Manipulating the hydrophobicity of DNA as a universal strategy for visual biosensing

Visual Biosensing with Specific Liquid-Based Interface Behaviors

Liquid-based interface behaviors at micro/nano or even smaller scales induced by biomolecules take us into a fascinating realm, fostering a deeper understanding and innovation in visual biosensing. This biosensing technology, grounded in specific liquid-based interface behaviors, redefines how diseases can be detected, monitored, and diagnosed in resource-limited settings, providing rapid, cost-effective, and self-testing solutions to the current healthcare landscape. To date, the technology has witnessed significant advancements in visual sensing, driven by diverse liquid-based materials, advanced nanomanufacturing techniques, and a profound understanding of interface-material interactions. In this Perspective, we discuss and elucidate the interface biosensing mechanisms arising from three types, including liquid-solid, liquid-liquid, and liquid-gas interfaces, and we provide insights into the challenges and future development of visual biosensing applications.

Nano-Structural Superwetting Surfaces for Highly Reliable On-Site Detection of Bisphenol A

In the domain of big data geographic screening for environmental pollutants, the expeditious dissemination of testing results to environmental investigation professionals is pivotal in facilitating comprehensive analysis and the implementation of more efficacious strategies for managing environmental issues. However, this endeavor can prove to be particularly arduous when conducting examinations in remote, resource-scarce rural areas and field environments, where deficient infrastructure often emerges as the principal impediment to unimpeded environmental monitoring. Therefore, the development of a reliable and portable monitoring strategy with the ability to analyze large amounts of data is highly required. Here, a deep-learning (DL)-assisted portable sensing strategy was developed based on thermal and pH dual-responsive nano-structural superwetting surfaces, for highly reliable, quick, and field monitoring of environmental pollutants. In our experiment, bisphenol A (BPA) was selected as the representative pollute. The achieved limit of detection, attaining a remarkably low value of 1.05 μM, unequivocally adhered to stringent international testing standards for evaluating the migration of BPA in thermal paper. Based on a DL image classification algorithm, highly precise predictions regarding the migration of BPA concentration were achieved, with an accuracy rate exceeding 99%. Furthermore, it successfully facilitated automated and exceedingly reliable monitoring of the migration of BPA from thermal paper within the principal provinces of thermal paper production in China. This strategy engenders the potential to establish correlations between environmental pollutant concentrations in specific regions and the prevalence of certain human ailments.

Emerging open-channel droplet arrays for biosensing

Open-channel droplet arrays have attracted much attention in the fields of biochemical analysis, biofluid monitoring, biomarker recognition and cell interactions, as they have advantages with regard to miniaturization, parallelization, high-throughput, simplicity and accessibility. Such droplet arrays not only improve the sensitivity and accuracy of a biosensor, but also do not require sophisticated equipment or tedious processes, showing great potential in next-generation miniaturized sensing platforms. This review summarizes typical examples of open-channel microdroplet arrays and focuses on diversified biosensing integrated with multiple signal-output approaches (fluorescence, colorimetric, surface-enhanced Raman scattering (SERS), electrochemical, etc.). The limitations and development prospects of open-channel droplet arrays in biosensing are also discussed with regard to the increasing demand for biosensors.

A portable and partitioned DNA hydrogel chip for multitarget detection

A DNA hydrogel, owing to its dual properties of liquid and solid, is considered to be an ideal material for constructing biosensors that can integrate the advantages of both wet chemistry and dry chemistry. Nevertheless, it has struggled to cope with the demands of high-throughput analysis. A partitioned and chip-based DNA hydrogel is a potential avenue to achieve this, but currently remains a formidable challenge. Here, we developed a portable and partitioned DNA hydrogel chip that can be used for multitarget detection. The partitioned and surface-immobilized DNA hydrogel chip was formed by inter-crosslinking amplification by incorporating target-recognizing fluorescent aptamer hairpins into multiple rolling circle amplification products, which can achieve portable and simultaneous detection of multiple targets. This approach expands the application of semi-dry chemistry strategies, which can realize high throughput and point of care testing (POCT) of different targets, improving the development of hydrogel-based bioanalysis and providing new potential solutions for biomedical detection.

Bioinspired liquid-infused surface for biomedical and biosensing applications

Nature always inspires us to develop advanced materials for diverse applications. The liquid-infused surface (LIS) inspired by Nepenthes pitcher plants has aroused broad interest in fabricating anti-biofouling materials over the past decade. The infused liquid layer on the solid substrate repels immiscible fluids and displays ultralow adhesion to various biomolecules. Due to these fascinating features, bioinspired LIS has been applied in biomedical-related fields. Here, we review the recent progress of LIS in bioengineering, medical devices, and biosensing, and highlight how the infused liquid layer affects the performance of medical materials. The prospects for the future trend of LIS are also presented.

Molecular Visual Sensing, Boolean Logic Computing, and Data Security Using a Droplet-Based Superwetting Paradigm

Inspired by information processing and logic operations of life, many artificial biochemical systems have been designed for applications in molecular information processing. However, encoding the binary synergism between matter, energy, and information in a superwetting system remains challenging. Herein, a superwetting paradigm was proposed for multifunctional applications including molecular visual sensing and data security on a superhydrophobic surface. A Triton X-100-encapsulated gelatin (TeG) hydrogel was prepared and selectively decomposed by trypsin, releasing the surfactant to decrease the surface tension of a droplet. Integrating the droplet with the superhydrophobic surface, the superwetting behavior was utilized for visual detection and information encoding. Interestingly, the proposed TeG hydrogel can function as an artificial gelneuron for molecular-level logic computing, where the combination of matters (superhydrophobic surface, trypsin, and leupeptin) acts as inputs to interact with energy (liquid surface tension and solid surface energy) and information (binary character), resulting in superwettability transitions (droplet surface tension, contact angle, rolling angle, and bounce) as outputs. Impressively, the TeG gelneuron can be further developed as molecular-level double cryptographic steganography to encode, encrypt, and hide specific information (including the maze escape route and content of the classical literature) due to its programmability, stimuli responsive ability, and droplet concealment. This study will encourage the development of advanced molecular paradigms and their applications, such as superwetting visual sensing, molecular computing, interaction, and data security.

