Biocompatibility

"La celulosa bacteriana es un polímero obtenido por fermentación con microrganismos de los géneros Acetobacter, Rhizobium, Agrobacterium y Sarcina, delas cuales la especie más eficiente es la Acetobacter Xylinum. Este polímero presenta la misma estructura química de la celulosa de origen vegetal, pero difiere en su conformación y propiedades fisicoquímicas, lo que lo hace atractivo para diversas aplicaciones, especialmente en las áreas de alimentos, procesos de separación, catálisis y en medicina, gracias a su biocompatibilidad. Sin embargo, el principal problema es la producción a gran escala limitada por los bajos rendimientos, lo que genera la necesidad de desarrollar alternativas que permitan disminuir o eliminar las causas de esta limitación. En este artículo se hace una revisión acerca de la síntesis, producción, propiedades y principales aplicaciones de la celulosa bacteriana, así como de algunas alternativas estudiadas para disminuir los inconvenientes en el escalamiento del proceso"

Functionally graded material (FGM) is a heterogeneous composite material including a number of constituents that exhibit a compositional gradient from one surface of the material to the other subsequently, resulting in a material with continuously varying properties in the thickness direction. FGMs are gaining attention for biomedical applications, especially for implants, owing to their reported superior composition. Dental implants can be functionally graded to create an optimized mechanical behavior and achieve the intended biocompatibility and osseointegration improvement. This review presents a comprehensive summary of biomaterials and manufacturing techniques researchers employ throughout the world. Generally, FGM and FGM porous biomaterials are more difficult to fabricate than uniform or homogenous biomaterials. Therefore, our discussion is intended to give the readers about successful and obstacles fabrication of FGM and porous FGM in dental implants that will bring state-of-the-art technology to the bedside and develop quality of life and present standards of care. V C 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A:

Lung Cancer has become one of the major diseases and causes a high mortality rate. Tumor growth is one of the major problems of it. It can be cured through various medicating practices such as Chemotherapy, radiation therapy, surgical stenosis, or combining the methods of practice. Several complications arising from tumors, injuries, and prolonged intubation can obstruct the tracheobronchial branch. To relieve from frequent suffocation, implants named tracheobronchial stents are used. Commercially available stents are not customizable based on a patient's anatomy, and biodegradable materials are not mechanically strong. The method described in this paper presents a novel biocompatible implant design, manufacturing, and performance testing methodologies. Various biodegradable Magnesium alloys are considered to design and analyze the mechanical effects on the tracheobronchial stent and effects of alloying components.. The predicted results can be expected for the AZ31B Magnesium alloy to have a tensile strength of 260MPa and a biodegradability period of 3.41 years when compared to other Mg alloys considered. Various Magnesium alloys can also be used to manufacture the biodegradable stent based on the requirement of the mechanical strength and biodegradability of the tumor to be cured in the lung passage.

The versatility of porous silicon (pSi), due to the myriad of possible
structures, ease of chemical modification and inherent biocompatibility, has resulted in it being readily tailored for numerous biomedical applications. Commonly prepared
via the anodisation of crystalline silicon wafers in HF electrolyte, pSi can be produced as films, microparticles, nanoparticles and free-standing membranes. The combination of both its unique physical properties and the incorporation of stable
surface functionalities have been fundamental to its performance. Through an immense number of modification techniques, numerous species from antibodies to
polymers can be integrated into pSi structures. This adaptability has produced materials with an increased half-life both in vitro and in vivo and enabled the development of both targeted detection platforms and local delivery of therapeutic
payloads. As a result, modified pSi has been readily applied to a range of biomedical applications including molecular detection, drug delivery, cancer therapy, imaging and tissue engineering.

The analysis of nanomechanical properties of the materials for biological applications has become an increasingly
useful tool on investigation of these materials. Although the biocompatibility of Ti has been
confirmed, it is difficult to meet all the requirements, such as antibacterial ability, osseointegration and mechanical
properties. Titanium alloys have a high friction coefficient while interacting with bone or tissue, which can cause wear
debris pain and loosening of implants.This situation could be avoided using alloy surface modification by a durable,
mechanically stable, wear resistant (TiAlV)N coating with a low friction coefficient as a base for an overlaying nanostructured
ТiOх.
This article represents the research on the influence of the process of vacuum arc deposition of (TiAlV)N coatings and
next vacuum oxidation on their mechanical properties and morphology. The microstructure, mechanical properties and
applicability of the investigated (Ti,Al,V)N/TiOx coatings for biocompatible titanium implants are discussed.

