Magnetic 3D cell culture: State of the art and current advances.

Cell culture is an important tool for the understanding of cell biology and behavior. In vitro cultivation has been increasingly indispensable for biomedical, pharmaceutical, and biotechnology research. Nevertheless, with the demand for in vitro experimentation strategies more representative of in vivo conditions, tridimensional (3D) cell culture models have been successfully developed. Although these 3D models are efficient and address critical questions from different research areas, there are considerable differences between the existing techniques regarding both elaboration and cost. In light of this, this review describes the construction of 3D spheroids using magnetization while bringing the most recent updates in this field. Magnetic 3D cell culture consists of magnetizing cells using an assembly of gold and iron oxide nanoparticles cross-linked with poly-l-lysine nanoparticles. Then, 3D culture formation in special plates with the assistance of magnets for levitation or bioprinting. Here, we discuss magnetic 3D cell culture advancements, including tumor microenvironment, tissue reconstruction, blood vessel engineering, toxicology, cytotoxicity, and 3D culture of cardiomyocytes, bronchial and pancreatic cells.

A Study of the Effects of pH and Surfactant Addition on Gold Nanoparticle Aggregation.

Gold nanoparticles (AuNPs) can provide a simple, easy-to-use, inexpensive, at hand point-of-care (POC) fast to diagnose; however, AuNPs have the predisposition to form aggregations. Since the nanoparticles stability is an important issue, this article is aiming to study the long-term stability associated with the development of an immunosensor for clinical diagnosis. Here, we assessed two previous methods commonly described in the literature to prevent the formation of aggregate by studying pH and Tween® 20 (polysorbates) addition as surfactant. AuNPs were characterized through ultraviolet-visible (UV-Vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM) and through analysis in the ImageJ software. We found that the Tween® 20 provided more than stable condition in aqueous solution in comparison to pH dependence. The fabricated AuNPs were further used to detect dengue virus and demonstrating that its use at pH 7.2 did not maintain reproducibility in the detection of dengue virus after one year. Unlike, the Tween® 20 modified AuNPs that detected dengue virus soon after the synthesis and over the course of one year demonstrating the high sensitivity of immunosensor. Finally, our result showed excellent dispersity throughout the year when using Tween® 20 to avoid aggregation.

Antibacterial and anti-biofilm activities of cinnamaldehyde against S. epidermidis.

The search for new antimicrobial drugs has been necessary due to the increased bacterial resistance to antibiotics currently in use, and natural products play an important role in this field. The aim of this study was to evaluate the in vitro effect of cinnamaldehyde on S. epidermidis strains, biofilm set-up prevention, as well as its effect on pre-established biofilms. The minimum inhibitory concentration (MIC) ranged from 300 to 500 µg/mL, and the minimum bactericidal concentration (MBC) from 400 to 600 µg/mL. The biofilm inhibitory concentration and biofilm eradication concentration values were four-fold (clinical isolate) and eight-fold (ATCC strain) greater than the concentration required to inhibit planktonic growth. Sub-inhibitory concentrations of cinnamaldehyde attenuated biofilm formation of S. epidermidis strains on polystyrene microtiter plates. The combination of cinnamaldehyde and linezolid was able to inhibit S. epidermidis with a bactericidal effect. Further investigation of the mechanism of action of cinnamaldehyde revealed its effect on the cell membrane permeability, and confocal laser scanning microscopy (CLSM) images illustrated the impact of cinnamaldehyde in the detachment and killing of existing biofilms. Thereby, our data confirmed the ability of cinnamaldehyde to reduce bacterial planktonic growth of S. epidermidis, inhibiting biofilm formation and eradicating pre-formed biofilm.