to develop an alternative bone repair approach that can address the existing drawbacks. Bone tissue engineering involving the utilization of human mesenchymal stem cells (hMSCs) has recently emerged as a key strategy for the regeneration of damaged bone tissues. However, the use of tissue-engineered bone graft for the clinical treatment of bone defects remains challenging. While the role of mechanical loading in creating a bone graft has been well explored, the effects of mechanical loading factors (e.g., loading types and regime) on clinical outcomes are poorly understood. This review summarizes the effects of mechanical loading on hMSCs for bone tissue engineering applications. First, we discuss the key assays for assessing the quality of tissue-engineered bone grafts, including specific staining, as well as gene and protein expression of osteogenic markers. Recent studies of the impact of mechanical loading on hMSCs, including compression, perfusion, vibration and stretching, along with the potential mechanotransduction signalling pathways, are subsequently reviewed. Lastly, we discuss the challenges and prospects of bone tissue engineering applications.

Heterogeneity in cell populations poses a significant challenge for understanding complex cell biological processes. The analysis of cells at the single-cell level, especially single-cell RNA sequencing (scRNA-seq), has made it possible to comprehensively dissect cellular heterogeneity and access unobtainable biological information from bulk analysis. Recent efforts have combined scRNA-seq profiles with genomic or proteomic data, and show added value in describing complex cellular heterogeneity than transcriptome measurements alone. With the rising demand for scRNA-seq for biomedical and clinical applications, there is a strong need for a timely and comprehensive review on the scRNA-seq technologies and their potential biomedical applications. In this review, we first discuss the latest state of development by detailing each scRNA-seq technology, including both conventional and microfluidic technologies. We then summarize their advantages and limitations along with their biomedical applications. The efforts of integrating the transcriptome profile with highly multiplexed proteomic and genomic data are thoroughly reviewed with results showing the integrated data being more informative than transcriptome data alone. Lastly, the latest progress toward commercialization, the remaining challenges, and future perspectives on the development of scRNA-seq technologies are briefly discussed.

Cancer is one of the leading causes of death worldwide, and its incidence is steadily increasing. Although years of research have been conducted on cancer treatment, clinical treatment options for cancers are still limited. Animal cancer models have been widely used for studies of cancer therapeutics, but these models have been associated with many concerns, including inaccuracy in the representation of human cancers, high cost and ethical issues. Therefore, in vitro human cancer models are being developed quickly to fulfill the increasing demand for more relevant models in order to get a better knowledge of human cancers and to find novel treatments. This review summarizes the development of in vitro human cancer models for biomedical applications. We first review the latest development in the field by detailing various types of in vitro human cancer models, including transwell-based models, tumor spheroids, microfluidic tumor-microvascular systems and scaffold-based models. The advantages and limitations of each model, as well as their biomedical applications, are summarized, including therapeutic development, assessment of tumor cell migration, metastasis and invasion and discovery of key cancer markers. Finally, the existing challenges and future perspectives are briefly discussed.

Point-of-care biosensors are important tools developed to aid medical diagnosis and testing, food safety and environmental monitoring. Paper-based biosensors, especially nucleic acid-based lateral flow assays (LFA), are affordable, simple to produce and easy to use in remote settings. However, the sensitivity of such assays to infectious diseases has always been a restrictive challenge. Here, we have successfully electrospun polycaprolactone (PCL) on nitrocellulose (NC) membrane to form a hydrophobic coating to reduce the flow rate and increase the interaction rate between the targets and gold nanoparticles-detecting probes conjugates, resulting in the binding of more complexes to the capture probes. With this approach, the sensitivity of the PCL electrospin-coated test strip has been increased by approximately ten-fold as compared to the unmodified test strip. As a proof of concept, this approach holds great potential for sensitive detection of targets at point-of-care testing.

