One step synthesis of gold-loaded radial mesoporous silica nanospheres and supported lipid bilayer functionalization: towards bio-multifunctional sensors

Surfactant stabilized gold nanomaterials for environmental sensing applications - A review

Surfactant stabilized Gold (Au) nanomaterials (NMs) have been documented extensively in recent years for numerous sensing applications in the academic literature. Despite the crucial role these surfactants play in the sensing applications, the comprehensive reviews that highlights the fundamentals associated with these assemblies and impact of these surfactants on the properties and sensing mechanisms are still quite scare. This review is an attempt in organizing the vast literature associated with this domain by providing critical insights into the fundamentals, preparation methodologies and sensing mechanisms of these surfactant stabilized Au NMs. For the simplification, the surfactants are divided into the typical and advanced surfactants and the Au NMs are classified into Au nanoparticles (NPs) and Au nanoclusters (NCs) depending upon the complexity in structure and size of the NMs respectively. The preparative methodologies are also elaborated for enhancing the understanding of the readers regarding such assemblies. The case studies regarding surfactant stabilized Au NMs were further divided into colorimetric sensors, surface plasmonic resonance (SPR) based sensors, luminescence-based sensors, and electrochemical/electrical sensors depending upon the property utilized by the sensor for the sensing of an analyte. Future perspectives are also discussed in detail for the researchers looking for further progress in that particular research domain.

Enhanced efficacy and drug delivery with lipid coated mesoporous silica nanoparticles in cancer therapy

The exposure of cancer cells to subtherapeutic drug concentrations results in multidrug resistance (MDR). The uniqueness of mesoporous silica nanoparticles (MSNPs) with larger surface area for higher drug loading can solve the issue by delivering higher amounts of chemotherapeutics to the cancer cells. However, premature drug release and lower biocompatibility remain challenging. Lipid coating of MSNPs at the same time, can enhance the stability and biocompatibility of nanocarriers. Furthermore, the lipid coating can reduce the systemic drug release and deliver higher amounts to the tumor site. Herein, lipid coated MSNPs were prepared by utilizing cationic liposomes and further investigations were made. Our studies have shown the higher entrapment of doxorubicin (Dox) to MSNPs due to availability of porous structure. Lipid coating could provide a barrier to sustain the release of drug along with reduced premature leakage. In addition, the biocompatibility and enhanced interaction of cationic liposomes to cell membranes resulted in better cellular uptake. Lipid coated silica nanoparticles have shown higher cellular toxicity as compared to non-lipid coated particles. The increase in cytotoxicity with time supports the hypothesis of sustained release of drug from lipid coated MSNPs. We propose the Lip-Dox-MSNPs as an effective approach to treat cancer by delivering and maintaining effective concentration of drugs to the tumor site without systemic side effects.

Highly Thiolated Dendritic Mesoporous Silica Nanoparticles with High-Content Gold as Nanozymes: The Nano-Gold Size Matters

Thiolated dendritic mesoporous silica nanoparticles (T-DMSNs) with ultrahigh density of thiol groups (284.6 ± 9 μmol g^-1) are synthesized and used to load gold nanoparticles with tunable sizes (1.2-2.7 nm) and high content (34.0 wt %). It is demonstrated that the size of gold nanoparticles has a significant impact on their peroxidase-mimicking activity. At an optimized size of 1.9 nm, T-DMSNs@Au exhibits the highest activity. Our contribution provides new insights into the rational design of nanozymes for future applications.

Polyelectrolyte multilayer-cushioned fluid lipid bilayers: a parachute model

Lipid bilayer membranes supported on polyelectrolyte multilayers are widely used as a new biomembrane model that connects biological and artificial materials since these ultrathin polyelectrolyte supports may mimic the role of the extracellular matrix and cell skeleton in living systems. Polyelectrolyte multilayers were fabricated by a layer-by-layer self-assembly technique. A quartz crystal microbalance with dissipation was used in real time to monitor the interaction between phospholipids and polyelectrolytes in situ on a planar substrate. The surface properties of polyelectrolyte films were investigated by the measurement of contact angles and zeta potential. Phospholipid charge, buffer pH and substrate hydrophilicity were proved to be essential for vesicle adsorption, rupture, fusion and formation of continuous lipid bilayers on the polyelectrolyte multilayers. The results clearly demonstrated that only the mixture of phosphatidylcholine and phosphatidic acid (4 : 1) resulted in fluid bilayers on chitosan and alginate multilayers with chitosan as a top layer at pH 6.5. A coarse-grained molecular simulation study elucidated that the exact mechanism of the formation of fluid lipid bilayers resembles a "parachute" model. As the closest model to the real membrane, polyelectrolyte multilayer-cushioned fluid lipid bilayers can be appropriate candidates for application in biomedical fields.

Multianalytical approach for surface- and tip-enhanced infrared spectroscopy study of a molecule–metal conjugate: deducing its adsorption geometry

Multianalytical approach to the surface-enhanced infrared absorption spectroscopy (SEIRA) and tip-enhanced infrared nanospectroscopy (TEIRA) studies of α-methyl-dl-tryptophan adsorption geometry on a gold nanoparticle surface.

Functionalized Mesoporous Silica Nanoparticle with Antioxidants as a New Carrier That Generates Lower Oxidative Stress Impact on Cells

Mesoporous silica nanoparticles (MSNs) were covalently coated with antioxidant molecules, namely, caffeic acid (MSN-CAF) or rutin (MSN-RUT), in order to diminish the impact of oxidative stress induced after transfection into cells, thus generating safer carriers used for either drug delivery or other applications. Two cellular models involved in the entry of NPs in the body were used for this purpose: the intestinal Caco-2 and the epidermal HaCaT cell lines. Rutin gave the best results in terms of antioxidant capacities preservation during coupling procedures, cellular toxicity alleviation, and decrease of ROS level after 24 h incubation of cells with grafted nanoparticles. These protective effects of rutin were found more pronounced in HaCaT than in Caco-2 cells, indicating some cellular specificity toward defense against oxidative stress. In order to gain more insight about the Nrf2 response, a stable transfected HaCaT cell line bearing repeats of the antioxidant response element (ARE) in front of a luciferase reporter gene was generated. In this cell line, both tBHQ and quercetin (Nrf2 agonists), but not rutin, were able to induce, in a dose-dependent fashion, the luciferase response. Interestingly, at high concentration, MSN-RUT was able to induce a strong Nrf2 protective response in HaCaT cells, accompanied by a comparable induction of HO-1 mRNA. The level of these responses was again less important in Caco-2 cells. To conclude, in keratinocyte cell line, the coupling of rutin to silica nanoparticles was beneficial in term of ROS reduction, cellular viability, and protective effects mediated through the activation of the Nrf2 antioxidant pathway.

Synthesis, decoration, and cellular effects of magnetic mesoporous silica nanoparticles

Synthesis of magnetic core@shell nanoparticles with different coatings and the study of their uptake by cells.

Au encapsulated into Al-MCM-41 mesoporous material: in situ synthesis and electronic structure

A facile one-step technique is proposed for the successful synthesis of highly ordered Au/Al-MCM-41. The charge state of Au³⁺ in the mesoporous framework was partially reduced due to the accompanying Al when clay was used as source.