TiO2 with Confined Water Boosts Ultrahigh Selective Enrichment of Phosphorylated Proteins

In the selective enrichment of phosphorylated proteins (PPs) from biological samples, the non-phosphorylated proteins (NPPs) adhered onto enrichment adsorbents due to the hydrophobic interaction, resulting in poor selectivity and low recovery of target PPs. Herein, superhydrophilic TiO₂-coated porous SiO₂ microspheres are prepared and boost remarkable selectivity toward standard PP spiked with 2000 mass-fold NPP interference. The outstanding performance of the superhydrophilic microspheres is attributed to the coordination interaction between TiO₂ and PPs, and the confined water layer generated from superhydrophilicity avoids the irreversible adsorption of NPPs by keeping NPP inner hydrophobic regions in a compact structure, which is verified by single molecule force spectroscopy, circular dichroism, and quartz crystal microbalance. This strategy for enrichment is expected to solve the challenge in proteomics and sheds light on the interactions between biomolecules and superwettability.

Superwettable Biosensor for Disease Biomarker Detection

Bioinspired superwettable materials have aroused wide interests in recent years for their promising application fields from service life to industry. As one kind of emerging application, the superwettable surfaces used to fabricate biosensors for the detection of disease biomarkers, especially tumor biomarkers, have been extensively studied. In this mini review, we briefly summarized the sensing strategy for disease biomarker detection based on superwettable biosensors, including fluorescence, electrochemistry, surface-enhanced Raman scattering, and visual assays. Finally, the challenges and direction for future development of superwettable biosensors are also discussed.

Bio-inspired Superwettable Surface for the Detection of Cancer Biomarker: A Mini Review

Inspired by nature, superwettable material-based biosensors have aroused wide interests due to their potential in cancer biomarker detection. This mini review mainly summarized the superwettable materials as novel biosensing substrates for the development of evaporation-induced enrichment-based signal amplification and visual biosensing method. Biosensing applications based on the superhydrophobic surfaces, superwettable micropatterned surfaces, and slippery lubricant-infused porous surfaces for various cancer biomarker detections were described in detail. Finally, an insight of remaining challenges and perspectives of superwettable biosensor is proposed.

A semi-dry chemistry hydrogel-based smart biosensing platform for on-site detection of metal ions

Balancing operability and performance has long been a focus of research in bioanalysis and biosensing. In this work, between the traditional wet chemistry and dry chemistry, we develop a semi-dry smart biosensing platform with favourable operability and performance for metal ions detection. This platform is based on the integration of a stimuli-responsive hydrogel with intelligent image recognition. The hydrogel consists of agarose as a matrix and well-designed fluorescent DNA probes as response elements. Target metal ions in a test sample can diffuse into the hydrogel and activate the DNA probes, outputting fluorescence signals for intelligent imaging. In this way, sensitive and convenient detection of metal ions such as potassium ions (K+) and mercury ions (Hg2+) can be achieved without the assistance of huge instruments and professional workers. The detection limits for K+ and Hg2+ are 0.34 mM and 5.6 nM, respectively. Detection of ions in serum and lake water is also available. Moreover, the hydrogel-based biosensing platform exhibits favorable selectivity, anti-degradation ability, and long-term stability. High-throughput testing can be also achieved by punching multiple test microwells in a single piece of hydrogel. The concept and successful practice of a semi-dry chemistry-based strategy make up for the shortcomings of wet chemistry and dry chemistry, and provide a promising approach for on-site testing.

Novel Protease-Free Long-Lasting Chemiluminescence System Based on the Dox-ABEI Chimeric Magnetic DNA Hydrogel for Ultrasensitive Immunoassay

Most of chemiluminescence (CL) substrates exhibit the flash-type light emission. Therefore, the long-lasting CL system is always the crown in the field of CL-based analysis methodology. In this work, we constructed a Dox-ABEI chimeric magnetic DNA hydrogel (MDH) as a novel protease-free long-lasting CL reaction system. The functional MDH can transform flash-type ABEI/H₂O₂/CO²⁺ reaction into a glow-type CL system because of its block effect on delaying the diffusion rate of co-reactants, making the CL reaction gradually occur. More importantly, the functional MDH possessed the advantages of biocompatibility and controllability and could be well-designed to incorporate different biosensing strategies. Subsequently, we established a functional MDH-based long-lasting CL immunoassay system for ultrasensitive and highly specific detection of d-dimer and fibrin degradation products (FDPs). The designed CL immunoassay can detect d-dimer and FDP down to 53.7 and 31.6 fg/mL, respectively, with a wide line ranging from 100 fg/mL to 100 ng/mL, which was superior to the previously reported CL biosensing strategies. Moreover, benefiting from the magnetic separation of MDH and excellent CL performance, the developed immunoassaying method was successfully applied in the detection of clinical samples, which showed a close correlation with clinical reference technology. Thus, this functional MDH proved to be an excellent long-lasting CL system and a potential technical platform for clinical bioanalysis applications.