Liquid Crystal-Infused Porous Polymer Surfaces: A "Slippery" Soft Material Platform for the Naked-Eye Detection and Discrimination of Amphiphilic Species

Slippery Liquid-Infused Porous Surfaces Infused with Thermotropic Liquid Crystals Enable Droplet-Based, Naked-Eye Reporting of Changes in Peptide Structure and Protease Activity

We report the design of liquid crystal-infused "slippery" liquid-infused porous surfaces (LC-SLIPS) that permit naked-eye detection and reporting on the structural differences and activities of peptides and protease enzymes in aqueous media. We demonstrate that small (e.g., 20 μL) droplets of aqueous solutions placed in contact with LC-SLIPS exhibit sliding behaviors that vary substantially with the concentrations, structures, and physicochemical properties (e.g., hydrophobicity) of model amphiphilic β- and α/β-peptides dissolved within them. These large differences in sliding times permit naked-eye detection and discrimination of changes in peptide structure, including side-chain substitution, end group structure, backbone structure, and charge that correlate with differences in peptide amphiphilicity. We demonstrate further that LC-SLIPS can be used to monitor other biochemical processes, including digestion by proteases, that affect changes in the structures of amphiphilic peptides and can, thus, be used to develop novel, naked-eye assays that can report sensitively on enzymatic activity. As proof of concept, we show that large and visually observable changes in droplet sliding resulting from the degradation of a model peptide can be used to detect the presence of trypsin in aqueous solutions at levels as low as 12.5 ng/mL. That result, in turn, served as the basis of an LC-SLIPS-based assay that can be used to detect clinically relevant concentrations (from 25 to 25,000 ng/mL) of trypsinogen, a well-established biomarker for acute pancreatitis, in samples of synthetic urine. This "sliding" assay is conceptually straightforward and requires only visual monitoring and/or a hand-held stopwatch for readout, highlighting the potential for low-cost, point-of-care diagnostics applications. Overall, our results demonstrate the ability of LC-SLIPS to capture and report structural information relevant to other therapeutic properties and applications of amphiphilic peptides that could also be useful in the context of drug design and screening.

Sprayable Biocide-Free Polyurethane Paint that Reduces Biofouling and Facilitates Removal of Pathogenic Bacteria from Surfaces

The ability to prevent bacterial adhesion on surfaces and to facilitate the removal of bacteria once they have already contaminated or colonized a surface is important in a broad range of fundamental and applied contexts. The work reported here sought to characterize the physicochemical properties of a family of biocide-free hydrophobic polyurethane coatings containing polysiloxane segments and evaluate their ability to mitigate bacterial fouling and/or facilitate subsequent surface cleaning after exposure to pathogenic bacteria. We developed benchtop microbiological assays to characterize surface fouling and subsequent removal of bacteria after repeated (i) short-term intermittent physical contact with and (ii) longer-term continuous flow-based contact with liquid growth media containing either S. aureus or E. coli, two common Gram-positive or Gram-negative bacterial pathogens, respectively. Characterization of fouled and cleaned surfaces using fluorescence microscopy and standard agar-based plaque assays revealed significant differences in both reductions in initial fouling and subsequent cleanability after gentle rinsing with water. These differences correlated to differences in the surface properties of these materials (e.g., hydrophobicity and contact angle hysteresis), with coatings exhibiting lower contact angle hysteresis generally having the greatest antibiofouling and easy-to-clean properties. Our results suggest that these biocide-free, siloxane-containing polyurethane-based clearcoat materials show significant promise for the mitigation of surface fouling and bacterial adhesion, which could prove useful in a range of commercial applications, including in "high touch" environments where microbial contamination is endemic.

Core-Labeled Reverse Micelle-Based Supramolecular Solvents for Assisted Quick and Sensitive Determination of Amitriptyline in Wastewater

In recent years, the issue of pharmaceutical contaminants in water bodies has emerged as a significant environmental concern owing to the potential negative impacts on both aquatic ecosystems and human health. Consequently, the development of efficient and eco-friendly methods for their determination and removal is of paramount importance. In this context, the development of a surfactant ensemble sensor has been explored for hard-to-sense amphiphilic drug, i.e., amitriptyline. Herein, a pyrene-based amphiphile chemoreceptor was synthesized and characterized through various spectroscopic techniques such as 1H, 13C NMR, single-crystal XRD, FTIR, and ES-mass spectrometry. Then, dodecanoic acid (DA) and a pyrene-based receptor in a THF/water solvent system were used to generate reverse micelle-based self-aggregates of SUPRAS (SUPRAmolecular Solvent). The structural aspects, such as morphology and size, along with the stability of the SUPRAS aggregates were unfolded through spectroscopic and microscopic insights. The present investigation describes a synergistic approach that combines the unique properties of premicellar concentration of supramolecular solvent with the promising potential of pyrene-based receptor for enhanced amitriptyline extraction with simultaneous determination from water (LOD = 12 nM). To evaluate the effectiveness of the developed aggregates in real-world scenarios, experiments were conducted to determine the sensing efficiency among various pharmaceutical pollutants commonly found in water sources. The results reveal that the synergistic nanoensemble exhibits remarkable sensing ability, toward the amitriptyline (AMT) drug outperforming conventional methods.

Decoding Optical Responses of Contact-Printed Arrays of Thermotropic Liquid Crystals Using Machine Learning: Detection and Reporting of Aqueous Amphiphiles with Enhanced Sensitivity and Selectivity

Surfactants and other amphiphilic molecules are used extensively in household products, industrial processes, and biological applications and are also common environmental contaminants; as such, methods that can detect, sense, or quantify them are of great practical relevance. Aqueous emulsions of thermotropic liquid crystals (LCs) can exhibit distinctive optical responses in the presence of surfactants and have thus emerged as sensitive, rapid, and inexpensive sensors or reporters of environmental amphiphiles. However, many existing LC-in-water emulsions require the use of complicated or expensive instrumentation for quantitative characterization owing to variations in optical responses among individual LC droplets. In many cases, the responses of LC droplets are also analyzed by human inspection, which can miss subtle color or topological changes encoded in LC birefringence patterns. Here, we report an LC-based surfactant sensing platform that takes a step toward addressing several of these issues and can reliably predict concentrations and types of surfactants in aqueous solutions. Our approach uses surface-immobilized, microcontact-printed arrays of micrometer-scale droplets of thermotropic LCs and hierarchical convolutional neural networks (CNNs) to automatically extract and decode rich information about topological defects and color patterns available in optical micrographs of LC droplets to classify and quantify adsorbed surfactants. In addition, we report computational capabilities to determine relevant optical features extracted by the CNN from LC micrographs, which can provide insights into surfactant adsorption phenomena at LC-water interfaces. Overall, the combination of microcontact-printed LC arrays and machine learning provides a convenient and robust platform that could prove useful for developing high-throughput sensors for on-site testing of environmentally or biologically relevant amphiphiles.

A Self-defense Hierarchical Antibacterial Surface with Inherent Antifouling and Bacteria-activated Bactericidal Properties for Infection Resistance

Biomedical device-associated infection (BAI) is one of the main reasons for the function failure of implants in clinic practices. Development of high-efficiency antibacterial materials is of great significance to reduce...