Effect of UV and Gamma Irradiation Sterilization Processes in the Properties of Different Polymeric Nanoparticles for Biomedical Applications.

The sterilization processes of nanoparticles (NP) by autoclaving and filtration are two of the most utilized methods in the pharmaceutical industry but are not always a viable option. For this reason, the search for alternative options such as UV and gamma radiation is of interest. In this work, we evaluated both types of sterilization on two types of NP in solid state widely employed in the literature for biomedical applications, poly-(ε-caprolactone) and poly(D, L-lactide-co-glycolide) acid NP stabilized with polyvinyl alcohol. Physicochemical properties and cell viability were studied pre- and post-sterilization. The efficiency of irradiation sterilization was performed by a test of sterility using 1 × 108 CFU/mL of Escherichia coli, Staphylococcus aureus, and Candida albicans. Microbiological monitoring revealed that both methods were sufficient for sterilization. After the UV irradiation sterilization (100 µJ/cm2), no substantial changes were observed in the physicochemical properties of the NP or in the interaction or morphology of human glial cells, though 5 and 10 kGy of gamma irradiation showed slight changes of NP size as well as a decrease in cell viability (from 100 µg/mL of NP). At 5 kGy of radiation doses, the presence of trehalose as cryoprotectant reduces the cell damage with high concentrations of NP, but this did not occur at 10 kGy. Therefore, these methods could be highly effective and low-processing-time options for sterilizing NP for medical purposes. However, we suggest validating each NP system because these generally are of different polymer-composition systems.

Polycaprolactone- and polycaprolactone/ceramic-based 3D-bioplotted porous scaffolds for bone regeneration: A comparative study.

One of the critical challenges that scaffolding faces in the organ and tissue regeneration field lies in mimicking the structure, and the chemical and biological properties of natural tissue. A high-level control over the architecture, mechanical properties and composition of the materials in contact with cells is essential to overcome such challenge. Therefore, definition of the method, materials and parameters for the production of scaffolds during the fabrication stage is critical. With the recent emergence of rapid prototyping (RP), it is now possible to create three-dimensional (3D) scaffolds with the essential characteristics for the proliferation and regeneration of tissues, such as porosity, mechanical strength, pore size and pore interconnectivity, and biocompatibility. In this study, we employed 3D bioplotting, a RP technology, to fabricate scaffolds made from (i) pure polycaprolactone (PCL) and (ii) a composite based on PCL and ceramic micro-powder. The ceramics used for the composite were bovine bone filling Nukbone® (NKB), and hydroxyapatite (HA) with 5%, 10% or 20% wt. CONTENT: The scaffolds were fabricated in a cellular lattice structure (i.e. meshing mode) using a 0/90° lay down pattern with a continuous contour filament in order to achieve interconnected porous reticular structures. We varied the temperature, as well as injection speed and pressure during the bioplotting process to achieve scaffolds with pore size ranging between 200 and 400µm and adequate mechanical stability. The resulting scaffolds had an average pore size of 323µm and an average porosity of 32%. Characterization through ATR-FTIR revealed the presence of the characteristic bands of hydroxyapatite in the PCL matrix, and presented an increase of the intensity of the phosphate and carbonyl bands as the ceramic content increased. The bioplotted 3D scaffolds have a Young's modulus (E) in the range between 0.121 and 0.171GPa, which is compatible with the modulus of natural bone. PCL/NKB scaffolds, particularly 10NKBP (10% NKB wt.) exhibited the highest proliferation optical density, demonstrating an evident osteoconductive effect when cultured in Dulbecco's Modified Eagle Medium (DMEM). Scanning electron microscopy (SEM) confirmed osteoblast anchorage to all composite scaffolds, but a low adhesion to the all-PCL scaffold, as well as cell proliferation. The results from this study demonstrate the potential of PCL/NKB 3D bioplotted scaffolds as viable platforms to enable osseous tissue formation, which can be used in several tissue engineering applications, including improvement of bone tissue regeneration.

Trypsin as enhancement in cyclical tracheal decellularization: Morphological and biophysical characterization.

There are different types of tracheal disorders (e.g. cancer, stenosis and fractures). These can cause respiratory failure and lead to death of patients. Several attempts have been made for trachea replacement in order to restore the airway, including anastomosis and implants made from synthetic or natural materials. Tracheal allotransplantation has shown high rejection rates, and decellularization has emerged as a possible solution. Decellularization involves the removal of antigens from cells in the organ or tissue, leaving a matrix that can be used as 3D cell-scaffold. Although this process has been used for tracheal replacement, it usually takes at least two months and time is critical for patients with tracheal disorders. Therefore, there is necessary to develop a tracheal replacement process, which is not only effective, but also quick to prepare. The aim of this research was to develop a faster trachea decellularization protocol using Trypsin enzyme and Ethylenediaminetetraacetic acid (EDTA) as decellularization agents. Three protocols of cyclic trachea decellularization (Protocols A, B, and C) were compared. Following Protocol A (previously described in the literature), 15 consecutive cycles were performed over 32 days. Protocol B (a variation of Protocol A) ­ EDTA being added ­ with 15 consecutive cycles performed over 60 days. Finally, Protocol C, with the addition of Trypsin as a decellularization agent, 5 consecutive cycles being performed over 10 days. For the three protocols, hematoxylin­eosin (H&E) staining and DNA residual content quantification were performed to establish the effectiveness of the decellularization process. Scanning Electron Microscopy (SEM) was used to observe the changes in porosity and microarrays. To evaluate the structural matrices integrity, Thermogravimetric Analysis (TGA) and biomechanical test were used. None of the protocols showed significant alteration or degradation in the components of the extracellular matrix (ECM). However, in Protocol C, more cellular components were removed in less time, making it the most efficient process. In addition, the cell tracking and viability was evaluated with chondrocytes seeding on the scaffold obtained by Protocol C, which showed an adequate cell scaffolding ability of this matrix.