The use of surface enhanced Raman spectroscopy (SERS) is limited by low reproducibility and uniformity of the response. Solving these problems can turn the laboratory use of SERS into real-world application. In this regard, soft SERS-active substrates can enable portable instrumentation and reduce costs in the fabrication of SERS-based sensors. Here, plasmonic free-standing films made of biocompatible chitosan nanofibers and gold nanoparticles are engineered by a simple protocol varying the concentration of chloroauric acid. The concentration and distribution of gold nanoparticles in films are controlled in a predictable way, and SERS spectra for the standard 2-naphthalenethiol with concentration less than 10(-15) M are acquired in a reproducible way. The statistical analysis reveals a relatively high and locally uniform performance of SERS with an enhancement factor of 2 × 10(5) for 86% of the points on the imaged area of the SERS substrate. Potential SERS detection of small molecules, both Rhodamine 6G and d-Glucose, in the micromolar range is demonstrated.

Superficial fungal infections are of serious concern worldwide due to their morbidity and increasing distribution across the globe in this era of growing antimicrobial resistance. Delivery of antifungals to target...

Biomaterials engineered with specific cell binding sites, tunable mechanical properties, and complex architectures are essential to control cell adhesion and proliferation. The influence of the local properties, such as the local hardness and stability on the interaction with cells, has not been yet fully understood and exploited. This is particularly relevant for hydrogels, very promising materials with, unfortunately, poor cell adhesion properties, attributed mostly to their softness. Here, we propose a new approach for producing hybrid hydrogels by functionalizing them with particles and performing a thermal treatment. Exploring the interaction of cells with these materials we introduce a new concept, cells-grabbing-onto-particles, a facilitation of the cell adhesion through modulation of local properties. The approach is implemented on alginate hydrogels typically unsuitable for cell growth by turning them into a very effective cell culture growth platform. Specifically, alginate hydrogels are bio-mineralized with calcium carbonate (CaCO3) particles, where an additional thermal annealing (T-A) process has been applied. The local Young’s modulus of new T-A treated hybrid hydrogels has increased to over 3 MPa on areas of hydrogels containing particles and to around 1 MPa on areas without particles, which is drastically different from 130 to 180 kPa values for unmodified hydrogels. Intriguingly, our results show that enhancement of local mechanical properties alone is a necessary, but insufficient, condition; the particles must be stably fixed in gels for cell growth and proliferation. Extended for hydrogels functionalized with silica particles too, the cells-grab-on-particles concept is shown applicable to different materials and cells for cell biology and tissue engineering.

Microbubbles have already reached clinical practice as ultrasound contrast agents for angiography. However, modification of the bubbles’ shell is needed to produce probes for ultrasound and multimodal (fluorescence/photoacoustic) imaging methods in combination with theranostics (diagnostics and therapeutics). In the present work, hybrid structures based on microbubbles with an air core and a shell composed of bovine serum albumin, albumin-coated gold nanoparticles, and clinically available photodynamic dyes (zinc phthalocyanine, indocyanine green) were shown to achieve multimodal imaging for potential applications in photodynamic therapy. Microbubbles with an average size of 1.5 ± 0.3 μm and concentration up to 1.2 × 109 microbubbles/mL were obtained and characterized. The introduction of the dye into the system reduced the solution’s surface tension, leading to an increase in the concentration and stability of bubbles. The combination of gold nanoparticles and photodynamic dyes’ influence on the fluorescent signal and probes’ stability is described. The potential use of the obtained probes in biomedical applications was evaluated using fluorescence tomography, raster-scanning optoacoustic microscopy and ultrasound response measurements using a medical ultrasound device at the frequency of 33 MHz. The results demonstrate the impact of microbubbles’ stabilization using gold nanoparticle/photodynamic dye hybrid structures to achieve probe applications in theranostics.