SERS Assays Based on Electrospun Nanofibers: Preparation and Analytical Applications

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool and an up-to-date method of analytical chemistry due to its high sensitivity and fingerprint recognition capabilities. Nowadays SERS due to its label-free detection capabilities is being actively developed in medical fields, for example in the analysis of biologically important substances in different matrixes, for potential on-site detection of toxic substances, food safety, and so on. To get the SERS signal, it is necessary the presence of plasmonic nanostructures in the SERS substrates. Electrospun nanofibers have been an attractive alternative to SERS-platforms due to the diversity of advantages, including ease of preparation, structure flexibility, and others. In this review, we summarized the methods of plasmonic nanostructures incorporating substrate based on electrospun nanofibers. Also, the analytical application of SERS-active electrospun nanofibers with embedded nanostructures focused on biologically significant molecules is observed in detail. Finally, the future outlook in the application of these substrates in bioanalysis as the most promising area in analytical chemistry is presented.

CaCO3-based carriers with prolonged release property for antifungal drug delivery to hair follicles

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...

Recrystallization of CsPbBr3 Nanoparticles in Fluoropolymer Nonwoven Mats for Down- and Up-Conversion of Light

Inorganic halides perovskite CsPbX₃ (X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) nanoparticles are efficient light-conversion objects that have attracted significant attention due to their broadband tunability over the entire visible spectral range of 410–700 nm and high quantum yield of up to 95%. Here, we demonstrate a new method of recrystallization of CsPbBr₃ nanoparticles inside the electrospun fluoropolymer fibers. We have synthesized nonwoven tetrafluoroethylene mats embedding CsPbBr₃ nanoparticles using inexpensive commercial precursors and syringe electrospinning equipment. The fabricated nonwoven mat samples demonstrated both down-conversion of UV light to 506 nm and up-conversion of IR femtosecond laser radiation to 513 nm green photoluminescence characterized by narrow emission line-widths of 35 nm. Nanoparticle formation inside nonwoven fibers was confirmed by TEM imaging and water stability tests controlled by fluorimetry measurements. The combination of enhanced optical properties of CsPbBr₃ nanoparticles and mechanical stability and environmental robustness of highly deformable nonwoven fluoropolymer mats is appealing for flexible optoelectronic applications, while the industry-friendly fabrication method is attractive for commercial implementations.

Biodegradable Microcapsules Loaded with Nerve Growth Factor Enable Neurite Guidance and Synapse Formation

Neurological disorders and traumas often involve loss of specific neuronal connections, which would require intervention with high spatial precision. We have previously demonstrated the biocompatibility and therapeutic potential of the layer-by-layer (LbL)-fabricated microcapsules aimed at the localized delivery of specific channel blockers to peripheral nerves. Here, we explore the potential of LbL-microcapsules to enable site-specific, directional action of neurotrophins to stimulate neuronal morphogenesis and synaptic circuit formation. We find that nanoengineered biodegradable microcapsules loaded with nerve growth factor (NGF) can guide the morphological development of hippocampal neurons in vitro. The presence of NGF-loaded microcapsules or their clusters increases the neurite outgrowth rate while boosting neurite branching. Microcapsule clusters appear to guide the trajectory of developing individual axons leading to the formation of functional synapses. Our observations highlight the potential of NGF-loaded, biodegradable LbL-microcapsules to help guide axonal development and possibly circuit regeneration in neuropathology.

Alpha-2-macroglobulin loaded microcapsules enhance human leukocyte functions and innate immune response

Synthetic microstructures can be engineered to deliver bioactive compounds impacting on their pharmacokinetics and pharmacodynamics. Herein, we applied dextran-based layer-by-layer (LbL) microcapsules to deliver alpha-2-macroglobulin (α2MG), a protein with modulatory properties in inflammation. Extending recent observations made with dextran-microcapsules loaded with α2MG in experimental sepsis, we focused on the physical and chemical characteristics of these microstructures and determined their biology on rodent and human cells. We report an efficient encapsulation of α2MG into microcapsules, which enhanced i) human leukocyte recruitment to inflamed endothelium and ii) human macrophage phagocytosis: in both settings microcapsules were more effective than soluble α2MG or empty microcapsules (devoid of active protein). Translation of these findings revealed that intravenous administration of α2MG-microcapsules (but not empty microcapsules) promoted neutrophil migration into peritoneal exudates and augmented macrophage phagocytic functions, the latter response being associated with alteration of bioactive lipid mediators as assessed by mass spectrometry. The present study indicates that microencapsulation can be an effective strategy to harness the complex biology of α2MG with enhancing outcomes on fundamental processes of the innate immune response paving the way to potential future development in the control of sepsis.