We demonstrate that polysiloxanes can be tuned to be partially hydrophilic for manipulating the fluidic flow in the pores of cotton thread-based microfluidic devices. A mixture of methanol and isopropanol was used as a diluent for siloxane precursor, which was included into the thread to enable rapid curing of polysiloxanes for fluidic control and enhance detection sensitivity. Interestingly, twelve-fold diluted polysiloxanes enabled desirable fluidic delay and optimum interaction between the targeted antigen and detection antibody-gold nanoparticles (dAb-AuNPs) in the thread-based immunoassay, generating more antigen-dAb-AuNP complexes that bound to the capture antibody (cAb) at the test zone and achieved signal enhancement (∼10-fold over unmodified device). The phenomenon of fluidic delay was evaluated by mathematical simulation, through which the fluidic movement on the polysiloxanes-coated region was observed and the simulation data was in agreement with the experimental data. This polysiloxanes-modified device could detect Salmonella enterica serotype Enteritidis (as a model analyte) in phosphate buffered saline, spiked whole milk, juice and lettuce with the detection limit of 500, 1000, 1000 and 5000 CFU/mL, respectively, which was comparable to or even more sensitive than the existing immunoassays. This work expands the application of polysiloxanes in the microfluidic devices for biomedical diagnosis, water quality monitoring, and food safety surveillance. usc Refereed/Peer-reviewed

In this study, a paper-based microfluidic enzyme-linked immunosorbent assay (ELISA) was developed as a screening system for rapid detection of clenbuterol, which is illegally used as a growth promoter for food-producing animals. The microfluidic paper-based analytical device (μPAD) was combined with ELISA and the intrinsic properties of paper allowed the entrapment of antibody through cellulosic fibres, validating to be an alternative to 96-well ELISA microplate for food safety monitoring. Detection of clenbuterol in milk was achieved by measuring the intensity of colour change that was proportional to the analyte concentration with a detection limit of 0.2 ppb. The μPAD effectively reduces the cost, volume of reagents, and time required to run ELISA for food sample testing. usc Refereed/Peer-reviewed

An outstanding amount of resources has been used in research on manipulation of human stem cells, especially mesenchymal stem cells (MSCs), for various clinical applications. However, human MSCs have not been fully utilized in clinical applications due to restrictions with regard to their certain biosafety and bioefficacy concerns, for example, genetic abnormality, tumor formation, induction of host immune response and failure of homing and engraftment. This review summarizes the biosafety and bioefficacy assessment of human MSCs in terms of genetic stability, tumorigenicity, immunogenicity, homing and engraftment. The strategies used to reduce the biosafety concerns and improve the bioefficacy of human MSCs are highlighted. In addition, the approaches that can be implemented to improve their biosafety and bioefficacy assessment are briefly discussed.

Nucleic acid testing (NAT) has been studied extensively in paper-based diagnostics, presenting a substantially higher sensitivity and specificity than immunoassays. Paper-based NAT provides an alternative to laborious, expensive and time-consuming conventional NAT. Recent advances in paper fabrication and modification technologies have made it possible to integrate all key steps of NAT (i.e., sample preparation, nucleic acid amplification and amplicon detection) into one single paper-based device, and are hence suitable for resource-poor settings. However, multiple challenges are yet to be addressed to translate the technologies into practical applications. In the present review, we discuss the current status and challenges in accomplishing each key step of NAT using low-cost paper substrates. We highlight the most recent advances, challenges and possible solutions in integrating all these steps into a compact paper-based device. We also review the latest progress towards commercialization and future perspectives on the development of an ideal sample-in-answer-out device.

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.

Yan Gong,1–3 Jie Hu,1,2 Jane Ru Choi,2 Minli You,1,2 Yamin Zheng,1,2 Bo Xu,4 Ting Wen,3 Feng Xu1,2 1The Key Laboratory of Biomedical Information Engineering of Ministry of Education, Department of Biomedical Engineering, School of Life Science and Technology, Xi’an Jiaotong University, 2Bioinspired Engineering and Biomechanics Center (BEBC), Xi’an Jiaotong University, 3Xi’an Diandi Biotech Company, 4School of Finance and Economics, Xi’an Jiaotong University, Xi’an, People’s Republic of China Abstract: Heart failure (HF) has become a major cause of morbidity and mortality with a significant global economic burden. Although well-established clinical tests could provide early diagnosis, access to these tests is limited in developing countries, where a relatively higher incidence of HF is present. This has prompted an urgent need for developing a cost-effective, rapid and robust diagnostic tool for point-of-care (POC) detection of HF. Lateral flow immunoassay (LFIA) has found widespread applications in POC diagnostics. However, the low sensitivity of LFIA limits its ability to detect important HF biomarkers (e.g., brain natriuretic peptide [BNP]) that are normally present in low concentration in blood. To address this issue, we developed an improved LFIA by optimizing the gold nanoparticle (GNP)–antibody conjugate conditions (e.g., the conjugate pH and the amount of added antibody), the diameter of GNP and the concentration of antibody embedded on the test line and modifying the structure of test strip. Through these improvements, the proposed test strip enabled the detection of BNP down to 0.1 ng/mL within 10–15min, presenting ~15-fold sensitivity enhancement over conventional lateral flow assay. We also successfully applied our LFIA in the analysis of BNP in human serum samples, highlighting its potential use for clinical assessment of HF. The developed LFIA for BNP could rapidly rule out HF with the naked eye, offering tremendous potential for POC test and personalized medicine. Keywords: heart failure, biomarker, colorimetric assays, personalized medicine

