Multifaceted prospects of nanocomposites for cardiovascular grafts and stents

Vascular Repair by Grafting Based on Magnetic Nanoparticles

Magnetic nanoparticles (MNPs) have attracted much attention in the past few decades because of their unique magnetic responsiveness. Especially in the diagnosis and treatment of diseases, they are mostly involved in non-invasive ways and have achieved good results. The magnetic responsiveness of MNPs is strictly controlled by the size, crystallinity, uniformity, and surface properties of the synthesized particles. In this review, we summarized the classification of MNPs and their application in vascular repair. MNPs mainly use their unique magnetic properties to participate in vascular repair, including magnetic stimulation, magnetic drive, magnetic resonance imaging, magnetic hyperthermia, magnetic assembly scaffolds, and magnetic targeted drug delivery, which can significantly affect scaffold performance, cell behavior, factor secretion, drug release, etc. Although there are still challenges in the large-scale clinical application of MNPs, its good non-invasive way to participate in vascular repair and the establishment of a continuous detection process is still the future development direction.

Iron Oxide Nanoparticles in Regenerative Medicine and Tissue Engineering

In recent years, many promising nanotechnological approaches to biomedical research have been developed in order to increase implementation of regenerative medicine and tissue engineering in clinical practice. In the meantime, the use of nanomaterials for the regeneration of diseased or injured tissues is considered advantageous in most areas of medicine. In particular, for the treatment of cardiovascular, osteochondral and neurological defects, but also for the recovery of functions of other organs such as kidney, liver, pancreas, bladder, urethra and for wound healing, nanomaterials are increasingly being developed that serve as scaffolds, mimic the extracellular matrix and promote adhesion or differentiation of cells. This review focuses on the latest developments in regenerative medicine, in which iron oxide nanoparticles (IONPs) play a crucial role for tissue engineering and cell therapy. IONPs are not only enabling the use of non-invasive observation methods to monitor the therapy, but can also accelerate and enhance regeneration, either thanks to their inherent magnetic properties or by functionalization with bioactive or therapeutic compounds, such as drugs, enzymes and growth factors. In addition, the presence of magnetic fields can direct IONP-labeled cells specifically to the site of action or induce cell differentiation into a specific cell type through mechanotransduction.

Toward Innovative Hemocompatible Surfaces: Crystallographic Plane Impact on Platelet Activation

The anticoagulation treatment of cardiovascular patients, which is mandatory after implantation of heart valves or stents, has significantly adverse effects on life quality. This treatment can be reduced or even circumvented by developing novel antithrombogenic surfaces of blood-contacting implants. Thus, we aim to discover materials exhibiting outstanding hemocompatibility compared to other available synthetic materials. We present promising surficial characteristics of single crystalline alumina in terms of platelet activation inhibition. In order to elucidate the relation between its crystallographic properties including the plane orientation and blood cell behavior, we examined endothelialization, cytocompatibility, and platelet activation at the blood-alumina interfaces in a controlled experimental setup. We observed that the cell response is highly sensitive to the plane orientation and differs significantly for (0001) and (11-20) planes of Al₂O₃. Our results reveal for the first time the dependence of platelet activation on crystallographic orientation, which is assumed to be a critical condition controlling the thrombogenicity. Additionally, we used an endothelial cell monolayer as an internal control since endothelial cells have an impact on vessel integrity and implant acceptance. We successfully demonstrate that Al₂O₃(11-20) exhibits enhanced hemocompatibility in contrast to Al₂O₃(0001) and is comparable to the physiological endothelial monolayer in vitro.

Bacterial cellulose membrane functionalized with hydroxiapatite and anti-bone morphogenetic protein 2: A promising material for bone regeneration

Bone tissue engineering seeks to adequately restore functions related to physical and biological properties, aiming at a repair process similar to natural bone. The use of compatible biopolymers, such as bacterial cellulose (BC), as well as having interesting mechanical characteristics, presents a slow in vivo degradation rate, and the ability to be chemically modified. To promote better bioactivity towards BC, we synthesized an innovative BC membrane associated to hydroxyapatite (HA) and anti-bone morphogenetic protein antibody (anti-BMP-2) (BC-HA-anti-BMP-2). We present the physical-chemical, biological and toxicological characterization of BC-HA-anti-BMP-2. Presence of BC and HA components in the membranes was confirmed by SEM-EDS and FTIR assays. No toxic potential was found in MC3T3-E1 cells by cytotoxicity assays (XTT Assay and Clonogenic Survival), genotoxicity (Comet Assay) and mutagenicity (Cytokinesis-blocked micronucleus Test). The in vitro release kinetics of anti-BMP-2 antibodies detected gradually reducing antibody levels, reducing approximately 70% in 7 days and 90% in 14 days. BC-HA-anti-BMP-2 increased SPP1, BGLAP, VEGF, ALPL, RUNX2 and TNFRSF11B expression, genes involved in bone repair and also increased mineralization nodules and phosphatase alcalin (ALP) activity levels. In conclusion, we developed BC-HA-anti-BMP-2 as an innovative and promising biomaterial with interesting physical-chemical and biological properties which may be a good alternative to treatment with commercial BMP-2 protein.

