Electrochemical-based remote biomarker monitoring: Toward Internet of Wearable Things in telemedicine.

Internet of Wearable Things (IoWT) will be a major breakthrough for remote medical monitoring. In this scenario, wearable biomarker sensors have been developing not only to diagnose point-of-care (POC) of diseases, but also to continuously manage them. On-body tracking of biomarkers in biofluids is regarded as a proper substitution of conventional biomarker sensors for dynamic sampling and analyzing due to their high sensitivity, conformability, and affordability, creating ever-rising the market demand for them. In a wireless body area network (WBAN), data is captured from all sensors on the body to a smartphone/laptop, and sent the sensed data to a cloud for storing, processing, and retrieving, and ultimately displayed the data on custom applications (Apps). Wearable IoT biomarker sensors are used for early diseases diagnosis and continuous monitoring in developing countries in which people hardly access to healthcare systems. In this review, we aim to highlight a wide range of wearable electrochemical biomarker sensors, accompanied by microfluidics for continuous sampling, which will pave the way toward developing wearable IoT biomarker sensors to track health status. The current challenges and future perspective in skin-conformal biomarker sensors will be discussing their potential applicability for IoWT in cloud-based telemedicine.

Phytochemicals toward Green (Bio)sensing.

Because of numerous inherent and unique characteristics of phytochemicals as bioactive compounds derived from plants, they have been widely used as one of the most interesting nature-based compounds in a myriad of fields. Moreover, a wide variety of phytochemicals offer a plethora of fascinating optical and electrochemical features that pave the way toward their development as optical and electrochemical (bio)sensors for clinical/health diagnostics, environmental monitoring, food quality control, and bioimaging. In the current review, we highlight how phytochemicals have been tailored and used for a wide variety of optical and electrochemical (bio)sensing and bioimaging applications, after classifying and introducing them according to their chemical structures. Finally, the current challenges and future directions/perspective on the optical and electrochemical (bio)sensing applications of phytochemicals are discussed with the goal of further expanding their potential applications in (bio)sensing technology. Regarding the advantageous features of phytochemicals as highly promising and potential biomaterials, we envisage that many of the existing chemical-based (bio)sensors will be replaced by phytochemical-based ones in the near future.

A nanocellulose-based colorimetric assay kit for smartphone sensing of iron and iron-chelating deferoxamine drug in biofluids.

The current work describes the development of a "nanopaper-based analytical device (NAD)", through the embedding of curcumin in transparent bacterial cellulose (BC) nanopaper, as a colorimetric assay kit for monitoring of iron and deferoxamine (DFO) as iron-chelating drug in biological fluids such as serum blood, urine and saliva. The iron sensing strategy using the developed assay kit is based on the decrease of the absorbance/color intensity of curcumin-embedded in BC nanopaper (CEBC) in the presence of Fe(III), due to the formation of Fe(III)-curcumin complex. On the other hand, releasing of Fe(III) from Fe(III)-CEBC upon addition of DFO as an iron-chelating drug, due to the high affinity of this drug to Fe(III) in competition with curcumin, which leads to recovery of the decreased absorption/color intensity of Fe(III)-CEBC, is utilized for selective colorimetric monitoring of this drug. The absorption/color changes of the fabricated assay kit as output signal can be monitored by smartphone camera or by using a spectrophotometer. The results of our developed sensor agreed well with the results from a clinical reference method for determination of Fe(III) concentration in human serum blood samples, which revealed the clinical applicability of our developed assay kit. Taken together, regarding the advantageous features of the developed sensor as an easy-to-use, non-toxic, disposable, cost-effective and portable assay kit, along with those of smartphone-based sensing, it is anticipated that this sensing bioplatform, which we name lab-on-nanopaper, will find utility for sensitive, selective and easy diagnosis of iron-related diseases (iron deficiency and iron overload) and therapeutic drug monitoring (TDM) of iron-chelating drugs in clinical analysis as well.

Spectrophotometric and visual determination of zoledronic acid by using a bacterial cell-derived nanopaper doped with curcumin.

