Iron Oxide-Au Magneto-Plasmonic Heterostructures: Advances in Their Eco-Friendly Synthesis

In recent years, nanotechnologies have attracted considerable interest, especially in the biomedical field. Among the most investigated particles, magnetic based on iron oxides and Au nanoparticles gained huge interest for their magnetic and plasmonic properties, respectively. These nanoparticles are usually produced starting from processes and reagents that can be the cause of potential human health and environmental concerns. For this reason, there is a need to develop simple, green, low-cost, and non-toxic synthesis methods and reagents. This review aims at providing an overview of the most recently developed processes to produce iron oxide magnetic nanoparticles, Au nanoparticles, and their magneto-plasmonic heterostructures using eco-friendly approaches, focusing the attention on the microorganisms and plant-assisted syntheses and showing the first results of the development of magneto-plasmonic heterostructures.

Rosehip Extract-Functionalized Magnesium Hydroxide Nanoparticles and Its Effect on Osteoblastic and Osteoclastic Cells

Considering the role of magnesium in bone metabolism and the increasing relevance of plant-mediated green-synthesis, this work compares the bone cytocompatibility of magnesium hydroxide nanoparticles (NPs) produced by using pure water, Mg(OH)₂, or a rosehip (RH) aqueous extract, Mg(OH)₂RH. The NPs were evaluated for dose- and time-dependent effects on human osteoblastic and osteoclastic response, due to the direct involvement of the two cell types in bone metabolism. Mg(OH)₂ NPs presented nanoplatelet-like morphology (mean diameter ~90 nm) and a crystalline structure (XRD analysis); the RH-mediated synthesis yielded smaller rounded particles (mean diameter <10 nm) with decreased crystallinity. On the ATR-FTIR spectra, both NPs presented the characteristic Mg-OH peaks; Mg(OH)₂RH exhibited additional vibration bands associated with the presence of phytochemicals. On osteoblastic cells, NPs did not affect cell growth and morphology but significantly increased alkaline phosphatase (ALP) activity; on osteoclastic cells, particles had little effect in protein content, tartrate-resistant acid phosphatase (TRAP) activity, percentage of multinucleated cells, and cell area. However, compared with Mg(OH)₂, Mg(OH)₂RH increased osteoblastic differentiation by inducing ALP activity and promoting the expression of Runx2, SP7, Col1a1, and ALP, and had a negative effect on the expression of the osteoclastic genes NFATC1, CA2, and CTSK. These observations suggest the potential usefulness of Mg(OH)₂RH NPs in bone regeneration.

Role of pH in the synthesis and growth of gold nanoparticles using L-asparagine: a combined experimental and simulation study

The use of biomolecules as capping and reducing agents in the synthesis of metallic nanoparticles constitutes a promising framework to achieve desired functional properties with minimal toxicity. The system's complexity and the large number of variables involved represent a challenge for theoretical and experimental investigations aiming at devising precise synthesis protocols. In this work, we use L-asparagine (Asn), an amino acid building block of large biomolecular systems, to synthesise gold nanoparticles (AuNPs) in aqueous solution at controlled pH. The use of Asn offers a primary system that allows us to understand the role of biomolecules in synthesising metallic nanoparticles. Our results indicate that AuNPs synthesised in acidic (pH 6) and basic (pH 9) environments exhibit somewhat different morphologies. We investigate these AuNPs via Raman scattering experiments and classical molecular dynamics simulations of zwitterionic and anionic Asn states adsorbing on (111)-, (100)-, (110)-, and (311)-oriented gold surfaces. A combined analysis suggests that the underlying mechanism controlling AuNPs geometry correlates with amine's preferential adsorption over ammonium groups, enhanced upon increasing pH. Our simulations reveal that Asn (both zwitterionic and anionic) adsorption on gold (111) is essentially different from adsorption on more open surfaces. Water molecules strongly interact with the gold face-centred-cubic lattice and create traps, on the more open surfaces, that prevent the Asn from diffusing. These results indicate that pH is a relevant parameter in green-synthesis protocols with the capability to control the nanoparticle's geometry, and pave the way to computational studies exploring the effect of water monolayers on the adsorption of small molecules on wet gold surfaces.

Critical analysis of biophysicochemical parameters for qualitative improvement of phytogenic nanoparticles

Conventional chemical approaches for synthesizing nanoparticles (NPs) may restrict their applicability as they are not eco-friendly, energetically efficient and often involve toxic reducing/capping agents; but phytonanotechnology enabled the synthesis of safe, inexpensive, highly biocompatible NPs. In this regard, thorough understanding of green components and the modulatory effects of different reaction conditions on the physicochemical parameters of green synthesized NPs would be a prerequisite, which is not depicted elsewhere. This review critically analyzes the relevant reaction conditions from their mechanistic viewpoints in plant-based synthesis of NPs arising fundamental issues which need to be determined carefully. The size, stability and surface chemistry of phytogenic NPs may be fabricated as a function of multiple interconnected reaction parameters and the plant species used. The therapeutic potential of phytogenic NPs may depend on the plant species used; and so the meticulous understanding of physicochemical parameters and the family wise shorting of elite plant species may potentially benefit the theranostic future of plant-based NPs.

