Influence of Defect Engineering in Nanocrystalline CeO2 for Therapeutics of Reactive Oxygen Species-mediated Disorders.

Intracellular oxidative stress generation is a root cause of the dysfunctioning of mitochondria that is accountable for neurodegenerative disorders. In nano-CeO2, the intrinsic redox cycle (Ce3+ ⇔ Ce4+) confers them with a distinct oxygen buffering ability. Thus, increasing the Ce3+/Ce4+ ratio by preferentially engineering oxygen vacancies is expected to boost the antioxidant characteristics in CeO2 nanocrystals (NCs) and hold promise in nanotherapeutics of neurodegenerative disorders. Here, a pristine, economic, and scalable synthesis route with rapid nucleation-growth to yield monodispersed CeO2 NCs of 4 nm has been employed. The NCs demonstrated sustained colloidal stability (zeta potential ~ -30.3±7.2 mV). The survival rate (~96.1% for 0.1 mg/mL) of healthy L929 cells and cell apoptosis induced on the SH-SY5Y cells (~ 30.2% for 0.1 mg/mL) indicate nano-CeO2s' prospects in nanomedicine. The formulated sustainable synthesis strategy for the enrichment of defects in these NCs is anticipated to pave the way for nanocrystal-based-treatments in smart healthcare.Clinical Relevance-This investigation signifies the oxygen vacancy-dependent therapeutic efficacy of CeO2 NCs by ensuring ~96.1% survival rate of L929 cells while demonstrating cell apoptosis on SH-SY5Y cells (~ 30.2%) to establish newer insights on treatment of neurodegenerative disorders.

Continuous flow scale-up of biofunctionalized defective ZnO quantum dots: A safer inorganic ingredient for skin UV protection.

The versatility of ZnO quantum dots (QDs) exhibiting size-tunable visible photoluminescence has propelled them to the forefront of leading-edge innovations in healthcare. At the nano-bio interface, enhancing the singly-ionized oxygen vacancy defects (VO•) through holistic, sustainable synthesis protocols driven by the synergistic influence of QDs' nucleation-growth kinetics has implications on their bioactivity, physiochemical, and optical performance. Recently, robust continuous flow platforms have transcended the conventional batch reactors by alleviating the concerns of "hot-spot" formation due to inhomogeneous heat distribution, acute energy consumption, poor quality, and yield. However, complexities exist in translating batch chemistries into flow processes. Here, a unique, rationally designed continuous flow synthesis of luminescent defect-engineered ZnO QDs (E-QDs) via helical-reactor assembly that can adequately synthesize on a large scale is reported. The crux of this lies in the amalgamation of "green chemistry" and flow synthesis, which results in Lamer-mechanism mediated monodispersed E-QDs demonstrating high photoluminescence quantum yield (PLQY) of 89% under an accurately regulated synthesis environment. Process intensification corroborated that the bio-stable E-QDs manifested admirable photostability, broad-spectrum UV-shielding (400-250 nm), colloidal stability, in vitro biocompatibility against L929 and HaCaT cells, and antioxidant activity. These attributes were better compared to the commercial ZnO nanoparticles (ZnOC-NPs) used for skin UV protection. Delving deeper, the main drivers for the high density of intrinsic VO• formation (Iv/Io∼42.5) were revealed to be the reactor's hydrodynamic performance and the improvised heating rate (2.5°C/sec). Hence, these E-QDs have potential as a new, safe, and economical multifunctional active ingredient for skin UV protection and antioxidants for treating ROS-mediated disorders. STATEMENT OF SIGNIFICANCE: UV filters exhibiting questionable UV-attenuation efficacy and phototoxicity are significant impediments to the healthcare industry emphasizing skin cancer prevention. Although least explored, VO•-governed aberrant photoactive, biological, and surface-reactive qualities of engineered ZnO QDs (E-QDs) have created ample room to investigate these hallmarks for skin UV protection. However, the bottlenecks in stereotypical ZnO QDs production confined by inefficient process control are annihilated by continuous flow strategies. Herein, the high-throughput continuous flow helical reactor assembly was designed and fabricated to successfully showcase optimized transport properties, reproducibility, yield, and quality E-QDs. Anticipating a skyrocketing demand for E-QDs as bioactive-sunscreen components, the comprehensive investigation has demonstrated unprecedented biofunctionality and ROS-scavenging behaviour, even upon UVR exposure, contrary to the traditional nanoparticulate ZnO UV filters.

Multifunctional Photostable Nanocomplex of ZnO Quantum Dots and Avobenzone via the Promotion of Enolate Tautomer.

Ideal multifunctional ultraviolet radiation (UVR) absorbents with excellent photostability, high molar absorptivity, broadband UVR screening, and desired skin sensorial properties remain a significant challenge for the sunscreen industry. The potential of the nanocomplex (NCx) formed by microwave synthesis of ZnO quantum dots (QDs) in the presence of Avobenzone (Av) for achieving these goals is reported. The NCx exhibits unique synergy between ZnO QD and Av components, which enhances the photostability and molar absorptivity, extends UVA filtering range, and provides a visible emission that matches the typical human in vivo skin emission color. Density functional theory (DFT) and time-dependent DFT calculations of ZnO-Av hybrid structures and comparison of their spectroscopic features with experiments suggest that ZnO QDs catalyze the formation of highly photostable surface enolate species via aldol condensation reaction. The combination of experiments and computations used in this study can advance the science and technology of photoprotection.

Surface defect rich ZnO quantum dots as antioxidants inhibiting α-amylase and α-glucosidase: a potential anti-diabetic nanomedicine.