Lateral flow assays (LFAs) have found applications in clinical diagnostics, veterinary medicine, food safety, environmental monitoring, bio-defence, drug abuse, etc . However, conventional LFAs with single test zone for one analyte (sLFA) show qualitative, positive/negative results (that are usually not so accurate for decision-making) and suffer from the hook effect (that easily induces false negative results). In this study, a modified LFA with multiple test zones for one analyte (mLFA) is developed for detection of nucleic acid showing two methods to interpret assay results. One is the sum of detection signals of test zones, which exhibits a stable and broader detection range compared with sLFA. The other is the pattern of test zones that is presented is correlated to the concentration of analyte, facilitating semi-quantitative detection without the aid of a reader or analyzer.

Conventional methods for extraction of DNA are expensive, time-consuming and tedious. To overcome these limitations, a paper-based DNA extraction device was developed that incorporates sponge-based buffer storage, a paper-based valve and channels of different length to autonomously direct the reagent and sample to the Fusion 5 disk for DNA capturing. With this device, DNA can be extracted within 2 min from only 30 μL samples of whole blood, serum, breast cancer cell, saliva, sputum and bacterial suspension. The device can also extract Hepatitis B Virus DNA from clinical blood samples and after quantification shows a detection limit as low as 104 copies⋅mL−1. This highlights its potential use in future diagnostics. The performance of the device was similar to that of the commercial QIAamp DNA micro kits and the FTA card. In our perception, this simple, inexpensive, portable and disposable device holds great promise in terms of POC testing in resource-poor settings.

Since the invention of polymerase chain reaction (PCR) in 1985, PCR has played a significant role in molecular diagnostics for genetic diseases, pathogens, oncogenes and forensic identification. In the past three decades, PCR has evolved from end-point PCR, through real-time PCR, to its current version, which is the absolute quantitive digital PCR (dPCR). In this review, we first discuss the principles of all key steps of dPCR, i.e., sample dispersion, amplification, and quantification, covering commercialized apparatuses and other devices still under lab development. We highlight the advantages and disadvantages of different technologies based on these steps, and discuss the emerging biomedical applications of dPCR. Finally, we provide a glimpse of the existing challenges and future perspectives for dPCR.

Cryopreservation is the only existing method of storage of human adipose-derived stem cells (ASCs) for clinical use. However, cryopreservation has been shown to be detrimental to ASCs, particularly in term of cell viability. To restore the viability of cryopreserved ASCs, it is proposed to culture the cells in a hypoxic condition. To this end, we aim to investigate the effect of hypoxia on the cryopreserved human ASCs in terms of not only cell viability, but also their growth and stemness properties, which have not been explored yet. In this study, human ASCs were cultured under four different conditions: fresh (non-cryopreserved) cells cultured in 1) normoxia (21% O2) and 2) hypoxia (2% O2) and cryopreserved cells cultured in 3) normoxia and 4) hypoxia. ASCs at passage 3 were subjected to assessment of viability, proliferation, differentiation, and expression of stemness markers and hypoxia-inducible factor-1 alpha (HIF-1α). We found that hypoxia enhances the viability and the proliferation rate of cryopreserved ASCs. Further, hypoxia upregulates HIF-1α in cryopreserved ASCs, which in turn activates chondrogenic genes to promote chondrogenic differentiation. In conclusion, hypoxic-preconditioned cryopreserved ASCs could be an ideal cell source for cartilage repair and regeneration.