Influence of Different Acids on the Transport of CdSe Quantum Dots from Polymer Nanocomposites to Food Simulants

We fabricated polymer nanocomposites (PNCs) from low-density polyethylene and CdSe quantum dots (QDs) and used these materials to explore potential exposure after long-term storage in different acidic media that could be encountered in food contact applications. While the low-level release of QD-associated mass into all the food simulants was observed, exposure to dilute acetic acid resulted in more than double the mass transfer compared to that which occurred during exposure to dilute hydrochloric acid at the same pH. Conversely, exposure to citric acid resulted in a suppression of QD release. Permeation experiments and confocal microscopy were used to reveal mechanistic details underlying these mass-transfer phenomena. From this work, we conclude that the permeation of undissociated acid molecules into the polymer, limited by partitioning of the acids into the hydrophobic polymer, plays a larger role than pH in determining exposure to nanoparticles embedded in plastics. Although caution must be exercised when extrapolating these results to PNCs incorporating other nanofillers, these findings are significant because they undermine current thinking about the influence of pH on nanofiller release phenomena. From a regulatory standpoint, these results also support current guidance that 3% acetic acid is an acceptable acidic food simulant for PNCs fabricated from hydrophobic polymers because the other acids investigated resulted in significantly less exposure.

Heterogeneity of Scaffold Biomaterials in Tissue Engineering

Tissue engineering (TE) offers a potential solution for the shortage of transplantable organs and the need for novel methods of tissue repair. Methods of TE have advanced significantly in recent years, but there are challenges to using engineered tissues and organs including but not limited to: biocompatibility, immunogenicity, biodegradation, and toxicity. Analysis of biomaterials used as scaffolds may, however, elucidate how TE can be enhanced. Ideally, biomaterials should closely mimic the characteristics of desired organ, their function and their in vivo environments. A review of biomaterials used in TE highlighted natural polymers, synthetic polymers, and decellularized organs as sources of scaffolding. Studies of discarded organs supported that decellularization offers a remedy to reducing waste of donor organs, but does not yet provide an effective solution to organ demand because it has shown varied success in vivo depending on organ complexity and physiological requirements. Review of polymer-based scaffolds revealed that a composite scaffold formed by copolymerization is more effective than single polymer scaffolds because it allows copolymers to offset disadvantages a single polymer may possess. Selection of biomaterials for use in TE is essential for transplant success. There is not, however, a singular biomaterial that is universally optimal.

Polyacrylate/nanosilica causes pleural and pericardial effusion, and pulmonary fibrosis and granuloma in rats similar to those observed in exposed workers

Nanomaterials offer great benefit as well as potential damage to humans. Workers exposed to polyacrylate coatings have pleural effusion, pericardial effusion, and pulmonary fibrosis and granuloma, which are thought to be related to the high exposure to nanomaterials in the coatings. The study aimed to determine whether polyacrylate/silica nanoparticles cause similar toxicity in rats, as observed in exposed workers. Ninety male Wistar rats were randomly divided into five groups with 18 rats in each group. The groups included the saline control group, another control group of polyacrylate only, and low-, intermediate-, and high-dose groups of polyacrylate/nanosilica with concentrations of 3.125, 6.25, and 12.5 mg/kg. Seventy-five rats for the 1-week study were terminated for scheduled necropsy at 24 hours, 3 days, and 7 days postintratracheal instillation. The remaining 15 rats (three males/group) had repeated ultrasound and chest computed tomography examinations in a 2-week study to observe the pleural and pericardial effusion and pulmonary toxicity. We found that polyacrylate/nanosilica resulted in pleural and pericardial effusions, where nanosilica was isolated and detected. Effusion occurred on day 3 and day 5 post-administration of nanocomposites in the 6.25 and 12.5 mg/kg groups, it gradually rose to a maximum on days 7-10 and then slowly decreased and disappeared on day 14. With an increase in polyacrylate/nanosilica concentrations, pleural effusion increased, as shown by ultrasonographic qualitative observations. Pulmonary fibrosis and granuloma were also observed in the high-dose polyacrylate/nanosilica group. Our study shows that polyacrylate/nanosilica results in specific toxicity presenting as pleural and pericardial effusion, as well as pulmonary fibrosis and granuloma, which are almost identical to results in reported patients. These results indicate the urgent need and importance of nanosafety and awareness of toxicity of polyacrylate/nanosilica.

Unravelling the potential of nitric acid as a surface modifier for improving the hemocompatibility of metallocene polyethylene for blood contacting devices

Design of blood compatible surfaces is obligatory to minimize platelet surface interactions and improve the thromboresistance of foreign surfaces when they are utilized as biomaterials particularly for blood contacting devices. Pure metallocene polyethylene (mPE) and nitric acid (HNO3) treated mPE antithrombogenicity and hydrophilicity were investigated. The contact angle of the mPE treated with HNO3 decreased. Surface of mPE and HNO3 treated mPE investigated with FTIR revealed no major changes in its functional groups. 3D Hirox digital microscopy, SEM and AFM images show increased porosity and surface roughness. Blood coagulation assays prothrombin time (PT) and activated partial thromboplastin time (APTT) were delayed significantly (P < 0.05) for HNO3 treated mPE. Hemolysis assay and platelet adhesion of the treated surface resulted in the lysis of red blood cells and platelet adherence, respectively indicating improved hemocompatibility of HNO3 treated mPE. To determine that HNO3 does not deteriorate elastic modulus of mPE, the elastic modulus of mPE and HNO3 treated mPE was compared and the result shows no significant difference. Hence, the overall observation suggests that the novel HNO3 treated mPE may hold great promises to be exploited for blood contacting devices like grafts, catheters, and etc.