Evaluation of Biocompatibility of PLA/PHB/TPS Polymer Scaffolds with Different Additives of ATBC and OLA Plasticizers.

One of the blends that is usable for 3D printing while not being toxic to cell cultures is the lactic acid (PLA)/polyhydroxybutyrate (PHB)/thermoplastic starch (TPS) blend. The addition of plasticizers can change the rate of biodegradation and the biological behavior of the material. In order to evaluate the potential of the PLA/PHB/TPS material in combination with additives (plasticizers: acetyl tributyl citrate (ATBC) and oligomeric lactic acid (OLA)), for use in the field of biomedical tissue engineering, we performed a comprehensive in vitro characterization of selected mixture materials. Three types of materials were tested: I: PLA/PHB/TPS + 25% OLA, II: PLA/PHB/TPS + 30% ATBC, and III: PLA/PHB/TPS + 30% OLA. The assessment of the biocompatibility of the materials included cytotoxicity tests, such as monitoring the viability, proliferation and morphology of cells and their deposition on the surface of the materials. The cell line 7F2 osteoblasts (Mus musculus) was used in the experiments. Based on the test results, the significant influence of plasticizers on the material was confirmed, with their specific proportions in the mixtures. PLA/PHB/TPS + 25% OLA was evaluated as the optimal material for biocompatibility with 7F2 osteoblasts. The tested biomaterials have the potential for further investigation with a possible change in the proportion of plasticizers, which can have a fundamental impact on their biological properties.

Biomechanical Testing of Two-Unit Bridges and a Comparison of Replacement Retention Depending on a Cementation Medium, Replacement Position, and Gap Size.

Dental replacements are placed between the abutment teeth. The exceptions are two-unit bridges, as they are supported by a single tooth prepared only on one side of the missing tooth. The presented study deals with an analysis of a pressure force action on two-unit bridges placed in the frontal part (20 samples), where the pressure action is lower, and in the distal part (20 samples), where the pressure action is higher. A CAD program by 3Shape was used for digital designing with two different gap settings, 10 µm (20 samples) and 30 µm (20 samples). Two-unit bridges were attached to the prepared tooth using two types of dental cement (20/20 samples), which were selected for their physical and bioactive properties. All two-unit bridges (a total of 80 samples) were fabricated from CoCr alloys on Mlab cusing R by applying the Selective Laser Melting (SLM) technology. Mechanical testing was performed using the Inspekt5 table blue. The obtained data were used to verify the hypotheses-a difference between both types of cement (A ≠ B), a difference between the frontal and distal two-unit bridges (F ≠ D) and a difference between the gap sizes (10 ≠ 30). To confirm the given theories, data were statistically evaluated using the F-test and subsequent t-tests. The resulting p-value was compared with the level of significance (α = 0.05). A statistical evaluation revealed a significant difference between the compared groups; however, no explicit correlation between the individual groups of specimens was identified.

Morphometric analysis - effect of the radiofrequency interface of electromagnetic field on the size of hatched Dermacentor reticulatus larvae.

INTRODUCTION AND OBJECTIVE: Electromagnetic radiation interactions with living systems have been one of determining factors in biological evolution. This study investigates the effect of 900 MHz radiofrequency (RF) electromagnetics field (EMF) exposure of eggs on the development of Dermacentor reticulatus larvae. The basic objective was to determine whether the 900 MHz RF-EMF has the potential to influence the size of the body of the hatched larvae of D. reticulatus ticks. MATERIAL AND METHODS: To this aim, eggs from 3 fully engorged females of D. reticulatus were included in the test procedure. Altogether four groups of eggs were designated which included eggs from each female. We used RF-EMF frequency of 900 MHz. Eggs were exposed to EMF for different time periods (30, 60 and 90 minutes) in dark, electromagnetically shielded anechoic chamber. After the irradiation eggs were allowed to hatch in climatic chamber. Randomly selected 200 larval individuals were measured to get basic morphological records. Four body traits including the total body length (TBL), length of gnathosoma with scutum (GSL), the total body width (TBW), and the width of basis capituli (BCW) were measured. RESULTS: The D. reticulatus larvae hatched from eggs exposed for 60 minutes, had demonstrably larger dimensions of all measured body traits not only as a control unexposed group but also as other experimental groups. CONCLUSIONS: The study shows, particularly, that artificial EMF that is used in smartphone technology impacts seriously D. reticulatus larvae development.

In Vitro Degradation of Specimens Produced from PLA/PHB by Additive Manufacturing in Simulated Conditions.