Human adipose-derived mesenchymal stem cells (hASCs) are an ideal cell source for regenerative medicine due to their capabilities of multipotency and the readily accessibility of adipose tissue. They have been found residing in a relatively low oxygen tension microenvironment in the body, but the physiological condition has been overlooked in most studies. In light of the escalating need for culturing hASCs under their physiological condition, this review summarizes the most recent advances in the hypoxia effect on hASCs. We first highlight the advantages of using hASCs in regenerative medicine and discuss the influence of hypoxia on the phenotype and functionality of hASCs in terms of viability, stemness, proliferation, differentiation, soluble factor secretion, and biosafety. We provide a glimpse of the possible cellular mechanism that involved under hypoxia and discuss the potential clinical applications. We then highlight the existing challenges and discuss the future perspective on the use of hypoxic-treated hASCs.

Nucleic acid testing (NAT) has been widely used for disease diagnosis, food safety control and environmental monitoring. At present, NAT mainly involves nucleic acid extraction, amplification and detection steps that heavily rely on large equipment and skilled workers, making the test expensive, time-consuming, and thus less suitable for point-of-care (POC) applications. With advances in paper-based microfluidic technologies, various integrated paper-based devices have recently been developed for NAT, which however require off-chip reagent storage, complex operation steps and equipment-dependent nucleic acid amplification, restricting their use for POC testing. To overcome these challenges, we demonstrate a fully disposable and integrated paper-based sample-in-answer-out device for NAT by integrating nucleic acid extraction, helicase-dependent isothermal amplification and lateral flow assay detection into one paper device. This simple device allows on-chip dried reagent storage and equipment-free nucleic acid amplification with simple operation steps, which could be performed by untrained users in remote settings. The proposed device consists of a sponge-based reservoir and a paper-based valve for nucleic acid extraction, an integrated battery, a PTC ultrathin heater, temperature control switch and on-chip dried enzyme mix storage for isothermal amplification, and a lateral flow test strip for naked-eye detection. It can sensitively detect Salmonella typhimurium, as a model target, with a detection limit of as low as 102 CFU ml−1 in wastewater and egg, and 103 CFU ml−1 in milk and juice in about an hour. This fully disposable and integrated paper-based device has great potential for future POC applications in resource-limited settings.

A volumetric meter chip was developed for quantitative point-of-care (POC) analysis of bovine catalase, a bioindicator of bovine mastitis, in milk samples. The meter chip displays multiplexed quantitative results by presenting the distance of ink bar advancement that is detectable by the naked eye. The meter chip comprises a poly(methyl methacrylate) (PMMA) layer, a double-sided adhesive (DSA) layer and a glass slide layer fabricated by the laser-etching method, which is typically simple, rapid (∼3 min per chip), and cost effective (∼$0.2 per chip). Specially designed "U shape" reaction cells are covered by an adhesive tape that serves as an on-off switch, enabling the simple operation of the assay. As a proof of concept, we employed the developed meter chip for the quantification of bovine catalase in raw milk samples to detect catalase concentrations as low as 20 μg/mL. The meter chip has great potential to detect various target analytes for a wide range of POC applications.

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.

Electrospun polycaprolactone (PCL) nanofibers have emerged as a promising material in diverse biomedical applications due to their various favorable features. However, their application in the field of biosensors such as point-of-care lateral flow assays (LFA) has not been investigated. The present study demonstrates the use of electrospun PCL nanofibers as a reaction membrane for LFA. Electrospun PCL nanofibers were treated with NaOH solution for different concentrations and durations to achieve a desirable flow rate and optimum detection sensitivity in nucleic acid-based LFA. It was observed that the concentration of NaOH does not affect the physical properties of nanofibers, including average fiber diameter, average pore size and porosity. However, interestingly, a significant reduction of the water contact angle was observed due to the generation of hydroxyl and carboxyl groups on the nanofibers, which increased their hydrophilicity. The optimally treated nanofibers were able to detect synthetic Zika viral DNA (as a model analyte) sensitively with a detection limit of 0.5 nM. Collectively, the benefits such as low-cost of fabrication, ease of modification, porous nanofibrous structures and tunability of flow rate make PCL nanofibers a versatile alternative to nitrocellulose membrane in LFA applications. This material offers tremendous potential for a broad range of point-of-care applications.