Multilayer Capsules of Bovine Serum Albumin and Tannic Acid for Controlled Release by Enzymatic Degradation

With the purpose to replace expensive and significantly cytotoxic positively charged polypeptides in biodegradable capsules formed via Layer-by-Layer (LbL) assembly, multilayers of bovine serum albumin (BSA) and tannic acid (TA) are obtained and employed for encapsulation and release of model drugs with different solubility in water: hydrophilic-tetramethylrhodamine-isothiocyanate-labeled BSA (TRITC-BSA) and hydrophobic 3,4,9,10-tetra-(hectoxy-carbonyl)-perylene (THCP). Hydrogen bonding is proposed to be predominant within thus formed BSA/TA films. The TRITC-BSA-loaded capsules comprising 6 bilayers of the protein and polyphenol are benchmarked against the shells composed of dextran sulfate (DS) and poly-l-arginine (PARG) on degradability by two proteolytic enzymes with different cleavage site specificity (i.e., α-chymotrypsin and trypsin) and toxicity for murine RAW264.7 macrophage cells. Capsules of both types possess low cytotoxicity taken at concentrations equal or below 50 capsules per cell, and evident susceptibility to α-chymotrypsin resulted in release of TRITC-BSA. While the BSA/TA-based capsules clearly display resistance to treatment with trypsin, the assemblies of DS/PARG extensively degrade. Successful encapsulation of THCP in the TRITC-BSA/TA/BSA multilayer is confirmed, and the release of the model drug is observed in response to treatment with α-chymotrypsin. The thickness, surface morphology, and enzyme-catalyzed degradation process of the BSA/TA-based films are investigated on a planar multilayer comprising 40 bilayers of the protein and polyphenol deposited on a silicon wafer. The developed BSA/TA-based capsules with a protease-specific degradation mechanism are proposed to find applications in personal care, pharmacology, and the development of drug delivery systems including those intravenous injectable and having site-specific release capability.

Improved and targeted delivery of bioactive molecules to cells with magnetic layer-by-layer assembled microcapsules

Despite our increasing knowledge of cell biology and the recognition of an increasing repertoire of druggable intracellular therapeutic targets, there remain a limited number of approaches to deliver bioactive molecules to cells and even fewer that enable targeted delivery. Layer-by-layer (LbL) microcapsules are assembled using alternate layers of oppositely charged molecules and are potential cell delivery vehicles for applications in nanomedicine. There are a wide variety of charged molecules that can be included in the microcapsule structure including metal nanoparticles that introduce physical attributes. Delivery of bioactive molecules to cells with LbL microcapsules has recently been demonstrated, so in this study we explore the delivery of bioactive molecules (luciferase enzyme and plasmid DNA) to cells using biodegradable microcapsules containing a layer of magnetite nanoparticles. Interestingly, significantly improved intracellular luciferase enzyme activity (25 fold) and increased transfection efficiency with plasmid DNA (3.4 fold) was observed with magnetic microcapsules. The use of a neodymium magnet enabled efficient targeting of magnetic microcapsules which further improved the delivery efficiency of the cargoes as a consequence of increased microcapsule concentration at the magnetic site. Microcapsules were well tolerated by cells in these experiments and only displayed signs of toxicity at a capsule : cell ratio of 100 : 1 and with extended exposure. These studies illustrate how multi-functionalization of LbL microcapsules can improve and target delivery of bioactive molecules to cells.

Magnetically engineered microcapsules as intracellular anchors for remote control over cellular mobility

Living cells are anchored with magnetic microcapsules that allow in vitro manipulation via a magnetic field.

Microparticle alpha-2-macroglobulin enhances pro-resolving responses and promotes survival in sepsis

Incorporation of locally produced signaling molecules into cell-derived vesicles may serve as an endogenous mediator delivery system. We recently reported that levels alpha-2-macroglobulin (A2MG)-containing microparticles are elevated in plasma from patients with sepsis. Herein, we investigated the immunomodulatory actions of A2MG containing microparticles during sepsis. Administration of A2MG-enriched (A2MG-E)-microparticles to mice with microbial sepsis protected against hypothermia, reduced bacterial titers, elevated immunoresolvent lipid mediator levels in inflammatory exudates and reduced systemic inflammation. A2MG-E microparticles also enhanced survival in murine sepsis, an action lost in mice transfected with siRNA for LRP1, a putative A2MG receptor. In vitro, A2MG was functionally transferred onto endothelial cell plasma membranes from microparticles, augmenting neutrophil–endothelial adhesion. A2MG also modulated human leukocyte responses: enhanced bacterial phagocytosis, reactive oxygen species production, cathelicidin release, prevented endotoxin induced CXCR2 downregulation and preserved neutrophil chemotaxis in the presence of LPS. A significant association was also found between elevated plasma levels of A2MG-containing microparticles and survival in human sepsis patients. Taken together, these results identify A2MG enrichment in microparticles as an important host protective mechanism in sepsis.

Lessons in microcapsule assembly from imaging delivery of a bioluminescent enzyme

Layer-by-layer assembled microcapsules have potential applications as delivery and biosensing systems, which make them attractive tools for use in various aspects of nanomedicine. We examined the effect of microcapsule location on activity of the bioluminescent enzyme luciferase in both intact capsules and following cell uptake. In intact capsules, the rate of reaction of luciferase was greatest for luciferase in the outer layer and least in the core. Following cell uptake, luciferase in the outer layer was rapidly reactive, and a similar rate of reaction and activity was observed for luciferase placed in capsule interior (core). By contrast, there was minimal activity detected when microcapsules with luciferase sandwiched between polyelectrolytes in a middle layer were delivered to cells. This study informs us of the availability of bioactive molecules located in different positions within microcapsules and will enable better microcapsule construction in line with the intended application, particularly delivery of functional proteins to cells.