Flow-S: A Field-Deployable Device with Minimal Hands-On Effort to Concentrate and Quantify Schistosoma Circulating Anodic Antigen (CAA) from Large Urine Volumes

A laboratory-based lateral flow (LF) test that utilizes up-converting reporter particles (UCP) for ultrasensitive quantification of Schistosoma circulating anodic antigen (CAA) in urine is a well-accepted test to identify active infection. However, this UCP-LF CAA test requires sample pre-treatment steps not compatible with field applications. Flow, a new low-cost disposable, allows integration of large-volume pre-concentration of urine analytes and LF detection into a single field-deployable device. We assessed a prototype Flow-Schistosoma (Flow-S) device with an integrated UCP-LF CAA test strip, omitting all laboratory-based steps, to enable diagnosis of active Schistosoma infection in the field using urine. Flow-S is designed for large-volume (5-20 mL) urine, applying passive paper-based filtration and antibody-based CAA concentration. Samples tested for schistosome infection were collected from women of reproductive age living in a Tanzania region where S. haematobium infection is endemic. Fifteen negative and fifteen positive urine samples, selected based on CAA levels quantified in paired serum, were analyzed with the prototype Flow-S. The current Flow-S prototype, with an analytical lower detection limit of 1 pg CAA/mL, produced results correlated with the laboratory-based UCP-LF CAA test. Urine precipitates occurred in frozen banked samples and affected accurate quantification; however, this should not occur in fresh urine. Based on the findings of this study, Flow-S appears suitable to replace the urine pre-treatment required for the laboratory-based UCP-LF CAA test, thus allowing true field-based applications with fresh urine samples. The urine precipitates observed with frozen samples, though less important given the goal of testing fresh urines, warrant additional investigation to evaluate methods for mitigation. Flow-S devices permit testing of pooled urine samples with applications for population stratified testing. A field test with fresh urine samples, a further optimized Flow-S device, and larger statistical power has been scheduled.

"Scentsor": A Whole-Cell Yeast Biosensor with an Olfactory Reporter for Low-Cost and Equipment-Free Detection of Pharmaceuticals

Portable and inexpensive analytical tools are required to monitor pharmaceutical quality in technology limited settings including low- and middle-income countries (LMICs). Whole cell yeast biosensors have the potential to help meet this need. However, most of the readouts for yeast biosensors require expensive equipment or reagents. To overcome this challenge, we have designed a yeast biosensor that produces a unique scent as a readout. This inducible scent biosensor, or "scentsor", does not require the user to administer additional reagents for reporter development and utilizes only the user's nose to be "read". In this Letter, we describe a scentsor that is responsive to the hormone estradiol (E2). The best estimate threshold (BET) for E2 detection with a panel of human volunteers (n = 49) is 39 nM E2 (15 nM when "non-smellers" are excluded). This concentration of E2 is sensitive enough to detect levels of E2 that would be found in dosage forms. This paper provides evidence that scent has the potential for use in portable yeast biosensors as a readout, particularly for use in LMICs.

Dopamine-Based Paper Analytical Device for Truly Equipment-Free and Naked-Eye Biosensing Based on the Target-Initiated Catalyzed Oxidation

The development of low cost, portable, and disposable biosensors for equipment-free and naked-eye biosensing is in eager demand for their widespread application in biomedical field, but it is still a challenge. Herein, we propose a novel paper analytical device (PAD) for truly equipment-free and naked-eye biosensing using dopamine as the chromogenic agent based on target-initiated catalyzed oxidation reaction. The dopamine-functionalized PAD (DPAD) possesses a significant three-dimensional net structure, excellent hydrophilicity, and unique response toward G-quadruplex DNAs against other DNAs, benefiting the bio/chemo reaction occurrence to assay target biomolecules. In light of the exceptional properties, the fabricated DPAD was applied in the analysis of Dam MTase through target-triggered exponential isothermal amplification. The recognition and methylation of H1 by Dam MTase contribute to formation of abundant hemin/G-quadruplexes, which catalyze oxidation of dopamine into dopachrome and reduce the dopamine amount on the DPAD surface. In comparison with the case in which Dam MTase is absent, an evident deep pink signal originating from dopachrome is observed directly by the naked eye and relied on Dam MTase concentrations. Therefore, truly equipment-free and naked-eye detection of Dam MTase is achieved with a detection limit of 1.46 U/mL. The fabricated DPAD not only achieves Dam MTase-visualized detection but also permits the accurate determination of other analytes by varying recognizable DNA's sequences, thus offering a universal biosensor and depicting significant potential for widespread applications in biomedical field.

Facile and Equipment-Free Data Encryption and Decryption by Self-Encrypting Pt(II) Complex

Luminescence switching materials are vital to various data security-related techniques, including data encryption-decryption. Here, we report a family of pseudopolymorphs based on a diimine-platinum(II) complex, Pt(Me₃SiC≡CbpyC≡CSiMe₃)(C≡CC₆H₄Br-3)₂ (1), and systematically studied the influence of stacking modes on luminescence switching behaviors. Upon exposure to heat or tetrahydrofuran vapor, these pseudopolymorphs exhibit unusual stacking mode-intervened luminescence switching (SMILS) property that non-columnar and quasi-columnar pseudopolymorphs undergo single- and multi-step conversion processes, respectively, to the same non-columnar products. Systematic studies revealed that the unique SMILS behavior is caused by the existence of stable intermediate products as well as different conversion processes of pseudopolymorphs with distinct stacking modes. Such a new property leads to the self-encryption function of 1, which is very important for improving the existing data encryption-decryption technique. On this basis, we developed a facile, reusable, equipment-free technique with 1 as the only starting material and realized data encryption-decryption successfully.