Optical Detection of Heparin in Whole Blood Samples Using Nanosensors Embedded in an Agarose Hydrogel

Agarose Gel-Coated Nanochannel Biosensor for Detection of Prostate-Specific Antigen in Unprocessed Whole Blood Samples

Solid-state nanopore/nanochannel biosensors have rapidly advanced due to their high sensitivity, label-free detection, and fast response. However, detecting biomarkers directly in complex biological environments, particularly whole blood, remains challenging because of nonspecific protein adsorption and nanopore/nanochannel clogging. Here, a DNA aptamer functionalized nanochannel biosensor is developed with excellent antifouling properties, achieved by coating the nanochannel surface with agarose gel. This gel coating effectively mitigates fouling in diverse biological environments while maintaining comparable sensitivity to uncoated nanochannels for detecting prostate-specific antigen (PSA) in buffer solutions within 20 min. The biosensor exhibits a detection limit of 1 ng mL-1 for PSA in human serum, matching the performance of commercial enzyme-linked immunosorbent assay (ELISA) kits. Importantly, it successfully differentiates whole blood samples from prostate cancer patients and healthy individuals. The superior antifouling behavior is attributed to the electrically neutral, highly hydrophilic nature, and porous structure of the agarose gel, which prevents the adsorption of large biomolecules while facilitating the diffusion of PSA for aptamer-based capture. This DNA aptamer functionalized nanochannel biosensor with agarose gel coating offers reliable protein detection in complex biological environments, showing great promise in biomedical applications.

A label-free fluorescent-hydrogel sensor for heparin detection in diluted whole blood

Heparin is a widely used blood anticoagulant and its monitoring in blood is essential during surgery. Unavoidable interference factors such as blood color and luminescence can interfere with the fluorescence visualization of heparin. Herein, we found a ratiometric fluorescence probe consisting of SYBR green and cresyl violet responsive to heparin mainly based on electrostatic interactions. A simple sensor was further embedded in an agarose hydrogel, exhibiting an obvious color change from orange to green without complex pretreatment of blood, which overcomes the susceptibility of fluorescence sensors toward biological samples.

Direct Detection of Tobacco Mosaic Virus in Infected Plants with SERS-Sensing Hydrogels

The impact of plant pathogens on global crop yields is a major societal concern. The current agricultural diagnostic paradigm involves either visual inspection (inaccurate) or laboratory molecular tests (burdensome). While field-ready diagnostic methods have advanced in recent years, issues remain with detection of presymptomatic infections, multiplexed analysis, and requirement for in-field sample processing. To overcome these issues, we developed surface-enhanced Raman scattering (SERS)-sensing hydrogels that detect pathogens through simple contact with a leaf. In this work, we developed a novel reagentless SERS sensor for the detection of tobacco mosaic virus (TMV) and embedded it in an optimized hydrogel material to produce sensing hydrogels. To test the diagnostic application of our sensing hydrogels, we demonstrate their use to detect TMV infection in tobacco plants. This technology has the potential to shift the current agricultural diagnostic paradigm by offering a field-deployable tool for presymptomatic and multiplexed molecular identification of pathogens.

Near-Infrared Fluoride Sensing Nano-Optodes and Distance-Based Hydrogels Containing Aluminum-Phthalocyanine

Fluoride ions are highly relevant in environmental and biological sciences, and there is a very limited number of established fluoride chemical sensors. Previous fluoride-selective optodes were demonstrated with metal-porphyrin as the ionophore and required a chromoionophore for optical signal transduction. We demonstrate here novel optical fluoride sensing with nano-optodes containing an aluminum-phthalocyanine complex (AlClPc) as the single active sensing component, simplifying the conventional ion-selective optodes approach. The fluoride nano-optodes were interrogated in the absorbance and fluorescence modes in the near-infrared region, with absorption around 725 nm and emission peaks at 720 and 800 nm, respectively. The nano-optodes exhibited a lower detection limit around 0.1 μM and good selectivity over a range of common anions including ClO4-, Cl-, Br-, I-, SO42-, NO3-, and AcO-. Furthermore, the nano-optodes were physically entrapped in agarose hydrogels to allow distance-based point-of-care testing (POCT) applications. The 3D networks of the agarose hydrogel were able to filter off large particulates in the samples without stopping fluoride ions to reach the nano-optodes. The fluoride concentrations in real samples including river water, mineral water, and groundwater were successfully determined with the distance-based sensing hydrogel, and the results agreed well with those from commercial fluoride electrodes. Therefore, the results in this work lay the groundwork for the optical detection of fluoride in environmental samples without very sophisticated sample manipulation.

Photoacoustic Chemical Imaging Sodium Nano-Sensor Utilizing a Solvatochromic Dye Transducer for In Vivo Application

Sodium has many vital and diverse roles in the human body, including maintaining the cellular pH, generating action potential, and regulating osmotic pressure. In cancer, sodium dysregulation has been correlated with tumor growth, metastasis, and immune cell inhibition. However, most in vivo sodium measurements are performed via Na23 NMR, which is handicapped by slow acquisition times, a low spatial resolution (in mm), and low signal-to-noise ratios. We present here a plasticizer-free, ionophore-based sodium-sensing nanoparticle that utilizes a solvatochromic dye transducer to circumvent the pH cross-sensitivity of most previously reported sodium nano-sensors. We demonstrate that this nano-sensor is non-toxic, boasts a 200 μM detection limit, and is over 1000 times more selective for sodium than potassium. Further, the in vitro photoacoustic calibration curve presented demonstrates the potential of this nano-sensor for performing the in vivo chemical imaging of sodium over the entire physiologically relevant concentration range.