Background: Molecularly Imprinted Polymers (MIPs), a type of biomimetic materials have attracted considerable interest owing to their cost-effectiveness, good physiochemical stability, favorable specificity and selectivity for target analytes, and long shelf life. These materials are able to mimic natural recognition entities, including biological receptors and antibodies, providing a versatile platform to achieve the desirable functionality for various biomedical applications. Objective: In this review article, we introduce the most recent development of MIPs to date. We first highlight the advantages of using MIPs for a broad range of biomedical applications. We then review their various methods of synthesis along with their latest progress in biomedical applications, including biosensing, drug delivery, cell imaging and drug discovery. Lastly, the existing challenges and future perspectives of MIPs for biomedical applications are briefly discussed. Conclusion: We envision that MIPs may be used as potential materials for diverse biomedical applications in the near future.

Dengue endemic is a serious healthcare concern in tropical and subtropical countries. Although well-established laboratory tests can provide early diagnosis of acute dengue infections, access to these tests is limited in developing countries, presenting an urgent need to develop simple, rapid, and robust diagnostic tools. Point-of-care (POC) devices, particularly paper-based POC devices, are typically rapid, cost-effective and user-friendly, and they can be used as diagnostic tools for the prompt diagnosis of dengue at POC settings. Here, we review the importance of rapid dengue diagnosis, current dengue diagnostic methods, and the development of paper-based POC devices for diagnosis of dengue infections at the POC.

Cryopreservation represents an efficient way to preserve human mesenchymal stem cells (hMSCs) at early culture/passage, and allows pooling of cells to achieve sufficient cells required for off-the-shelf use in clinical applications, e.g. cell-based therapies and regenerative medicine. To fully apply cryopreserved hMSCs in a clinical setting, it is necessary to evaluate their biosafety, e.g. chromosomal abnormality and tumourigenic potential. To date, many studies have demonstrated that cryopreserved hMSCs display no chromosomal abnormalities. However, the tumourigenic potential of cryopreserved hMSCs has not yet been evaluated. In the present study, we cryopreserved human adipose-derived mesenchymal stem cells (hASCs) for 3 months, using a slow freezing method with various cryoprotective agents (CPAs), followed by assessment of the tumourigenic potential of the cryopreserved hASCs after thawing and subculture. We found that long-term cryopreserved hASCs maintained normal levels of the tumour suppressor markers p53, p21, p16 and pRb, hTERT, telomerase activity and telomere length. Further, we did not observe significant DNA damage or signs of p53 mutation in cryopreserved hASCs. Our findings suggest that long-term cryopreserved hASCs are at low risk of tumourigenesis. These findings aid in establishing the biosafety profile of cryopreserved hASCs, and thus establishing low hazardous risk perception with the use of long-term cryopreserved hASCs for future clinical applications. Copyright © 2016 John Wiley & Sons, Ltd.

The need to have a better and safer culture condition for expansion of human mesenchymal stem cells (MSCs) is crucial particularly to prevent infection and immune rejection. This is normally associated with the use of animal-based serum in the culture media for cell expansion. The aim of this study is to investigate alternative culture conditions which may provide better and safer environment for cell growth. In the present study, human adipose-derived stem cells (ASCs) at passage 3 were subjected to treatment in 4 conditions: (1) 21 % O2 with fetal bovine serum (FBS), (2) 21 % O2 without FBS, (3) 2 % O2 with FBS and (4) 2 % O2 without FBS followed by subsequent analysis of their phenotype, viability and functionality. We observed that ASCs cultured in all conditions present no significant phenotypic changes. It was found that ASCs cultured in 2 % O2 without serum showed an increase in viability and growth to a certain extent when compared to those cultured in 21 % O2 without serum. However, ASCs cultured in 2 % O2 without serum displayed a relatively low adipogenic and osteogenic potential. On the other hand, interestingly, there was a positive enhancement in chondrogenic differentiation of ASCs cultured in 21 % O2 without serum. Our findings suggest that different culture conditions may be suitable for different indications. In summary, ASCs cultured in serum-free condition can still survive, proliferate and undergo subsequent adipogenic, osteogenic and chondrogenic differentiation. Therefore, FBS is feasible to be excluded for culture of ASCs, which avoids clinical complications.

