George Warren Greene

Surface-enhanced Raman scattering (SERS) is attractive for molecular diagnostics, but direct sensing in unprocessed whole blood is hindered by biofouling and poor operational stability. Here, we report a biomimetic-SERS platform integrating vancomycin-responsive structure-switching aptamers and a self-assembled lubricin (PRG-4) antifouling layer on a nanostructured plasmonic nanoslide. The aptamer provides molecular recognition, while the hydrated glycocalyx-mimicking lubricin layer suppresses nonspecific adsorption from blood and preserves access of vancomycin to the sensing interface. The sensor enables direct vancomycin detection in unprocessed whole blood with subnanomolar sensitivity and retains analytical performance after 3 weeks of storage. It also shows proof-of-concept operational stability, retaining 75% peak intensity across six measurement cycles over more than 5 weeks. Although repeated 20 min UV-Ozone cleaning reduces calibration sensitivity, the nanoslide maintains qualitative detection capability and SERS activity, supporting its potential for point-of-use therapeutic drug monitoring.

Rapid glycophenotyping is often limited by biofouling, reliance on complex, multistep labeling, and poor access to living cell surfaces. Here, however, we introduce a glycocalyx-mimetic electrochemical interface that converts lectin-glycan binding into multiplex electrical signals. We coat gold electrodes with a self-assembled brush of lubricin (PRG4), whose densely O-glycosylated mucin domains present tumor-associated truncated O-glycans that serve as linkers to the lectins, our recognition elements. Embedding six lectins within lubricin enables orthogonal recognition of Gal-GalNAc-terminated oligosaccharides. In an electrochemical culture-plate format, the resulting sensor supports real-time, in situ glycophenotyping of melanoma cells, achieving quantitative agreement to a conventional, end point, lectin microarray. This glycocalyx-mimetic transducer thus enables the rapid, label-free screening of lectin-glycan interactions and the profiling of diagnostically relevant, tumor-associated glycans.

Electrochemical aptamer-based (EAB) sensors promise real-time, reagent-free drug and biomarker monitoring, but protein adsorption and enzymatic degradation of their target-recognizing aptamers rapidly depress their signal and induce drift in complex matrices, such as saliva or undiluted whole blood. Size-excluding hydrogels offer an approach to reducing these effects, but the problem remains of achieving long-duration operation without significantly throttling the analyte transport or electron transfer to the electrode. In response, here we show that a tetra-poly(ethylene glycol) (tetra-PEG) hydrogel coating forms a soft, highly hydrated, ∼31 nm mesh network that excludes large glycoproteins and cellular components, reduces drift while preserving electron transfer, and enables acceptably rapid small-molecule access. Specifically, in undiluted saliva and bovine blood, this coating reduces electrode fouling and helps sustain EAB performance. For example, in undiluted whole blood at 37 °C, hydrogel-protected sensors exhibit lower drift over 8 h (∼5.7 vs ∼25.1% for unprotected controls) while maintaining a comparable signal gain across the tested vancomycin concentrations. It thus appears that the tetra-PEG hydrogel network can balance antifouling efficacy and nuclease resistance with electron transfer compatibility, suggesting that it may prove to be a practical route to long-duration, in-matrix, and, ultimately, in vivo monitoring using EAB sensors.

Rapid, real-time, and ultrasensitive molecular sensing in unprocessed whole blood remains a major challenge due to biofouling, narrow dynamic ranges, and the need for rapid equilibration. We report a biomimetic surface-enhanced Raman scattering (SERS) platform that integrates structure-switching aptamers with a self-assembling, lubricin (proteoglycan 4; PRG4)-derived glycocalyx mimicking structure that enables ultrasensitive, real-time detection directly within unprocessed whole bovine blood. This architecture achieves femtomolar detection in buffer and sub-nanomolar quantification in whole blood, expanding the dynamic range by six orders of magnitude compared to electrochemical aptamer sensors, while preserving the fast response required for continuous monitoring. In this biomimetic sensor platform, the glycocalyx-like lubricin layer performs multiple functions. (i) It prevents surface biofouling and associated signal losses, instabilities, and interferences. (ii) Lubricin enhances sensor selectivity through size-dependent molecular transport, and (iii) it facilitates amplification via molecular crowding within the lubricin layer, which acts as a signal amplifying mechanism via its effect on aptamer structure-switching dynamics and aptamer-analyte interactions. These findings establish biomimetic-SERS as a generalizable strategy for amplification-free, real-time molecular sensing in complex biofluids, with broad implications for therapeutic drug monitoring and point-of-care diagnostics.

