Antibacterial and angiogenic potential of iron oxide nanoparticles-stabilized acrylate-based scaffolds for bone tissue engineering applications

Pickering emulsion polymerization, stabilized by inorganic nanoparticles such as iron oxide nanoparticles (IONPs), can be used to fabricate scaffolds with the desired porosity and pore size. These nanoparticles create stable emulsions that can be processed under harsh polymerization conditions. IONPs, apart from serving as an emulsifier, impart beneficial bioactivities such as antibacterial and pro-angiogenic activity. Here, we coated IONPs with three different weights of oleic acid (5.0 g, 7.5 g, and 10.0 g) to synthesize oleic acid-IONPs (OA-IONPs) that possess the desired hydrophobicity (contact angle > 100°). Next, glycidyl methacrylate and trimethylolpropane triacrylate were polymerized using the Pickering emulsion polymerization technique stabilized by the OA-IONPs. The physicochemical properties of the resulting porous scaffolds were thoroughly characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), and a universal testing machine (UTM). The SEM images confirmed the formation of a porous scaffold. The IONPs content, measured using inductively coupled plasma mass spectrometry (ICP-MS), was in the range of 22-26 µg/mg of the scaffold. The mechanical strengths of the scaffolds were in the range of cancellous bone. The degradation profile of the scaffolds varied between 29% and 41% degradation over 30 days. In vitro cytotoxicity studies conducted using the fibroblast (L929) and osteosarcoma (MG-63) cell lines proved that these scaffolds were non-toxic. SEM images showed that the MG-63 cells adhered firmly to the scaffolds and exhibited a well-spread morphology. The antibacterial activity was confirmed by percentage inhibition studies, SEM analysis of bacterial membrane distortion, and reactive oxygen species (ROS) generation in the bacteria. Chick chorioallantoic membrane assay showed that the total vessel length and branch points were significantly increased in the presence of the scaffolds. These results confirm the pro-angiogenic potential of the fabricated scaffolds. The physicochemical, mechanical, and biological properties of the material suggest that the developed scaffolds would be suitable for bone tissue engineering applications.

A review of the genotoxic, mutagenic, and carcinogenic potentials of several lower acrylates

Lower alkyl acrylate monomers include methyl-, ethyl-, n-butyl-, and 2-ethylhexyl acrylate. These acrylates are used in the manufacture of acrylic polymers and copolymers for plastics, food packaging, adhesives, and cosmetic formulations. Although there is limited potential for human environmental exposure, occupational exposure can occur via inhalation and dermal contact. Recently, new genotoxicity data have been generated, along with in silico and in vitro read-cross analyses, for these acrylates. The availability of high-throughput screening (HTS) data through the ToxCast™/Tox21 databases allows for consideration of computational toxicology and organization of these data according to the ten key characteristics of carcinogens. Therefore, we conducted a comprehensive review to evaluate the mechanistic, toxicokinetic, animal, and human data, including HTS data, for characterizing the potential carcinogenicity, mutagenicity, and genotoxicity of these acrylates. Toxicokinetic data demonstrate that these acrylates are metabolized rapidly by carboxylesterase hydrolysis and conjugation with glutathione. HTS data demonstrated an overall lack of bioactivity in cancer-related pathways. Overall, the genotoxicity and mutagenicity data support a cytotoxic, non-genotoxic mechanism for these acrylates. Cancer bioassay studies conducted by the oral, dermal, and inhalation routes in animal models with these acrylates did not show any increase in tumor incidence, with two exceptions. At high doses, and secondary to chronic site-of-contact irritation and corrosion, rodent forestomach tumors were induced by oral gavage dosing with ethyl acrylate, and skin tumors were observed following chronic dermal dosing with 2-ethylhexyl acrylate in C3H/HeJ inbred mice (a strain with deficiencies in wound healing), but not in the outbred NMRI strain. For both dermal and forestomach cancers, tumorigenesis is secondary to high doses and long-term tissue damage, shown to be reversible. With evidence that these chemicals are not genotoxic, and that they cause forestomach and dermal tumors through chronic irritation and regenerative proliferation mechanisms, these acrylates are unlikely to pose a human cancer hazard.