Lateral flow assays (LFAs) have been extensively explored in nucleic acid testing (NAT) for medical diagnostics, food safety analysis and environmental monitoring. However, the amount of target nucleic acid in a raw sample is usually too low to be directly detected by LFAs, necessitating the process of amplification. Even though cost-effective paper-based amplification techniques have been introduced, they have always been separately performed from LFAs, hence increasing the risk of reagent loss and cross-contaminations. To date, integrating paper-based nucleic acid amplification into colorimetric LFA in a simple, portable and cost-effective manner has not been introduced. Herein, we developed an integrated LFA with the aid of a specially designed handheld battery-powered system for effective amplification and detection of targets in resource-poor settings. Interestingly, using the integrated paper-based loop-mediated isothermal amplification (LAMP)-LFA, we successfully performed highly sensitive and specific target detection, achieving a detection limit of as low as 3 × 10(3) copies of target DNA, which is comparable to the conventional tube-based LAMP-LFA in an unintegrated format. The device may serve in conjunction with a simple paper-based sample preparation to create a fully integrated paper-based sample-to-answer diagnostic device for point-of-care testing (POCT) in the near future.

Nucleic acid testing (NAT), as a molecular diagnostic technique, including nucleic acid extraction, amplification and detection, plays a fundamental role in medical diagnosis for timely medical treatment. However, current NAT technologies require relatively high-end instrumentation, skilled personnel, and are time-consuming. These drawbacks mean conventional NAT becomes impractical in many resource-limited disease-endemic settings, leading to an urgent need to develop a fast and portable NAT diagnostic tool. Paper-based devices are typically robust, cost-effective and user-friendly, holding a great potential for NAT at the point of care. In view of the escalating demand for the low cost diagnostic devices, we highlight the beneficial use of paper as a platform for NAT, the current state of its development, and the existing challenges preventing its widespread use. We suggest a strategy involving integrating all three steps of NAT into one single paper-based sample-to-answer diagnostic device for rapid medical diagnostics in the near future.

Black phosphorus (BP), also known as phosphorene, has attracted recent scientific attention since its first successful exfoliation in 2014 owing to its unique structure and properties. In particular, its exceptional attributes, such as the excellent optical and mechanical properties, electrical conductivity and electron-transfer capacity, contribute to its increasing demand as an alternative to graphene-based materials in biomedical applications. Although the outlook of this material seems promising, its practical applications are still highly challenging. In this review article, we discuss the unique properties of BP, which make it a potential platform for biomedical applications compared to other 2D materials, including graphene, molybdenum disulphide (MoS2),tungsten diselenide (WSe2) and hexagonal boron nitride (h-BN). We then introduce various synthesis methods of BP and review its latest progress in biomedical applications, such as biosensing, drug delivery, photo acoustic imaging and cancer therapies (i.e., photothermal and photodynamic therapies). Lastly, the existing challenges and future perspective of BP in biomedical applications are briefly discussed. usc Refereed/Peer-reviewed

Today, articular cartilage damage is a major health problem, affecting people of all ages. The existing conventional articular cartilage repair techniques, such as autologous chondrocyte implantation (ACI), microfracture, and mosaicplasty, have many shortcomings which negatively affect their clinical outcomes. Therefore, it is essential to develop an alternative and efficient articular repair technique that can address those shortcomings. Cartilage tissue engineering, which aims to create a tissue-engineered cartilage derived from human mesenchymal stem cells (MSCs), shows great promise for improving articular cartilage defect therapy. However, the use of tissue-engineered cartilage for the clinical therapy of articular cartilage defect still remains challenging. Despite the importance of mechanical loading to create a functional cartilage has been well demonstrated, the specific type of mechanical loading and its optimal loading regime is still under investigation. This review summarizes the most recent advances in the effects of mechanical loading on human MSCs. First, the existing conventional articular repair techniques and their shortcomings are highlighted. The important parameters for the evaluation of the tissue-engineered cartilage, including chondrogenic and hypertrophic differentiation of human MSCs are briefly discussed. The influence of mechanical loading on human MSCs is subsequently reviewed and the possible mechanotransduction signaling is highlighted. The development of non-hypertrophic chondrogenesis in response to the changing mechanical microenvironment will aid in the establishment of a tissue-engineered cartilage for efficient articular cartilage repair.

