Permanent superhydrophilic surface modification in microporous polydimethylsiloxane sponge for multi-functional applications

Honeycomb-Inspired Surface-Enhanced Raman Scattering Microarray for Large-Area Automated Testing of Urease in Saliva Samples

Surface-enhanced Raman scattering (SERS) technology, as an important analytical tool, has been widely applied in the field of chemical and biomedical sensing. Automated testing is often combined with biochemical analysis technologies to shorten the detection time and minimize human error. The present SERS substrates for sample detection are time-consuming and subject to high human error, which are not conducive to the combination of SERS and automated testing. Here, a novel honeycomb-inspired SERS microarray is designed for large-area automated testing of urease in saliva samples to shorten the detection time and minimize human error. The honeycomb-inspired SERS microarray is decorated with hexagonal microwells and a homogeneous distribution of silver nanostars. Compared with the other four common SERS substrates, the optimal honeycomb-inspired SERS microarray exhibits the best SERS performance. The RSD of 100 SERS spectra continuously collected from saliva samples is 6.56%, and the time of one detection is reduced from 5 min to 10 s. There is a noteworthy linear relationship with a R2 of 0.982 between SERS intensity and urease concentration, indicating the quantitative detection capability of the urease activity in saliva samples. The honeycomb-inspired SERS microarray, combined with automated testing, provides a new way in which SERS technology can be widely used in biomedical applications.

Silicone cryogel skeletons enhance the survival and mechanical integrity of hydrogel-encapsulated cell therapies

The transplantation of engineered cells that secrete therapeutic proteins presents a promising method for addressing a range of chronic diseases. However, hydrogels used to encase and protect non-autologous cells from immune rejection often suffer from poor mechanical properties, insufficient oxygenation, and fibrotic encapsulation. Here, we introduce a composite encapsulation system comprising an oxygen-permeable silicone cryogel skeleton, a hydrogel matrix, and a fibrosis-resistant polymer coating. Cryogel skeletons enhance the fracture toughness of conventional alginate hydrogels by 23-fold and oxygen diffusion by 2.8-fold, effectively mitigating both implant fracture and hypoxia of encapsulated cells. Composite implants containing xenogeneic cells engineered to secrete erythropoietin significantly outperform unsupported alginate implants in therapeutic delivery over 8 weeks in immunocompetent mice. By improving mechanical resiliency and sustaining denser cell populations, silicone cryogel skeletons enable more durable and miniaturized therapeutic implants.

A one-step process for multi-gradient wettability modification on a polymer surface

The surface modification technique is applied in microfluidic devices to modify wettability and achieve different flow velocities. Currently available methods for poly(dimethylsiloxane) (PDMS) surfaces may reliably induce wettability changes, but only one area can be altered at a time. This work introduces the controlled gradient oxygen plasma modification (CGPM) technique, which layers several resin masks with varying porosities on top of the PDMS surface. Selective wettability of the PDMS surface can be achieved by varying the oxygen plasma density above the modified material's surface by manipulation of the porosity value. Through the implementation of the COMSOL plasma module, the impact of the mask's porosity, through-hole size, distribution, and distance from the PDMS surface on wettability was studied. The suggested CGPM approach was characterized by contact angle measurements. During the 25-second CGPM procedure, the PDMS surface's contact angle continually changed from 8.77° to 76.98°. An integrated microfluidic device was created and manufactured to identify D-dimers to illustrate this method. In comparison with standard oxygen plasma treatment, the D-dimer assay was finished in 10 minutes and had a dynamic range of 1-1000 ng mL-1, with a peak fluorescence signal augmentation of 78.3% and an average fluorescence intensity enhancement of 31.1%.

Functional PDMS Elastomers: Bulk Composites, Surface Engineering, and Precision Fabrication

Polydimethylsiloxane (PDMS)-the simplest and most common silicone compound-exemplifies the central characteristics of its class and has attracted tremendous research attention. The development of PDMS-based materials is a vivid reflection of the modern industry. In recent years, PDMS has stood out as the material of choice for various emerging technologies. The rapid improvement in bulk modification strategies and multifunctional surfaces has enabled a whole new generation of PDMS-based materials and devices, facilitating, and even transforming enormous applications, including flexible electronics, superwetting surfaces, soft actuators, wearable and implantable sensors, biomedicals, and autonomous robotics. This paper reviews the latest advances in the field of PDMS-based functional materials, with a focus on the added functionality and their use as programmable materials for smart devices. Recent breakthroughs regarding instant crosslinking and additive manufacturing are featured, and exciting opportunities for future research are highlighted. This review provides a quick entrance to this rapidly evolving field and will help guide the rational design of next-generation soft materials and devices.

Determination of volatile components in cumin by microwave-assisted PDMS/GO/DES headspace solid phase extraction combined with GC-MS

A novel approach based on polydimethylsiloxane/graphene oxide/deep eutectic solvent (PDMS/GO/DES) sponge headspace solid phase extraction followed by GC-MS was successfully developed to determine the volatile components in cumin. The PDMS/GO/DES exhibits outstanding properties with high adsorption capacity and good chemical stability, and has shown its potentiality as an ideal adsorbent for the extraction of volatile compounds. The influence factors of the extraction process were investigated. Excellent analytical performances were achieved, including wide linearity (0.60-107.72 ng) with high correlation coefficients (R² ≥ 0.9951), low LODs (0.23-9.23 ng) and LOQs (0.54-18.47 ng), satisfactory precision (intra-day RSDs ≤ 2.85% and inter-day RSDs ≤ 3.92%). Under the optimal extraction conditions, the volatile components in 17 cumin samples from four origins in Xinjiang were analyzed and 31 compounds were identified. PCA was used to establish the relationship between the origins and the volatile compounds for further discriminant analysis. The results showed that the PDMS/GO/DES method was a rapid, simple and sensitive technique for the analysis of volatile components in spices.

