Production of nanostructured systems: Main and innovative techniques.

In the constant search for the development of more-specific and more-selective drugs, especially with regard to the challenge of encapsulating hydrophilic molecules, polymer nanotechnologies are remarkable for their biocompatible and biodegradable properties. The most-used nanoencapsulation methods consist of emulsification procedures, where emulsified droplets of a given polymer and drug solidify into nanoparticles after solvent extraction from the polymeric phase. This review introduces conventional emulsification methods but also highlights new emulsification technologies such as microfluidics, membrane emulsification and other techniques, including spray drying, inkjet printing and electrospraying.

Association of electrospinning with electrospraying: a strategy to produce 3D scaffolds with incorporated stem cells for use in tissue engineering.

In tissue engineering, a uniform cell occupation of scaffolds is crucial to ensure the success of tissue regeneration. However, this point remains an unsolved problem in 3D scaffolds. In this study, a direct method to integrate cells into fiber scaffolds was investigated by combining the methods of electrospinning of fibers and bioelectrospraying of cells. With the associating of these methods, the cells were incorporated into the 3D scaffolds while the fibers were being produced. The scaffolds containing cells (SCCs) were produced using 20% poly(lactide-co-glycolide) solution for electrospinning and mesenchymal stem cells from deciduous teeth as a suspension for bioelectrospraying. After their production, the SCCs were cultivated for 15 days at 37°C with an atmosphere of 5% CO2. The 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide test demonstrated that the cells remained viable and were able to grow between the fibers. Scanning electron microscopy showed the presence of a high number of cells in the structure of the scaffolds and confocal images demonstrated that the cells were able to adapt and spread between the fibers. Histological analysis of the SCCs after 1 day of cultivation showed that the cells were uniformly distributed throughout the thickness of the scaffolds. Some physicochemical properties of the scaffolds were also investigated. SCCs exhibited good mechanical properties, compatible with their handling and further implantation. The results obtained in the present study suggest that the association of electrospinning and bioelectrospraying provides an interesting tool for forming 3D cell-integrated scaffolds, making it a viable alternative for use in tissue engineering.

Nanofiber scaffolds support bone regeneration associated with pulp stem cells.

Currently, there are a number of alternatives for bone grafting, though when used correctly they present physical, chemical or biological limitations, which justifies the pursuit for new alternatives for bone regeneration. This study gives a report on the potential for bone regeneration in the use of biodegradable nanofibers from poly (lactic-co-glycolic acid) (PLGA) in association with human mesenchymal stem cells from dental pulp of deciduous teeth (SCDT). Five samples of SCDT were seeded with scaffolds (test) or without scaffolds (control) for cell adhesion and viability assay. To evaluate the ability of the association in promoting bone formation, critical defects were made in the calvarium of rats (n=20), which were then divided into the following groups: I--sham group; II--implant of scaffolds; III--scaffolds/ SCDT; and IV--scaffolds/SCDT. They were kept for 13 days in osteogenic media. After 60 days, the histomorphometric analysis was performed. It was observed that the adherence and viability of SCDT in the control and test group were similar throughout the experiment (p>0.05). The association of scaffolds/SCDT maintained in osteogenic media, showed greater bone formation than the other groups (p<0.05). The study demonstrated that the association of SCDT seeded in biodegradable PLGA scaffolds has the ability to promote bone regeneration in rats, which is a promising alternative for application in regenerative medicine.

The effect of sterilization methods on electronspun poly(lactide-co-glycolide) and subsequent adhesion efficiency of mesenchymal stem cells.

The sterilization of scaffolds is an essential step for tissue engineering in vitro and, mainly, clinical biomaterial use. However, this process can cause changes in the structure and surface of the scaffolds. Therefore, the objective of this study was to investigate the effect of sterilization by ethanol, ultraviolet radiation (UVR) or antimicrobial solution (AMS) on poly(lactide-co-glycolide) (PLGA) scaffolds produced by the electrospinning technique. The properties of nanofibers and the cellular adhesion of mesenchymal stem cells to the scaffolds were analyzed after the treatments. All methods generated sterile scaffolds but showed some kind of damage to the scaffolds. Ethanol and AMS caused changes in the morphology and scaffold dimensions, which were not observed when using the UVR method. However, UVR caused a greater reduction in polymeric molecular weight, which increased proportionally with exposure time of treatment. Nanofibers sterilized with AMS for 1 h and 2 h showed greater cellular adhesion than the other methods, demonstrating their potential as a method for sterilizing PLGA nanofibers.

Novel chemically modified bacterial cellulose nanocomposite as potential biomaterial for stem cell therapy applications.

Bacterial cellulose (BC) has become established as a remarkably versatile biomaterial and can be used in a wide variety of applied scientific applications, especially for medical devices. In this work, the bacterial cellulose fermentation process is modified by the addition of hyaluronic acid and gelatin (1% w/w) to the culture medium before the bacteria is inoculated. Hyaluronic acid and gelatin influence in bacterial cellulose was analyzed using Transmission Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Adhesion and viability studies with human dental pulp stem cells using natural bacterial cellulose/hyaluronic acid as scaffolds for regenerative medicine are presented for the first time in this work. MTT viability assays show higher cell adhesion in bacterial cellulose/gelatin and bacterial cellulose/ hyaluronic acid scaffolds over time with differences due to fiber agglomeration in bacterial cellulose/gelatin. Confocal microscopy images showed that the cell were adhered and well distributed within the fibers in both types of scaffolds.