Silica Nanoparticles for Insect Pest Control

To date, control strategies used against insect pest species are based on synthetic insecticide applications. In addition, the efficacy of these treatments could be decreased due to insecticide resistance in insect populations. Also, the irrational use of chemical control strategies has negative consequences of non-target organisms and threatening human health. Designing nanomaterial for pest insect control is a promising alternative to traditional insecticide formulations. In particular, it has been proven that silica nanoparticles have the potential for molecules delivery, release control improvement and also their toxicity as insecticide alone. In this work, we summarized the state of knowledge on silica nanoparticles (SiNPs) used in pest insect management. Besides, aspects of their synthesis, mode of action, and toxic effects on non-target organisms and environment are reviewed.

Polarclean as a Sustainable Reaction Medium for the Waste Minimized Synthesis of Heterocyclic Compounds

Herein we report the use of Rhodiasolv^© Polarclean as a novel polar aprotic solvent for the synthesis of decorated heterocycles via dipolar cycloaddition (isooxazoles) or intramolecular C–H functionalization processes (benzo-fused chromenes). The use of Polarclean allowed to isolate the final products in good yields by simple solid filtration or liquid-liquid phase separation, avoiding the need for chromatographic purification. Moreover, since in the synthesis of benzo-fused chromenes, the metal catalyst is retained in Polarclean, the catalyst/reaction medium can be easily reused for consecutive reaction runs, without any apparent loss in efficiency. This methodology is associated with a limited waste production. These results extend the applicability of Polarclean as a promising reaction medium for the replacement of toxic petrol-based solvent.

Biosynthesized composites of Au-Ag nanoparticles using Trapa peel extract induced ROS-mediated p53 independent apoptosis in cancer cells

The current study highlights rapid, sustainable, and cost-effective biosynthesis of silver (Ag), gold (Au) nanoparticles (NPs), and bimetallic Au-AgNPs composites using bio-waste extract of Trapa natans. Growth of the NPs was monitored spectrophotometrically and peak was observed at ∼525 nm, ∼450 nm, and ∼495 nm corresponding to Plasmon absorbance of AuNPs, AgNPs, and Au-AgNPs, respectively. Transmission electron microscopy (TEM) revealed the size of AgNPs (∼15 nm), AuNPs (∼25 nm), and Au-AgNPs (∼26-90 nm). Synthesized NPs follow the Gaussian bell curve and its crystalline nature was identified by X-ray diffraction (XRD). Furthermore, Au-AgNPs induced cytotoxicity in various cancer cells (HCT116, MDA-MB-231, and HeLa) effectively at 200 μg/mL. Au-AgNPs-exposed cancer cells exhibited apoptotic features such as nuclear condensation, mitochondrial membrane potential loss, and cleavage of casp-3 and poly (ADP-ribose) polymerase-1 (PARP). Au-AgNPs exposure enhanced reactive oxygen species (ROS) and upon inhibition of ROS, apoptosis was reduced effectively. NPs treatment killed HCT116 WT and p53 knockout cells without any significant difference. Mechanistically, Au-AgNPs derived with Trapa peel extract significantly enhance ROS which trigger p53-independent apoptosis in various cancer cells effectively. Our study explores the use of bio-waste for the green synthesis of NPs, which can be attractive candidates for cancer therapy.

Synthesis of Titanium Dioxide Nanoparticles Using Echinacea purpurea Herba

Nowadays green synthesis of metal nanoparticles is a developing area of research. In this study, titanium dioxide nanoparticles were biosynthesized using an aqueous solution of Echinacea purpurea herba extract as a bioreductant. This is novel and interesting method for synthesis of TiO₂ nanoparticles. The prepared titanium dioxide nanoparticles were characterized using ultraviolet-visible spectroscopy (UV-VIS), transmission electron microscopy (SEM), total reflection X-Ray fluorescence analysis (TXRF) and Fourier-transform infrared spectroscopy (FTIR). The size of TiO₂ nanoparticles was found to be in the range of 120 nm. Moreover, the alkaline reaction of the solution (pH = 8) resulted in the increase in absorbance (280 nm), which facilitates the growth of the number of TiO₂ nanoparticles in the studied solution. Also, synthesis of TiO₂ nanoparticles using green resources like Echinacea purpurea herba is a better alternative to chemical synthesis, since this green synthesis is pollutant-free and eco-friendly.