Janja Stergar

Review of aerogel-based materials in biomedical applications

Due to their many excellent properties, aerogels attract much interest in various applications, ranging from construction to medicine. Over the last decades, their potential was practically exploited only in non-medical fields of use, although many aerogel materials, either organic, inorganic or hybrid, were proven biocompatible. Some aerogel compositions have been patented at the verge of the millennium, but the clinical use of aerogels remains very limited. This review intends to shed some more light in regard to their potential in biomedical applications as can be deduced from the more recent progressive research of their capabilities in regard to different compositions. The review covers many recent studies, but includes older research that significantly affected the development of aerogel-based materials over the years, as well. After a short introduction, covering the common aerogel properties and their possible classification options, the review is structured based on their different possible biomedical applications. Finally, it focuses on the potential of aerogels in regenerative medicine.Graphical Abstract

Novel chitosan/diclofenac coatings on medical grade stainless steel for hip replacement applications

Corrosion resistance, biocompatibility, improved osteointegration, as well the prevention of inflammation and pain are the most desired characteristics of hip replacement implants. In this study we introduce a novel multi-layered coating on AISI 316LVM stainless steel that shows promise with regard to all mentioned characteristics. The coating is prepared from alternating layers of the biocompatible polysaccharide chitosan and the non-steroid anti-inflammatory drug (NSAID), diclofenac. Electrochemical methods were employed to characterize the corrosion behavior of coated and uncoated samples in physiological solution. It is shown that these coatings improve corrosion resistance. It was also found that these coatings release the incorporated drug in controlled, multi-mechanism manner. Adding additional layers on top of the as-prepared samples, has potential for further tailoring of the release profile and increasing the drug dose. Biocompatibility was proven on human-derived osteoblasts in several experiments. Only viable cells were found on the sample surface after incubation of the samples with the same cell line. This novel coating could prove important for prolongation of the application potential of steel-based hip replacements, which are these days often replaced by more expensive ceramic or other metal alloys.

Synthesis and Characterization of Silica-Coated Cu

The synthesis of magnetic Cu1-xNix nanoparticles was carried out in cationic water-in-oil (w/o) microemulsions of water/cetyl-trimethyl-ammonium bromide (CTAB), n-butanol/isooctane by the reduction of nickel and copper chlorides with hydrazine and NaOH. The synthesized Cu1-xNix particles were heat treated to maintain their proper homogeneity and Curie temperature. Some alloy particles with the composition CU27.5M72.5 were coated with silica prior to the thermal homogenization in order to retain the pristine morphology. The magnetic particles were characterized using XRD, transmission electron microscopy (TEM) and magnetic measurements. The thermal demagnetization in the vicinity of the Curie temperature of the nanoparticles was studied using a modified TGA/SDTA method.

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In the past two decades, several novel nanoparticles (NPs) were shown to have great potential to be used as drug delivering systems. This is especially true for superparamagnetic nanoparticles (MNPs), which exhibit their magnetic properties only when there is an influence of external magnetic fields. These have received much attention in the last couple of years due to a relatively simple chemical structure, ease of preparation, possible preparation in various shapes and very small sizes, as well due to their favorable properties in biomedical applications (e.g., biocompatibility). Controlled drug delivery systems have several advantages compared to traditional pharmaceutical formulations. For example, these can enable drug transportation to the desired site of action in the body, through which, its influence on healthy tissues, as well as unwanted effects, can be minimized. Such form of delivery is most important in case of drugs with a very narrow therapeutic index or if the drug itself is a toxic compound as is the case in many antitumor drugs. In this study, we prepared a novel controlled drug delivery formulation using the sol–gel procedure, composed of Ni67.5Cu32.5 MNPs in a silica matrix. As the model drug, we used the fluorescent dye rhodamine 6G (RHO6G) to ease the evaluation of the delivery performance to various human cells (human fibroblast cell line, HeLa cells, and Caco-2 cells). The drug release performance was assessed also using in vitro drug release studies. The combination of different physico-chemical and morphological methods with biocompatibility studies served as a general evaluation of the novel formulations safety and efficiency. Graphical abstractGraphical abstract

Ni

Local drug delivery systems made from nontoxic polysaccharide nanofilms have an enormous potential in wound care. A detailed understanding of the structural, surface, physicochemical, and cytotoxic properties of such systems is crucial to design clinically efficacious materials. Herein, we fabricated polysaccharide-based nanofilms onto either a 2D model (SiO2 and Au sensors) or on nonwoven alginate 3D substrates using an alternating assembly of N,N,N-trimethylchitosan (TMC) and alginic acid (ALG) by a spin-assisted layer-by-layer (LbL) technique. These TMC/ALG multilayered nanofilms are used for a uniform encapsulation and controlled release of pentoxifylline (PTX), a potent anti-inflammatory drug for treatment of the chronic venous ulceration. We show a tailorable film growth and mass, morphology, as well as surface properties (charge, hydrophilicity, porosity) of the assembled nanofilms through control of the coating during the spin-assisted assembly. The uniform distribution of the encapsulated PTX in the TMC/ALG nanofilms is preserved even with when the amount of the incorporated PTX increases. The PTX release mechanism from the model and real systems is studied in detail and is very comparable for both systems. Finally, different cell-based assays illustrated the potential of the TMC/ALG multilayer system in wound care (e.g., treatment chronic venous ulceration) applications, including a decrease of TNF-α secretion, a common indicator of inflammation.

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Abstract Magnetic nanoparticles (MNPs) have attracted extensive interest in recent years because of their unique magnetic, electronic, catalytical, optical, and chemical properties. Lately, research on bimetallic MNPs based on nickel and copper (NiCu MNPs) gained momentum owing to their desired properties for use in biomedicine, such as their chemical stability, biocompatibility, and highly tunable magnetic properties by means of synthesis parameter tuning. The general interest of using NiCu MNPs in biomedical applications is still low, although it is steadily increasing as can be deduced from the number of related publications in the last years. When exposed to an alternating magnetic field (AMF), superparamagnetic particles (such as NiCu MNPs) generate heat by relaxation losses. Consequently, magnetic hyperthermia in cancer treatment seems to be their most promising application in medicine, although others are emerging as well, such as their use to guide potent drugs to the targeted site or to prolong their localization at a desired site in the body. This review is the first, to the best of our knowledge, that covers the available knowledge related to the preparation of NiCu MNPs using different methods, their resulting properties, and the already developed functionalization methods and that discusses everything mentioned in relation to their possible applicability in biomedicine.