Adipose-derived stem cells (ASCs) have been found residing in a native microenvironment with low oxygen tension (i.e hypoxia) in human body. Oxygen tension plays a crucial role in regulating their function. The aim of this study is to investigate the effects of hypoxia on proliferation and survival rate of ASCs. Human ASCs were cultured at 21% O2 (normoxia) or 2% O2 (hypoxia) for up to three passages. We found that ASCs displayed a higher proliferation rate under hypoxia as compared to normoxia. The viability of ASCs was higher in hypoxia than normoxia without altering their characteristics. These properties might be correlated with the up-regulation of HIF-1α and the increased transcriptional and translational level of growth factors, VEGF-A and bFGF. Taken together, 2% oxygen tension has been suggested as an ideal condition for expansion of ASCs efficiently, where large number of cells can be produced over a short period of time for clinical use.

Human mesenchymal stem cells (hMSCs), a type of adult stem cells that hold great potential in clinical applications (e.g., regenerative medicine and cell-based therapy) due to their ability to differentiate into multiple types of specialized cells and secrete soluble factors which can initiate tissue repair and regulate immune response. hMSCs need to be expanded in vitro or cryopreserved to obtain sufficient cell numbers required for clinical applications. However, long-term in vitro culture-expanded hMSCs may raise some biosafety concerns (e.g., chromosomal abnormality and malignant transformation) and compromised functional properties, limiting their use in clinical applications. To avoid those adverse effects, it is essential to cryopreserve hMSCs at early passage and pool them for off-the-shelf use in clinical applications. However, the existing cryopreservation methods for hMSCs have some notable limitations. To address these limitations, several approaches have to be taken in order to produce healthy and efficacious cryopreserved hMSCs for clinical trials, which remains challenging to date. Therefore, a noteworthy amount of resources has been utilized in research in optimization of the cryopreservation methods, development of freezing devices, and formulation of cryopreservation media to ensure that hMSCs maintain their therapeutic characteristics without raising biosafety concerns following cryopreservation. Biobanking of hMSCs would be a crucial strategy to facilitate clinical applications in the future.

In recent years, paper-based point-of-care testing (POCT) has been widely used in medical diagnostics, food safety and environmental monitoring. However, a high-cost, time-consuming and equipment-dependent sample pretreatment technique is generally required for raw sample processing, which are impractical for low-resource and disease-endemic areas. Therefore, there is an escalating demand for a cost-effective, simple and portable pretreatment technique, to be coupled with the commonly used paper-based assay (e.g. lateral flow assay) in POCT. In this review, we focus on the importance of using paper as a platform for sample pretreatment. We firstly discuss the beneficial use of paper for sample pretreatment, including sample collection and storage, separation, extraction, and concentration. We highlight the working principle and fabrication of each sample pretreatment device, the existing challenges and the future perspectives for developing paper-based sample pretreatment technique.

With advances in point-of-care testing (POCT), lateral flow assays (LFAs) have been explored for nucleic acid detection. However, biological samples generally contain complex compositions and low amounts of target nucleic acids, and currently require laborious off-chip nucleic acid extraction and amplification processes (e.g., tube-based extraction and polymerase chain reaction (PCR)) prior to detection. To the best of our knowledge, even though the integration of DNA extraction and amplification into a paper-based biosensor has been reported, a combination of LFA with the aforementioned steps for simple colorimetric readout has not yet been demonstrated. Here, we demonstrate for the first time an integrated paper-based biosensor incorporating nucleic acid extraction, amplification and visual detection or quantification using a smartphone. A handheld battery-powered heating device was specially developed for nucleic acid amplification in POC settings, which is coupled with this simple assay for rapid target detection. The biosensor can successfully detect Escherichia coli (as a model analyte) in spiked drinking water, milk, blood, and spinach with a detection limit of as low as 10-1000 CFU mL(-1), and Streptococcus pneumonia in clinical blood samples, highlighting its potential use in medical diagnostics, food safety analysis and environmental monitoring. As compared to the lengthy conventional assay, which requires more than 5 hours for the entire sample-to-answer process, it takes about 1 hour for our integrated biosensor. The integrated biosensor holds great potential for detection of various target analytes for wide applications in the near future.