The research interest in wearable sensors has tremendously increased in recent years. Amid the different biosensors, electrochemical biosensors are unparalleled and ideal for the design and manufacture of such flexible and wearable sensors because of their various benefits, including convenient operation, quick response, portability, and inherent miniaturization. A number of studies on flexible and wearable electrochemical biosensors have been reported in recent years for invasive/non-invasive and real-time monitoring of biologically relevant molecules such as glucose, lactate, dopamine, cortisol, and antigens. To attain this, novel two-dimensional nanomaterials and their hybrids, various substrates, and detection methods have been explored to fabricate flexible conductive platforms that can be used to develop flexible electrochemical biosensors. In particular, there are many advantages associated with the advent of two-dimensional materials, such as light weight, high stretchability, high performance, and excellent biocompatibility, which offer new opportunities to improve the performance of wearable electrochemical sensors. Therefore, it is urgently required to study wearable/flexible electrochemical biosensors based on two-dimensional nanomaterials for health care monitoring and clinical analysis. In this review, we described recently reported flexible electrochemical biosensors based on two-dimensional nanomaterials. We classified them into specific groups, including enzymatic/non-enzymatic biosensors and affinity biosensors (immunosensors), recent developments in flexible electrochemical immunosensors based on polymer and plastic substrates to monitor biologically relevant molecules. This review will discuss perspectives on flexible electrochemical biosensors based on two-dimensional materials for the clinical analysis and wearable biosensing devices, as well as the limitations and prospects of the these electrochemical flexible/wearable biosensors.
Graphical abstract
Emergency obstetric care (EmOC) within primary health care systems requires a linked referral system to be effective in reducing maternal death. This systematic review aimed to summarize evidence on the proportion of referrals between institutions during pregnancy and delivery, and the factors affecting referrals, in India. We searched 6 electronic databases, reviewed four regional databases and repositories, and relevant program reports from India published between 1994 and 2013. All types of study or reports (except editorials, comments and letters) which reported on institution-referrals (out-referral or in-referral) for obstetric care were included. Results were synthesized on the proportion and the reasons for referral, and factors affecting referrals. Of the 11,346 articles identified by the search, we included 232 articles in the full text review and extracted data from 16 studies that met our inclusion criteria Of the 16, one was RCT, seven intervention cohort (without controls), six cross-sectional, and three qualitative studies. Bias and quality of studies were reported. Between 25% and 52% of all pregnancies were referred from Sub-centres for antenatal high-risk, 14% to 36% from nurse run delivery or basic EmOC centres for complications or emergencies, and 2 to 7% were referred from doctor run basic EmOC centres for specialist care at comprehensive EmOC centres. Problems identified with referrals from peripheral health centres included low skills and confidence of staff, reluctance to induce labour, confusion over the clinical criteria for referral, non-uniform standards of care at referral institutions, a tendency to by-pass middle level institutions, a lack of referral communication and supervision, and poor compliance. The high proportion of referrals from peripheral health centers reflects the lack of appropriate clinical guidelines, processes, and skills for obstetric care and referral in India. This, combined with inadequate referral communication and low compliance, is likely to contribute to gaps and delays in the provision of emergency obstetric care.
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