Biopolymers have been the most frequently studied class of materials due to their biodegradability, renewability, and sustainability. The main aim of the presented study was to evaluate degradability of the polymer material blend which was immersed in different solutions. The present study included the production of three different mixtures of polylactic acid and polyhydroxybutyrate, each with a different content of triacetin, which was used as a plasticiser. Applying 3D printing technology, two types of cylindrical specimen were produced, i.e., a solid and a porous specimen, and subjected to in vitro natural degradation. The biodegradation process ran for 195 days in three different solutions (saline, phosphate-buffered saline (PBS), and Hank's solution) in stable conditions of 37 °C and a pH of 7.4, while the specimens were kept in an orbital motion to simulate the flow of fluids. The goal was to identify the effects of a solution type, specimen shape and material composition on the biodegradation of the materials. The monitored parameters included changes in the solution quantity absorbed by the specimens; morphological changes in the specimen structure; and mechanical properties. They were measured by compressive testing using the Inspekt5 Table Blue testing device. The experiment revealed that specimen porosity affected the absorption of the solutions. The non-triacetin materials exhibited a higher mechanical resistance to compression than the materials containing a plasticiser. The final result of the experiment indicated that the plasticiser-free specimens exhibited higher values of solution absorption, no formation of block cracks or bubbles, and the pH values of the solutions in which these materials were immersed remained neutral for the entire experiment duration; furthermore, these materials did not reduce pH values down to the alkaline range, as was the case with the solutions with the plasticiser-containing materials. Generally, in applications where high mechanical resistance, earlier degradation, and more stable conditions are required, the use of non-plasticiser materials is recommended.

A comparison of experimental compressive axial loading testing with a numerical simulation of topologically optimized cervical implants made by selective laser melting.

In recent years, the number of cervical interventions has increased. The stress shielding effect is a serious complication in cervical spine interventions. Topological optimization is based on finite element method structural analysis and numerical simulations. The generated design of cervical implants is made from Ti6Al4V powder by selective laser melting while the optimized cage is numerically tested for compressive axial loading and the results are compared with experimental measurement. Additive manufacturing technologies and new software possibilities in the field of structural analysis, which use the finite element method tools, help to execute implant topological optimization that is useful for clinical practice. The inner structures of the implant would be impossible to make by conventional manufacturing technologies. The resulting implant design, after modification, must fulfill strict application criteria for the area of cervical spine with respect to its material and biomechanical properties. The aim of this work was to alter the mechanical properties of the cervical intervertebral cage to address the clinical concern of the stress shielding effect by topological optimization. A methodology of cervical implant compressive axial loading numerical simulation was created, and subsequent experimental testing was done to obtain real material properties after a selective laser melting process. The weight of the optimized implant was reduced by 28.92 %. Results of the experimental testing and numerical simulation of topologically optimized design showed 10-times lower stiffness compared to the solid cage design, and the real yield strength of the optimized structure is 843.8 MPa based on experimental results.

3D printed Polylactid Acid based porous scaffold for bone tissue engineering: an in vitro study.

PURPOSE: The objective of this study was to fabricate PLA-based porous scaffold by 3D printing technology and to evaluate their cytotoxicity and biocompatibility under in vitro conditions in respect to bone tissue engineering. MATERIAL AND METHODS: Pure PLA in filamentous form was processed via 3D printing technology of fused filament fabrication into porous scaffolds. The structure and porosity of scaffolds were measured by metrotomography. PLA scaffolds were pre-treated by human serum, foetal bovine serum and complete cell culture medium to enhance bio-attractivity of the scaffold's surface for the adherence of the cells. Cells were enzymatically isolated from the periosteum of the proximal tibia and then expanded in monolayer. Periosteum-derived osteoprogenitors (PDOs) were seeded on the pre-treated PLA scaffolds and subsequent cell proliferation was measured by commercially available cell proliferation assay. Adherence of PDOs on the PLA scaffold was confirmed by scanning electron microscopy (SEM). RESULTS: Prepared scaffolds had well-defined structure and were characterized by uniform distribution of pores. They were non-toxic and biocompatible with PDOs, however, PLA scaffold with the periosteum-derived progenitor cells was significantly better in the group of scaffolds pre-treated with normal human serum. CONCLUSIONS: The obtained PLA porous scaffolds favored attachment of periosteum derived progenitors and proliferation, furthermore, cells penetrated into the scaffold through the interstitial pores which was meaningful for cytocompatibility evaluation.