Stimuli-responsive bacterial cellulose-g-poly(acrylic acid) hydrogels were investigated for their potential use as an oral delivery system for proteins. These hydrogels were synthesized using electron beam irradiation without any cross-linking agents, thereby eliminating any potential toxic effects associated with cross-linkers. Bovine serum albumin (BSA), a model protein drug, was loaded into the hydrogels, and the release profile in simulated gastrointestinal fluids was investigated. Cumulative release of less than 10% in simulated gastric fluid (SGF) demonstrated the potential of these hydrogels to protect BSA from the acidic environment of the stomach. Subsequent conformational stability analyses of released BSA by SDS-PAGE, circular dichroism, and an esterase activity assay indicated that the structural integrity and bioactivity of BSA was maintained and preserved by the hydrogels. Furthermore, an increase in BSA penetration across intestinal mucosa tissue was observed in an ex vivo penetration experiment. Our fabricated hydrogels exhibited excellent cytocompatibility and showed no sign of toxicity, indicating the safety of these hydrogels for in vivo applications

The aim of this study was to compare the biocompatibility of two new calcium phosphate-based root canal sealers (CPC-I, CPC-II) with a commercially available zinc oxide eugenol based-sealer [Pulp canal sealer EWT (PCS EWT)] and Sealapex after implantation in the subcutaneous tissue of rats. Sterile polyethylene tubes were filled with the test materials. The tubes were implanted in the dorsum of male rats and after 1, 2, 4 and 8 weeks, the animals were killed, obtaining 5 specimens for each sealer. Empty tubes were used as negative control. Presence of inflammation, predominant cell types, and thickness of fibrous connective tissue adjacent to each inserted sample were recorded. At week 1, all sealers caused similar inflammatory reactions in the connective tissue of the animals, with most specimens presenting a moderate to intense chronic inflammatory reaction. After 2 weeks, CPC-II and (PCS EWT) showed a severe inflammatory reaction with presence of acute inflammatory cells, while CPC-I and Sealapex induced mild and moderate inflammatory reactions respectively. After 4 weeks, connective tissue in contact with CPC-I and Sealapex was more organized, while the tissue close to CPC-II and (PCS EWT) showed a moderate inflammatory reaction and had similar results to each other. After 8 weeks, mild inflammatory reactions were observed for CPC-I, (PCS EWT), and Seal apex. CPC-I induced the lowest inflammatory response at all evaluation periods, only CPC-II did not show a decrease in the inflammatory reaction over time. CPC-I sealer can be assigned a favorable biocompatibility level based on the study's histological findings.

This study aimed to evaluate in vitro biocompatibility of a composite of nanoscale biphasic calcium phosphate (BCP) and collagen (C) compared to pure BCP (P) in different composition ratios of nanohydroxyapatite to nano-β-tricalcium phosphate (HA/β-TCP). Each study group comprised of three ratios of BCP (30/70, 40/60, and 50/50). For evaluation of cellular response toward each ratio, mouse osteoblast (MC3T3-E1) cell line was cultivated on the scaffolds for 19 days. Analysis of cell proliferation, cell viability, cell attachment and morphology, alkaline phosphatase (ALP) activity, and osteocalcin synthesis were done on culture days 1, 3, 7, 13, 15, and 19, appropriately. The scanning electron microscopy showed that the osteoblasts attached successfully to scaffolds surfaces in both BCP groups and in all different ratios by spreading their filopodia and expressing similar viability that was confirmed by confocal laser scanning electron microscope. BCP scaffold (P3070) showed remarkable ALP activity, whereas BCP (P5050) showed highest osteocalcin activity. Collagen coating supported high cell proliferation on culture day 1 and possessed limited benefit restricted to early phase of cell differentiation. In conclusion, the fabricated nanoscale BCP scaffolds offered high biocompatibility and supported well the cell proliferation and differentiation regardless the composition ratio. Furthermore, higher ratio of TCP supported the early phase of cell proliferation, whereas higher HA ratio influenced the later phase. Finally, BCP scaffolds P5050 and C4060 were suggested as candidates for clinical applications.