A nanopaper-based analytical device (NAD) is described for a colorimetric metal-complexing indicator-displacement assay (M-IDA) for zoledronic acid (ZA). Bacterial cellulose nanopaper was doped with curcumin to obtain a chemosensor on which hydrophilic test zones were patterned via laser printing of hydrophobic walls. The color intensity of the test zones decreases in the presence of Fe(III) due to the formation of Fe(III)-curcumin complex. However, upon addition of ZA, Fe(III) ions preferably binds ZA. Subsequently, the color of the zone changes from light yellow to dark yellow. The changes in the absorption (measured at 427 nm) and of the color of the test stripe can be monitored visually, by using a digital camera, or by a spectrophotometer. Under optimal conditions, the analytical signals increase linearly in the 0.01-100 µM ZA concentration range, and the detection limits are 8.8 and 8.0 nM for smartphone and spectrophotometer-based methods, respectively. The method was employed to the determination of ZA in (spiked) urine, serum, saliva, and in pharmaceutical samples. Graphical abstract Schematic representation of a nanopaper-based analytical device based on curcumin-doped BC nanopaper (CDBC) integrated with smartphone for metal-complexing indicator-displacement assay of zoledronic acid (ZA). High affinity of ZA to Fe(III) on the NAD/CDBC leads to color change.

A paper-based optical probe for chromium by using gold nanoparticles modified with 2,2'-thiodiacetic acid and smartphone camera readout.

A paper based analytical device is presented for the determination of Cr(III) and Cr(VI) using gold nanoparticles (AuNPs) modified with 2,2'-thiodiacetic acid. The modified AuNPs were characterized using UV-Vis spectrophotometry, Fourier transform infrared, dynamic light scattering, zeta potential, energy dispersive spectroscopy and transmission electron microscopy. Cr(III) ions induce the aggregation of the modified AuNPs, and the color of the nanoprobe changes from red to blue. This can be detected visually, or by colorimetry, or with a camera. No interference is observed in the presence of 19 other cations and anions. Cr(VI) (chromate) can be determined by after reduction to Cr(III) by using ascorbic acid and then quantified total Cr(III). The concentration of Cr(VI) is obtained by subtracting the concentration of Cr(III) from that of total chromium. Under optimal conditions, the ratio of the absorbances measured at 670 (blue) and 522 (red) increases linearly in the 1.0 nM to 22.1 µM chromium concentration range, with 0.66 nM (0.034 ppb) limit of detection (LOD) in solution. In case of the paper device, the linear range extends from 1.0 nM to 0.1 mM, and the LOD is 0.64 nM (0.033 ppb). The method was applied to the determination of chromium in spiked water, urine and dilutes human plasma, and results were confirmed by GF-AAS analysis. This method is highly selective, fast and portable, requires minimum volume of reagents and samples and no washing steps. Graphical abstract A paper based analytical device is presented for determination of Cr(III) and Cr(VI) using gold nanoparticles modified with 2,2'-thiodiacetic acid. In paper optical probe, linear range and limit of detection are 1.0 nM to 0.1 mM and 0.64 nM, respectively. The method was applied to the determination of total chromium in spiked water, urine and dilutes human plasma, and results were confirmed by GF-AAS analysis.

QSRR Models for Kováts' Retention Indices of a Variety of Volatile Organic Compounds on Polar and Apolar GC Stationary Phases Using Molecular Connectivity Indexes.

Quantitative structure-retention relationship (QSRR) approaches, based on molecular connectivity indices are useful to predict the gas chromatography of Kováts relative retention indices (GC-RRIs) of 132 volatile organic compounds (VOCs) on different 12 (4 apolar and 8 polar) stationary phases (C(67), C(103), C(78), C(∞), POH, TTF, MTF, PCL, PBR, TMO, PSH and PCN) at 130 °C. Full geometry optimization based on Austin model 1 semi-empirical molecular orbital method was carried out. The sets of 30 molecular descriptors were derived directly from the topological structures of the compounds from DRAGON program. By means of the final variable selection method, which is elimination selection stepwise regression algorithms, three optimal descriptors were selected to develop a QSRR model to predict the RRI of organic compounds on each stationary phase with a correlation coefficient between 0.9378 and 0.9673 and a leave-one-out cross-validation correlation coefficient between 0.9325 and 0.9653. The root mean squares errors over different 12 phases were within the range of 0.0333-0.0458. Furthermore, the accuracy of all developed models was confirmed using procedures of Y-randomization, external validation through an odd-even number and division of the entire dataset into training and test sets. A successful interpretation of the complex relationship between GC RRIs of VOCs and the chemical structures was achieved by QSRR. The three connectivity indexes in the models are also rationally interpreted, which indicated that all organic compounds' RRI was precisely represented by molecular connectivity indexes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1365/s10337-010-1741-4) contains supplementary material, which is available to authorized users.