We studied the controlled growth of triangular prismatic Au nanoparticles with different beveled sides for surface-enhanced Raman spectroscopy (SERS) applications. First, in a seedless synthesis using 3-butenoic acid (3BA) and benzyldimethylammonium chloride (BDAC), gold nanotriangles (AuNTs) were synthesized in a mixture with gold nanooctahedra (AuNOCs) and separated by depletion-induced flocculation. Here, the influence of temperature, pH, and reducing agent on the reaction kinetics was initially investigated by UV-vis and correlated to the size and yield of AuNT seeds. In a second step, the AuNT size was increased by seed-mediated overgrowth with Au. We show for the first time that preformed 3BA-synthesized AuNT seeds can be overgrown up to a final edge length of 175 nm and a thickness of 80 nm while maintaining their triangular shape and tip sharpness. The NT morphology, including edge length, thickness, and tip rounding, was precisely characterized in dispersion by small-angle X-ray scattering and in dry state by transmission electron microscopy and field-emission scanning electron microscopy. For sensor purposes, we studied the size-dependent SERS performance of AuNTs yielding analytical enhancement factors between 0.9 × 10 and 5.6 × 10 and nanomolar limit of detection (10-10 M) for 4-mercaptobenzoic acid and BDAC. These results confirm that the 3BA approach allows the fabrication of AuNTs in a whole range of sizes maintaining the NT morphology. This enables tailoring of localized surface plasmon resonances between 590 and 740 nm, even in the near-infrared window of a biological tissue, for use as colloidal SERS sensing agents or for optoelectronic applications.
Here, temperature-sensitive hybrid poly(N-isopropylacrylamide) (pNIPAM) nanosystems with magnetic response are synthesised and investigated for controlled release of 5-fluorouracil (5FU) and oxaliplatin (OXA). Initially, magnetic nanoparticles (@Fe 3 O 4 ) are synthesised by co-precipitation approach and functionalised with acrylic acid (AA), 3-butenoic acid (3BA) or allylamine (AL) as comonomers. The thermoresponsive polymer is grown by free radical polymerisation using N-isopropylacrylamide (NIPAM) as monomer, N,N'-methylenbisacrylamide (BIS) as cross-linker, and 2,2'-azobis(2-methylpropionamidene) (V50) as initiator. We evaluate particle morphology by transmission electron microscopy (TEM) and particle size and surface charge by dynamic light scattering (DLS) and Z-potential (ZP) measurements. These magnetically active pNIPAM@ nanoformulations are loaded with 5-fluorouracil (5FU) and oxaliplatin (OXA) to determine loading efficiency, drug content and release as well as the cytotoxicity against T-84 colon cancer cells. Our results show high biocompatibility of pNIPAM nanoformulations using human blood cells and cultured cells. Interestingly, the pNIPAM@Fe 3 O 4 -3BA þ 5FU nanoformulation significantly reduces the growth of T-84 cells (57% relative inhibition of proliferation). Indeed, pNIPAM-co-AL@Fe 3 O 4 -AA nanosystems produce a slight migration of HCT15 cells in suspension in the presence of an external magnetic field. Therefore, the obtained hybrid nanoparticles can be applied as a promising biocompatible nanoplatform for the delivery of 5FU and OXA in the improvement of colon cancer treatments.
We report the green synthesis of silver nanoparticles (AgNPs) by using daisy petals (Bellis perennis), leek (Allium porrum) and garlic skin (Allium sativum) as reducing agents and water as solvent. AgNPs are obtained with high monodispersity, spherical shapes and size ranging from 5 to 35 nm and characterized by UV-Vis and TEM techniques. The obtained yields in AgNPs are in concordance with the total phenolic content of each plant. We also study the incorporation of AgNPs in combination with the red algae Pyropia columbina extracts (PCE) into cosmetic formulations and analyze their combined effect as photoprotective agents. Moreover, we carry out the inclusion of the PCE containing mycosporine-like amino acids (MAAs), which are strong UV-absorbing and antioxidant compounds, into β-cyclodextrin (βCD) and pNIPAM nanoparticles and analyze stability and release. The thermoresponsive polymer is grown by free radical polymerization using N-isopropylacrylamide (NIPAM) as the monomer, N,N′-methylenebisacrylamide (BIS) as the cross-linker, and 2,2′-azobis(2-methylpropionamidene) (V50) as the initiator, while βCD complex is prepared by heating in water. We evaluate the nanoparticle and βCD complex formation by UV-Vis and FT-IR, and NMR spectroscopies, respectively, and the nanoparticles’ morphology, including particle size, by TEM. The cosmetic formulations are subsequently subjected to accelerated stability tests and photoprotective analyses: a synergistic effect in the combination of AgNPs and PCE in photoprotection was found. It is not related to a UV screen effect but to the antioxidant activity, having potential against photoaging.
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