Objective: The objective of this study was to evaluate the biocompatibility of five commercially available orthodontic miniscrews/ temporary anchorage devices. Materials and Methods: A cell culture system using commercially available human gingival fibroblasts was utilized. Miniscrews/ temporary anchorage devices obtained from Ormco, Ortho Organizer, 3M Unitek, American Orthodontics, and Rocky Mountain Orthodontics were immersed in culture medium for either 48 hours or two weeks. The surface area to volume character of the eluates produced by this method was within the suggested ISO range. Gingival fibroblasts were exposed to miniscrew/temporary anchorage device conditioned culture medium for 24 hours. Biocompatibility and cytotoxicity were measured using colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Results were analyzed using ANOVA with Tukey's post-test and P < 0.05). Results: LDH analysis showed no differences in disruption of cell membrane integrity, suggesting that the miniscrews/temporary anchorage devices were not cytotoxic to gingival fibroblasts (P > 0.05 for all comparisons). MTT analysis, used to quantify viable cells, demonstrated that 48 hour conditioned medium significantly affected cell viability (P < 0.001 for all treatments compared to control). In contrast two week conditioned medium from all five devices did not affect cell viability compared to control. Conclusion: The results of this study suggest that miniscrews/ temporary anchorage devices demonstrate longer-term biocompatibility with gingival fibroblasts and that the composition of the devices is not cytotoxic to oral cells. The general lack of data regarding the cytotoxicity of miniscrews/temporary anchorage devices in orthodontic treatment warrants further investigation.

Introduction: The aim of the present study was to evaluate the biocompatibility of two modified formulations of Portland cement (PC) mixed with either titanium oxide or both titanium oxide and calcium chloride. Methods and Materials: Polyethylene tubes were filled with modified PCs or Angelus MTA as the control; the tubes were then implanted in 28 Wistar rats subcutaneously. One tube was left empty as a negative control in each rat. Histologic samples were taken after 7, 15, 30 and 60 days. Sections were assessed histologically for inflammatory responses and presence of fibrous capsule and granulation tissue formation. Data were analyzed using the Fisher’s exact and Kruskal-Wallis tests. Result: PC mixed with titanium oxide showed the highest mean scores of inflammation compared with others. There was no statistically significant difference in the mean inflammatory grades between all groups in each of the understudy time intervals. Conclusion: The results showed favorable biocompatibility of these modified PC mixed with calcium chloride and titanium oxide.

Objectives: The aim of this study was to investigate, by means of radiological and histomorphometric analysis, the effect of resorbable collagen membranes on critical size defects (CSD) in rabbit tibiae filled with biphasic calcium phosphate. Materials and methods: Three CSD of 6 mm diameter were created in both tibiae of 20 New Zealand rabbits and divided into three groups according to the filling material: Group A (Ossceram), Group B (Ossceram plus Alveoprotect membrane), and Group C (unfilled control group). Five animals from each group were sacrificed after 15, 30, 45, and 60 days. Anteroposterior and lateral radiographs were taken. Samples were processed for observation under light microscopy. Results: At the end of treatment, radiological analysis found that cortical defect closure was greater in Group B than Group A, and radiopacity was clearly lower and more heterogeneous in the Group A cortical defects than in Group B. There was no cortical defect closure in Group C. Histomorphometric evaluation showed significant differences in newly formed bone and cortical closure in Group B compared with Groups A and C, with the presence of higher density newly formed bone in cortical and medullar zones. There was no cortical defect closure or medullar bone formation in Group C. Conclusions: Biphasic calcium phosphate functioned well as a scaffolding material allowing mineralized tissue formation. Furthermore, the addiction of absorbable collagen membranes enhanced bone gain compared with non-membrane-treated sites.