The grafted dopant layer templates nanomorphology and mechanical stiffness of 2D conducting polymer films. Known as tethered dopant templating, the approach enables precise control over physical properties without loss of electrochemical performance.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) pose one of the world's most prominent chemical health threats and are detected in virtually everything from the Antarctic environment to human blood. Due to the extreme half-lives and omnipresent distribution of the chemical class, the threat cannot be eliminated but rather must be continuously monitored and managed through widespread sample testing and targeted remediation long term. Unfortunately, the current standard detection method, liquid chromatography/tandem mass spectrometry (LC/MS/MS), is expensive, time-consuming, and limited to use by highly trained professionals in centralized laboratories. For this reason, there is an urgent need for a field-deployable, affordable, and easy-to-use device for PFAS detection. This paper addresses the issue with a protein-based electrochemical sensor for the point-of-need detection of perfluorooctanoic acid (PFOA), which is one commonly regulated PFAS compound of particular concern. Using two proteins, lubricin (LUB, proteoglycan 4) and human liver fatty acid binding protein engineered with a methylene blue redox tag (FABP1-MB), a response to PFOA is detected at 0.41 ng/L and 0.41 μg/L concentrations. Detection of PFOA is also demonstrated in real water and whole blood samples, demonstrating the sensors' possible future application for both environmental and biomedical monitoring.

Drug delivery platforms are frequently susceptible to nonspecific adsorption of biological materials upon contact with biological fluids that can interfere with the controlled release of drugs, affecting both the rate and amount of drug released. To improve the controlled release efficiency of drugs within biological environments, lubricin (also known as PRG4) antifouling coatings were applied to control the release of poly(3,4-ethylenedioxythiophene) (PEDOT) films doped with the model drug phenol red. Drug release experiments comparing uncoated and lubricin-coated PEDOT were performed in nonfouling PBS buffer to assess the impact of lubricin coating on the release of drug from the films, while identical experiments were performed in concentrated solutions of highly fouling proteins to investigate lubricin's capacity to mitigate the effects of surface biofouling on the drug release properties. These experiments revealed that lubricin coating did not create a physical or diffusional barrier to the release of phenol red from PEDOT under nonfouling conditions. Likewise, within a highly fouling protein solution, the lubricin-coated PEDOT films showed greatly enhanced phenol red release compared with uncoated films under passive conditions and active release under an applied negative potential. This greater phenol red release from the lubricin-coated PEDOT was attributed to lubricin's capacity to protect the surface from fouling by nonspecifically adsorbed proteins, which impede the release of phenol red. This study demonstrated that lubricin can effectively improve drug release from PEDOT films in highly fouling environments, resulting in more accurate and reliable dosing.

