Mechanical properties, in vitro and in vivo biocompatibility analysis of pure iron porous implant produced by metal injection molding: A new eco-friendly feedstock from natural rubber (Hevea brasiliensis).

Metal injection molding (MIM) has become an important manufacturing technology for biodegradable medical devices. As a biodegradable metal, pure iron is a promising biomaterial due to its mechanical properties and biocompatibility. In light of this, we performed the first study that manufactured and evaluated the in vitro and in vivo biocompatibility of samples of iron porous implants produced by MIM with a new eco-friendly feedstock from natural rubber (Hevea brasiliensis), a promisor binder that provides elastic property in the green parts. The iron samples were submitted to tests to determine density, microhardness, hardness, yield strength, and stretching. The biocompatibility of the samples was studied in vitro with adipose-derived mesenchymal stromal cells (ADSCs) and erythrocytes, and in vivo on a preclinical model with Wistar rats, testing the iron samples after subcutaneous implant. Results showed that the manufactured samples have adequate physical, and mechanical characteristics to biomedical devices and they are cytocompatible with ADSCs, hemocompatible and biocompatible with Wistars rats. Therefore, pure iron produced by MIM can be considered a promising material for biomedical applications.

In situ drug release measuring in α-TCP cement by electrochemical impedance spectroscopy.

The use of drug delivery systems is a good technique to leave the right quantity of medicine in the patient's body in a suitable dose, because the drug application is delivered directly to the affected region. The current techniques such as HPLC and UV-Vis for the drug delivery calculation has some disadvantages, as the accuracy and the loss of the sample after characterization. With the aim of reducing the amount of material used during the characterization and have a non-destructive test with instantaneous results, the present paper shows the possibility of using electrochemical impedance spectroscopy (EIS) to have a drug delivery measurement during the release phenomena for a calcium phosphate cement (CFC) delivery system with gentamicin sulfate (GS) and lidocaine hydrochloride (LH), at a ratio of 1% and 2%, respectively. The equivalent circuit and the chemical mechanism involved during the measurements have been proposed as a tool to determine the drug delivery profile. The method has been compared with the UV-Vis technique. XRD was realized to verify conditions, before and after release. It was possible to verify the potential for using EIS as an instant technique to quantify drug delivery.

Tissue-engineered solution containing cells and biomaterials-an in vitro study: A perspective as a novel therapeutic application.

Some biomaterial scaffolds can positively interfere with tissue regeneration and are being developed to successfully repair the tissue function. The possibility of using epithelial cells combined with biomaterials appears to be a new option as therapeutic application. This combination emerges as a possibility for patients with Mayer-Rokitansky-Kuster-Hauser syndrome which requires vaginal repair and can be performed with tissue-engineered solution containing cells and biomaterials. It is expected that tissue-engineered solution containing cells and biomaterials would promote tissue repair in a more efficient, modern, and safe way. This study tested the efficiency of tissue-engineered solution containing human malignant melanoma cell line (HMV-II) and different biomaterials, including Cellprene®, Membracel®, and poly lactic-co-glycolic acid/epoxidized polyisoprene. The cells adhered better on poly lactic-co-glycolic acid/epoxidized polyisoprene, and it was found that tissue-engineered solution may also contain mesenchymal stem cells cultivated on poly lactic-co-glycolic acid/epoxidized polyisoprene. Histological, immunofluorescence, and scanning electron microscopy analyses were performed. These initial in vitro results suggest that tissue-engineered solution containing cells and poly lactic-co-glycolic acid/epoxidized polyisoprene is a potential for tissue reconstruction.

Fiber-reinforced silicone for tracheobronchial stents: An experimental study.

A trachea is a tubular structure composed of smooth muscle that is reinforced with cartilage rings. Some diseases can cause sagging in smooth muscle and cartilaginous tissue. The end result is reduction (narrowing) of the trachea diameter. A solution to this problem is the use of tracheal stents, which are small tubular devices made of silicone. One is inserted into the trachea to prevent or correct its constriction. The purpose of tracheal stent use is to maintain cartilage support that would otherwise be lost in the airway. Current tracheal stent models present limitations in terms of shape and characteristics of the silicone used in their production. One of the most important is the large thickness of the wall, which makes its placement difficult; this mainly applies to pediatric patients. The wall thickness of the stent is closely related to the mechanical properties of the material. This study aims to test the reinforcement of silicone with three kinds of fibers, and then stents that were produced using fiber with the best compressive strength characteristics. Silicone samples were reinforced with polypropylene (PP), polyamide (PA), and carbon fiber (CF) at concentrations of 2% and 4% (vol%), which then underwent tensile strength and Shore A hardness testing. Samples with fiber showed good characteristics; surface analyses were carried out and they were used to produce stents with an internal diameter of 11 or 13mm and a length of 50mm. Stents underwent compression tests for qualitative evaluation. Samples with 2% and 4% CF blends showed the best mechanical performance, and they were used to produce stents. These samples presented similar compressive strengths at low deformation, but stents with a 4% CF blend exhibited improved compressive strength at deformations greater than 30-50% of their diameter (P ≤ 0.05). The addition of 2% and 4% CF blends conferred greater mechanical strength and resistance to the silicone matrix. This is particularly true at low deformation, which is the condition where the stent is used when implanted. In the finite element compression strength tests, the stent composite showed greater compression strength with the addition of fiber, and the results were in accordance with mechanical compression tests performed on the stents. In vivo tests showed that, after 30 days of post-implantation in sheep trachea, an inflammatory process occurred in the region of the trachea in contact with the stent composite and with the stent without fiber (WF). This response is a common process during the first few days of implantation.

Dimensional evaluation of patient-specific 3D printing using calcium phosphate cement for craniofacial bone reconstruction.

The 3D printing process is highlighted nowadays as a possibility to generate individual parts with complex geometries. Moreover, the development of 3D printing hardware, software and parameters permits the manufacture of parts that can be not only used as prototypes, but are also made from materials that are suitable for implantation. In this way, this study investigates the process involved in the production of patient-specific craniofacial implants using calcium phosphate cement, and its dimensional accuracy. The implants were previously generated in a computer-aided design environment based on the patient's tomographic data. The fabrication of the implants was carried out in a commercial 3D powder printing system using alfa-tricalcium phosphate powder and an aqueous solution of Na2HPO4 as a binder. The fit of the 3D printed implants was measured by three-dimensional laser scanning and by checking the right adjustment to the patient's anatomical biomodel. The printed parts presented a good degree of fitting and accuracy.