Porous TiNi alloys fabricated by self-propagating high-temperature synthesis (SHS) are biomaterials designed for medical application in substituting tissue lesions and they were clinically deployed more than 30 years ago. The SHS process, as a very fast and economically justified route of powder metallurgy, has distinctive features which impart special attributes to the resultant implant, facilitating its integration in terms of bio-mechanical/chemical compatibility. On the phenomenological level, the fact of high biocompatibility of porous SHS TiNi (PTN) material in vivo has been recognized and is not in dispute presently, but the rationale is somewhat disputable. The features of the SHS TiNi process led to a multifarious intermetallic Ti 4 Ni 2 (O,N,C)-based constituents in the amorphous-nanocrystalline superficial layer which entirely conceals the matrix and enhances the corrosion resistance of the unwrought alloy. In the current article, we briefly explore issues of the high biocompatibility level on which additional studies could be carried out, as well as recent progress and key fields of clinical application, yet allowing innovative solutions.

— We have investigated the stability of key electro-optical properties (Conductivity, Work Function, Transmittance) of several commonly used electrode materials for organic optoelectronics (Indium-Tin Oxide, Gold, Silver, Aluminum) in different media (Air, DI water, Phosphate Buffered Saline and Dulbecco's Modified Eagle Medium). By comparing the electrode materials side by side, we aimed to identify their advantages and drawbacks for use in solid/liquid devices. Since many applications of such devices involve the direct contact with biological species, we also investigated their biocompatibility by evaluating cytotoxicity of HEK293 cells cultured on the candidate materials.

This research aimed to evaluate the toxic effect of multi-walled carbon nanotubes (MW-CNTs) on yeast cells in order to apply MW-CNTs for possible improvement of the efficiency of microbial biofuel cells. The SEM and XRD analysis suggested that here used MW-CNTs are in the range of 10-25 nm in diameter and their structure was confirmed by Raman spectroscopy. In this study, we evaluated the viability of the yeast Saccharomyces cerevisiae cells, affected by MW-CNTs, by cell count, culture optical density and atomic force microscopy. The yeast cells were exposed towards MW-CNTs (of 2, 50, 100 μg/mL concentrations in water-based solution) for 24 h. A mathematical model was applied for the evaluation of relative growth and relative death rates of yeast cells. We calculated that both of the rates are two times higher in the case if yeasts were treated by 50, 100 μg/mL of MW-CNTs containing solution, comparing to that treated by 0 and 2 μg/mL c of MW-CNTs containing solution. It was determined that the MW-CNTs have some observable effect upon the incubation of the yeast cells. The viability of yeast has decreased together with MW-CNTs concentration only after 5 h of the treatment. Therefore, we predict that the MW-CNTs can be applied for the modification of yeast cells in order to improve electrical charge transfer through the yeast cell membrane and/or the cell wall.

Microfluidics is a science branch that investigates liquid behavior in ultra-small volumes (from micro- to femtolitres)
and liquid interaction with various micro- and nanostructures. Achievements in this field pave the way for creation
of great number of sophisticated microstructures that, combined with other components, could become independent multifunctional
device also known as lab-on-chip (LOC) [1]. However, advancements of microfluidics greatly depend on
what kind of structures can be created for liquid guidance and interactions in aforementioned scale. Requirements for
these structures sometimes might be relatively contradictive: for example, channel system needed for experiments might
be millimetres or even centimetres in overall size, but with micrometre sized channels or other features of this scale. Also,
in order for structures like these to become widely used they have to be cheap and easy to produce in huge quantities. This
puts most fabrication technologies to their limit and makes microfluidic research difficult and costly.
The goal of this work was to show possibility to produce microfluidical millimetre-sized components with integrated
functional microelements combining fused filament fabrication 3D printing (3DP) [2] and direct laser writing (DLW)
using femtosecond laser [3]. In this case, 3DP guarantees rapid and cheap fabrication of microchannels with size of
hundreds of micrometres inside a structure that has overall dimensions in range from millimetres to centimetres. DLW,
on the other hand, allows integrating intricate 3D microstructures into channels produced with 3DP. Structure fabrication
utilizing only 3DP or DLW would lead to either insufficient spatial resolution if only 3DP is used or costly and long
fabrication process if all structure is formed only with DLW.
Results of this work include demonstration what types of channels could be produced using commercially available
3D printer Ultimaker original and polylactic acid (PLA) as main material for channel fabrication [4]. Channel characteristics,
best fabrication parameters and arising problems are addressed. In case of DLW, we show fabrication of various
microfilters. These components, when integrated in 3DP fabricated channels, could act as passive particle sorters [Fig. 1
(a)]. Filter geometry best suited for integration using DLW as well as filtering is discussed. Finally, novel method for
sealing PLA channels with glass covers without using any additional glue is proposed and tested.

