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Sweet taste detection is of great significance in fields of disease prevention, food safety inspection, and drug regulation. In this study, a novel biomimetic sensor was constructed for sweet taste detection by compositing graphene oxide, hemin, and 3-aminophenylboronic acid (APBA). First, optimal fabrication of the sensor was investigated by comparing different composition proportions of graphene oxide and APBA functionalized hemin in saccharide measurements. Then, typical substances of natural sugars (i.e., glucose and fructose) and artificial sweeteners (i.e., saccharin and aspartame) were measured with the sensor through optical absorption spectroscopy. The spectra displayed apparent but different absorbance changes in the presence of those two kinds of saccharides, showing different sensing mechanisms of the biomimetic sensor for sugars and sweeteners like sweet receptors. Finally, dose-dependent and specific responses of the sensor were observed by comparing with other taste substances. The results suggested that the sensor can detect and distinguish natural sugars and artificial sweeteners in a biomimetic way. The research provided a low-cost, long-lifetime, and efficient approach for sweet taste detection, indicating its promising applications in fields such as food and beverage analysis.

Wireless, passive, low-cost and portable detection systems are in high demand for environment monitoring, food safety and health care diagnosis. Among them smartphone-based sensing systems are receiving special attention with the worldwide popularity of smartphones. Over the past decade, many devices, including a large number of smartphones in today’s marketplace, are integrated with near field communication (NFC) modules. Leveraging the worldwide ubiquity of these devices, we developed wireless and passive NFC tag sensors based on flexible and low-cost NFC tags for biochemical sensing. NFC-enabled smartphone was used to wirelessly power the sensors and receive the detection results through inductive coupling. By adopting rheostats in the resonant circuits of the sensors, we easily achieved accurate semi-quantitative detection of different analytes constructed sensor arrays. The results demonstrated that the tag sensors could be used to discriminate gases at part-per-million concentrations and analytes in solution such as ions and bacteria in different concentration ranges. Thus, the wireless, passive, low-cost and flexible NFC tag sensors unfolded new dimensions for biochemical sensing with smartphones.

Thrombin is an important kind of proteases that can cleavage specific peptide bonds and plays a crucial role in numerous diseases, which leads to large amounts of efforts on its detection. In this study, a novel peptide self-assembled biosensor was developed based on gold nanoparticles functionalized graphene oxide (GO) for specific detection of thrombin. Through sulfhydryl design, peptides containing thrombin cleavage sites could self-assemble with the nanocomposites of the graphene material and gold particles, which brought the biosensor unique optoelectronic properties and high biological sensitivity to transduce bio-molecular interactions into optical signals. Spectroscopic measurements were carried out in the presence of thrombin to observe an increase of the absorption peak at ∼528 nm and a decrease of the absorbance at wavelength larger than 600 nm. The biosensor showed a linear dose-dependence and stable response to thrombin. And with a 528–680 nm absorbance ratio as the sensitive detection parameter, the self-assembled biosensor exhibited high sensitivity and specificity for the thrombin detection. Thus, it revealed convenient and sensitive detection abilities for protease of thrombin, indicating a promising prospect for other related proteases, such as matrix metalloproteinases to cancer related diseases.

Last decade has seen a growing trend toward smartphone-based biochemical sensing systems. Meanwhile, flexible electrochemical sensing devices like wristbands, patches, and tattoos have been widely developed for in situ detections of analytes in accessible biofluids. For these devices, the connectivity with smartphone and the flexibility of the whole device are hard to achieve at the same time, due to the need for rigid batteries or wired connections. Here, a smartphone-based battery-free and flexible electrochemical patch is developed for real-time calcium and chloride ions detections in various biofluids. The patch is integrated with near field communication (NFC) module, on-site signal processing circuitry, and an all-printed stretchable electrode array which can maintain stable conductivity during stretching, without the need for serpentine designs. The device enables wireless power harvesting, on-site signal processing, and wireless data transmission capabilities. NFC-enabled smartphones can wirelessly power the patch and get the detection results through inductive coupling between antennas. The calcium and chloride sensors showed good sensitivity, repeatability, selectivity, and stability in quantitative detections of target ions. Ex situ measurements in serum, urine, tear, and sweat demonstrated good consistency with specialized instrument. Real-time on-body sweat analysis with the patch was also performed, which further indicated the usability and stability of the device in wearable applications. This platform provides a battery-free, wireless, and flexible solution for smartphone-based electrochemical sensing systems, which can be applied to rapid analysis of various biofluids.