The development of 2D materials is rapidly advancing beyond traditional graphene and metal oxides and into new functional organic materials including conducting polymers (CPs). Synthesizing 2D-CPs, typically achieved by polymerizing within a highly confined space (e.g., between lipid bilayers), is a slow and poorly scalable process that is incapable of producing large area films. A ‘tethered-dopant templating’ method is used where a surface-grafted layer of dopant molecules regulates the 3D-growth of poly 3,4-ethylenedioxythiophene (PEDOT) allowing ultrathin and molecular-scale ′2D′ films having thicknesses of just ∼3 nm to be grown in an unconfined geometry over a large area (i.e., cm2). While the tethered-dopant template method is a simple and promising alternative to confined geometry templating, the electrochemical mechanisms of film growth and its impact on the film electrochemical properties have yet to be well understood. This investigation shows that the surface-tethered dopant regulates the polymerization reaction by actively suppressing chain termination to support the growth of longer and more conductive chains (i.e., higher charge carrier mobility). These 2D PEDOT films also become ′hyper-doped′ with dopant to polymer mass fractions as high as 8:1, resulting in metal-like conductivity due to enhanced charge carrier density. Additionally, 2D PEDOT films achieve unprecedented homogeneity with little variability down to submicrometer length scales. This new understanding into the dopant regulation over electropolymerization combined with the unequaled metal-like conductivity, molecular-scale dimensions, and large area of 2D PEDOT represents a significant advance in CP materials that will drive innovation across numerous fields including transparent conductors, optoelectronics, bionics, and biosensing.

Organic ionic plastic crystals (OIPCs) are attractive solid electrolyte materials for advanced energy storage systems owing to their inherent advantages (e.g., high plasticity, thermal stability, and moderate ionic conductivity), which can be further improved/deteriorated by the addition of polymer or metal oxide nanoparticles. The role of the nanoparticle/OIPC combinations on the resultant interphase structure and transport properties, however, is still unclear due to the complexity within the composite structures. Herein, we demonstrate a systematic approach to specifically interrogating the interphase region by fabricating layered OIPC/polymer thin films via spin coating and correlating variation in the ionic conductivity of the OIPC with their microscopic structures. In-plane interdigitated electrodes have been employed to obtain electrochemical impedance spectroscopy (EIS) spectra on both OIPC and layered OIPC/polymer thin films. The thin-film EIS measurements were evaluated with conventional bulk EIS measurements on the OIPC pressed pellets and compared with EIS obtained from the OIPC-polymer composites. Interactions between the OIPC and polymer films as well as the morphology of the film surfaces have been characterized through multiple microscopic analysis tools, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and optical profilometry. The combination of EIS analysis with the microscopic visualization of these unique layered OIPC/polymer thin films has confirmed the impact of the OIPC-polymer interphase region on the overall ionic conductivity of bulk OIPC-polymer composites. By changing the chemistry of the polymer substrate (i.e., PMMA, PVDF, and PVDF-HFP), the importance of compatibility between the components in the interphase region is clearly observed. The methods developed here can be used to screen and further understand the interactions among composite components for enhanced compatibility and conductivity.

Surface-enhanced Raman Spectroscopy (SERS) is a powerful optical sensing technique that amplifies the signal generated by Raman scattering by many orders of magnitude. Although the extreme sensitivity of SERS enables an extremely low limit of detection, even down to single molecule levels, it is also a primary limitation of the technique due to its tendency to equally amplify ‘noise’ generated by non-specifically adsorbed molecules at (or near) SERS-active interfaces. Eliminating interference noise is thus critically important to SERS biosensing and typically involves onerous extraction/purification/washing procedures and/or heavy dilution of biofluid samples. Consequently, direct analysis within biofluid samples or in vivo environments is practically impossible. In this study, an anti-fouling coating of recombinant human Lubricin (LUB) was self-assembled onto AuNP-modified glass slides via a simple drop-casting method. A series of Raman spectra were collected using rhodamine 6G (R6G) as a model analyte, which was spiked into NaCl solution or unprocessed whole blood. Likewise, we demonstrate the same sensing system for the quantitative detection of L-cysteine spiked in undiluted milk. It was demonstrated for the first time that LUB coating can mitigate the deleterious effect of fouling in a SERS sensor without compromising the detection of a target analyte, even in a highly fouling, complex medium like whole blood or milk. This feat is achieved through a molecular sieving property of LUB that separates small analytes from large fouling species directly at the sensing interface resulting in SERS spectra with low background (i.e., noise) levels and excellent analyte spectral fidelity. These findings indicate the great potential for using LUB coatings together with an analyte-selective layer to form a hierarchical separation system for SERS sensing of relevant analytes directly in complex biological media, aquaculture, food matrix or environmental samples.