The aim of this study was to find out the in-vivo radiography density changes of
hydroxyapatite coated porous tantalum biomaterial implant after surgical implantation in rats. Ten
adult male Sprague Dawley rats were divided into two groups: hydroxyapatite-coated porous
tantalum (pTa-HAp) and uncoated porous tantalum (pTa). The implants with dimension of 5 x 2 x 0.5
mm3 was inserted into flatten bone defects drilled at the femur bone on latero-medial region. The
implant density from right lateral view radiogram was analyzed at day 0, 7, 14 and 30
post-implantation. The results showed that the radiodensity of both pTa and pTa-HAp groups
decreased in time of implantation. The radiodensity changes of pTa-HAp showed higher decrease
compared to pTa.

Gold nanoparticles (Au NPs) have been tested as targeted delivery agents because of their high chemical stability and surface plasmon properties. Here, we investigated the biocompatibility of Au spheres (5-, 10-, 20-, 30-, 50-. and 100-nm), cubes (50-nm), and rods (10 × 90 nm) on a retinal pigment epithelial (ARPE-19) cell line. The lethal dose for killing 50% of the cells (LD 50) was evaluated using an MTT (3-[4, 5 dimethyl-thiazoly-2-yl] 2-5 diphenyl tetrazolium bromide) assay. At and above LD 50 , based on mass concentrations, the confluent cell layer began to detach, as shown by real-time measurements of electric impedance. We found that the biocompat-ibility of spheres improved with increasing nanoparticle size. The Au rods were less biocompatible than 10-nm spheres. Confocal microscopy showed that cubic (50-nm) and spherical NPs (50-and 100-nm) neither had cyto-toxic effects nor entered cells. Lethal doses for internalized spherical NPs, which were toxic, were recalculated based on surface area (LD 50,A) concentrations. Indeed, when biocompatibility was expressed as the surface area concentration of NPs, the curve was independent of size. The LD 50,A of Au nanospheres was 23 cm 2 /ml. Our findings demonstrate that the sole modulation of the surface area would make it possible to use Au NPs for therapeutic purposes.

Objective: Resin cements, regardless of their biocompatibility, have been widely used in restorative dentistry during the recent years. These cements contain hydroxy ethyl methacrylate (HEMA) molecules which are claimed to penetrate into dentinal tubules and may affect dental pulp. Since tooth preparation for metal ceramic restorations involves a large surface of the tooth, cytotoxicity of these cements would be more important in fixed prosthodontic treatments. The purpose of this study was to compare the cytotoxicity of two resin cements (Panavia F2 and Rely X Plus) versus zinc phosphate cement (Harvard) using rat L929-fibroblasts in vitro. Materials and Methods: In this experimental study, ninety hollow glass cylinders (internal diameter 5-mm, height 2-mm) were made and divided into three groups. Each group was filled with one of three experimental cements; Harvard Zinc Phosphate cement, Panavia F2 resin cement and Rely X Plus resin cement. L929-Fibroblast were passaged and subsequently cultured in 6-well plates of 5×10 5 cells each. The culture medium was RPMI_ 1640. All samples were incubated in CO 2 . Using enzyme-linked immune-sorbent assay (ELISA) and (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) (MTT) assay, the cytotoxicity of the cements was investigated at 1 hour, 24 hours and one week post exposure. Statistical analyses were performed via two-way ANOVA and honestly significant difference (HSD) Tukey tests. Results: This study revealed significant differences between the three cements at the different time intervals. Harvard cement displayed the greatest cytotoxicity at all three intervals. After 1 hour Panavia F2 showed the next greatest cytotoxicity, but after 24-hours and oneweek intervals Rely X Plus showed the next greatest cytotoxicity. The results further showed that cytotoxicity decreased significantly in the Panavia F2 group with time (p<0.005), cytotoxicity increased significantly in the Rely X Plus group with time (p<0.001), and the Harvard cement group failed to showed no noticeable change in cytotoxicity with time. Conclusion: Although this study has limitations, it provides evidence that Harvard zinc phosphate cement is the most cytotoxic product and Panavia F2 appears to be the least cytotoxic cement over time.