One-step zwitterionization and quaternization of thick PDMAEMA layer grafted through subsurface-initiated ATRP for robust antibiofouling and antibacterial coating on PDMS

In this work, we demonstrate the grafting of thick poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA) layer on PDMS via subsurface-initiated atom transfer radical polymerization (SSI-ATRP). The self-migration of DMAEMA monomers into the subsurface of PDMS is proven to be the dominant factor for the success of SSI-ATRP. The as-prepared thick microscale graft layer on PDMS shows much better abrasion resistance than nanoscale graft layer obtained by conventional surface-initiated atom transfer radical polymerization (SI-ATRP) under identical condition. Taking advantage of the tertiary amines of PDMAEMA, the simultaneous zwitterionization and quaternization of the PDMAEMA thick layer is realized through a facile one-step process. The effect of zwitterionization and quaternization degree on the antibiofouling and antibacterial properties is investigated. The results show that a relatively high zwitterionization degree (75 mol%) and a low quaternization degree (25 mol%) exhibit a good well-balanced effect on both fouling repellence and bactericidal activity. This work may lead to the development of robust bifunctional antibiofouling and antibacterial surfaces via SSI-ATRP strategy.

Separation of distinct exosome subpopulations: isolation and characterization approaches and their associated challenges

Exosomes are nano-sized extracellular vesicles that serve as a communications system between cells and have shown tremendous promise as liquid biopsy biomarkers in diagnostic, prognostic, and even therapeutic use in different human diseases. Due to the natural heterogeneity of exosomes, there is a need to separate exosomes into distinct biophysical and/or biochemical subpopulations to enable full interrogation of exosome biology and function prior to the possibility of clinical translation. Currently, there exists a multitude of different exosome isolation and characterization approaches which can, in limited capacity, separate exosomes based on biophysical and/or biochemical characteristics. While notable reviews in recent years have reviewed these approaches for bulk exosome sorting, we herein present a comprehensive overview of various conventional technologies and modern microfluidic and nanotechnological advancements towards isolation and characterization of exosome subpopulations. The benefits and limitations of these different technologies to improve their use for distinct exosome subpopulations in clinical practices are also discussed. Furthermore, an overview of the most commonly encountered technical and biological challenges for effective separation of exosome subpopulations is presented.

Surface Coating with Hyaluronic Acid-Gelatin-Crosslinked Hydrogel on Gelatin-Conjugated Poly(dimethylsiloxane) for Implantable Medical Device-Induced Fibrosis

Polydimethylsiloxane (PDMS) is a biocompatible polymer that has been applied in many fields. However, the surface hydrophobicity of PDMS can limit successful implementation, and this must be reduced by surface modification to improve biocompatibility. In this study, we modified the PDMS surface with a hydrogel and investigated the effect of this on hydrophilicity, bacterial adhesion, cell viability, immune response, and biocompatibility of PDMS. Hydrogels were created from hyaluronic acid and gelatin using a Schiff-base reaction. The PDMS surface and hydrogel were characterized using nuclear magnetic resonance, X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and scanning electron microscopy. The hydrophilicity of the surface was confirmed via a decrease in the water contact angle. Bacterial anti-adhesion was demonstrated for Pseudomonas aeruginosa, Ralstonia pickettii, and Staphylococcus epidermidis, and viability and improved distribution of human-derived adipose stem cells were also confirmed. Decreased capsular tissue responses were observed in vivo with looser collagen distribution and reduced cytokine expression on the hydrogel-coated surface. Hydrogel coating on treated PDMS is a promising method to improve the surface hydrophilicity and biocompatibility for surface modification of biomedical applications.

Polydimethylsiloxane/ionic liquid sponge used in headspace solid-phase extraction coupled with GC-MS for rapid analysis of essential oil in lavender

A headspace (HS) solid-phase extraction (SPE) based on polydimethylsiloxane (PDMS)/ionic liquid (IL) sponge was developed for the extraction of lavender essential oil. The PDMS after loading of 1-butyl-3-methylimidazolium tetrachloroferrate ([BMIM]FeCl₄ ) with a high surface area and excellent adsorption capacity was successfully applied in the SPE process. Microwave distillation (MD) coupled with HS-PDMS/[BMIM]FeCl₄ extraction after GC-MS was proposed. Various experimental parameters were studied. The optimal conditions were as follows: optimal IL, [BMIM]FeCl₄ ; volume ratio of IL to ethanol, 1:5; extraction solvent, n-hexane; microwave power, 600 W; and irradiation time, 12 min. The limits of detection and quantification of the analytic compounds were in the ranges 4.00-16.32 and 10.00-40.00 ng, respectively. The intra-day and inter-day precisions were in the ranges 0.37-1.94% and 1.20-2.45%, respectively. Under the optimized conditions, 13 samples of 3 lavender varieties were analyzed, and 40 compounds were identified. Lavender varieties were distinguished using principal component analysis. The results showed that MD-HS-PDMS/IL-GC-MS is a novel, simple, and sensitive method for the determination of essential oil in complex plant samples.