Preventing chronic hyperglycaemia and associated oxidative stress is utmost important for the treatment and management of Type 2 Diabetes Mellitus (T2DM). Here we report the role of different size surface defect rich ZnO quantum dots (D-QDs) for inhibiting metabolic enzymes and scavenging free radicals, which plays a key role in reducing hyperglycaemia and oxidative stress. Quantitative analysis of radical scavenging and metabolic enzyme inhibition activity of D-QDs demonstrates a size dependent behaviour, where D-QDs with a smaller diameter shows superior activity compared to larger size D-QDs. Considering the size dependence in surface defect formation, the increased surface defect density in smaller size D-QDs can be considered as the reason behind this enhancement. Detailed studies establishing the underlying mechanism behind potent free radical scavenging and enzyme inhibition provides an intense scientific rationale for considering D-QDs to design safe and effective nanomedicine for T2DM.

SERS active Ag encapsulated Fe@SiO2 nanorods in electromagnetic wave absorption and crystal violet detection.

The present work is focused on the preparation of Fe nanorods by the chemical reduction of FeCl3 (aq) using NaBH4 in the presence of glycerol as template followed by annealing of the product at 500°C in the presence of H2 gas flow. Subsequently, its surface has been modified by silica followed by silver nanoparticles to form silica coated Fe (Fe@SiO2) and Ag encapsulated Fe@SiO2 nanostructure employing the Stöber method and silver mirror reaction respectively. XRD pattern of the products confirmed the formation of bcc phase of iron and fcc phase of silver, though silica remained amorphous. FESEM images established the growth of iron nanorods from the annealed product and also formation of silica and silver coating on its surface. The appearance of the characteristics bands in FTIR confirmed the presence of SiO2 on the Fe surface. Magnetic measurements at room temperature indicated the ferromagnetic behavior of as prepared iron nanorods, Fe@SiO2 and silver encapsulated Fe@SiO2 nanostructures. All the samples exhibited strong microwave absorption property in the high frequency range (10GHz), though it is superior for Ag encapsulated Fe@SiO2 (-14.7dB) compared with Fe@SiO2 (-9.7dB) nanostructures of the same thickness. The synthesized Ag encapsulated Fe@SiO2 nanostructure also exhibited the SERS phenomena, which is useful in the detection of the carcinogenic dye crystal violet (CV) upto the concentration of 10(-10)M. All these findings clearly demonstrate that the Ag encapsulated Fe@SiO2 nanostructure could efficiently be used in the environmental remediation.

Melt mixed composites of poly(ethylene-co-methacrylic acid) ionomers and multiwall carbon nanotubes: influence of specific interactions.

Multiwall carbon nanotubes (MWNT) were melt-mixed with poly(ethylene-co-methacrylic acid) ionomers (Surlyn) using twin screw microcompounder. The specific interactions existing between the Na+ moieties in Surlyn and the pi electron clouds of MWNT were supported by FTIR and Raman spectroscopic analysis. SAXS scattering patterns were found to be progressively broadened in presence of MWNT in Surlyn/MWNT composites. Morphological investigations revealed selective clustering of MWNT in the vicinity of the ionic domains in Surlyn. Further, the domain size of the ionic clusters was found to increase with increasing MWNT content disrupting the ionic pairs apart in the ionic domain. The melt rheological response of Surlyn was significantly affected in presence of MWNT and was profoundly dependent on the ionic clusters. The state of dispersion of MWNT was assessed by AC electrical conductivity measurements. The associated percolation threshold was observed between 1.5-2 wt% of MWNT.

Specific interactions induced dispersion and confinement of multi-walled carbon nanotubes in co-continuous polymer blends.

Multiwall carbon nanotubes (MWNT) were melt-mixed with 50/50 co-continuous blends of polyamide 6 (PA6) and acrylonitrile-butadiene-styrene (ABS). Blending sequence and moulding processes were found to have a strong impact on the conductivity of the blends with MWNT. Aggregated nature of the tubes, migration during processing and skin-core morphology generated during mould cooling step were found to be crucial parameters affecting the electrical conductivity of the blends. We report here the role of a reactive modifier: sodium salt of 6-amino hexanoic acid (Na-AHA) aiding in uniform dispersion of the MWNT in the 50/50 PA6/ABS blends and restricting the tubes utilizing specific interactions during melt-mixing in the PA6 phase in the blends. We further varied the MWNT to Na-AHA ratio from 1:1 to 1:15 to optimize the concentration of MWNT required in achieving lower electrical percolation threshold in co-continuous PA6/ABS blends. The associated percolation threshold was observed at approximately 0.5 wt% MWNT with high dielectric constant.

Tuning the dispersion of multiwall carbon nanotubes in co-continuous polymer blends: a generic approach.

Melt-mixed blends of polyamide 6 and acrylonitrile-butadiene-styrene (PA6/ABS) with multiwall carbon nanotubes (MWNTs) were prepared with the intention to develop conducting composites. A generic strategy, namely specific interactions combined with reactive coupling, was adopted to facilitate and to retain the 'network-like' structure of MWNTs during melt-mixing. This was facilitated by the sodium salt of 6-amino hexanoic acid (Na-AHA) and certain phosphonium based modifiers, where it was envisaged that these modifiers would establish specific interactions (either 'cation-π' or 'π-π' ) with the 'π-electron' clouds of MWNTs, as well as restricting them in the PA6 phase of the blends via reactive coupling. This route eventually led to a remarkable increase in the electrical conductivity and dielectric constant in the blends with MWNTs. Raman, FTIR and TEM investigations further supported these observations.