Silk fibroin/hydroxyapatite composite membranes: Production, characterization and toxicity evaluation.

Alloplastic materials based on biopolymers such as silk fibroin (SF) have provided the synthesis of excellent biomaterials for bone repair. The aim of the present study was to produce SF membranes associated to hydroxyapatite (HA) and evaluate their physicochemical characteristics and the toxicity potential. After obtaining the SF, the HPLC was executed to verify the elimitation of serecin, a toxic protein of the silk, and the cytotoxicity assay was assessed in the subtances from the SF processing. SF and SF-HA membranes were evaluated by SEM, EDS, FTIR, mechanical properties and toxicity (cytotoxicity, genotoxicity and mutagenic effects). The serecin was elimined in the SF process, and its cytotoxicity was confirmed. SF and SF-HA membranes presented interesting results based on the physicochemical characterization. SF membrane showed cytotoxic, genotoxic and mutagenic effects. In conclusion, SF and SF-HA membranes presented adequate mechanical resistance to act respectively as wound healing or bone filling materials, and they were hydrophilic. SF-HA membrane did not present any toxic potential and allowed cell adhesion and proliferation. The unexpected cyto/genotoxicity and mutagenic effect of SF evidenced the importance of investigating the toxic potential of biomaterials, mainly those in contact with human body for prolonged time.

Bacterial cellulose membrane functionalized with hydroxiapatite and anti-bone morphogenetic protein 2: A promising material for bone regeneration.

Bone tissue engineering seeks to adequately restore functions related to physical and biological properties, aiming at a repair process similar to natural bone. The use of compatible biopolymers, such as bacterial cellulose (BC), as well as having interesting mechanical characteristics, presents a slow in vivo degradation rate, and the ability to be chemically modified. To promote better bioactivity towards BC, we synthesized an innovative BC membrane associated to hydroxyapatite (HA) and anti-bone morphogenetic protein antibody (anti-BMP-2) (BC-HA-anti-BMP-2). We present the physical-chemical, biological and toxicological characterization of BC-HA-anti-BMP-2. Presence of BC and HA components in the membranes was confirmed by SEM-EDS and FTIR assays. No toxic potential was found in MC3T3-E1 cells by cytotoxicity assays (XTT Assay and Clonogenic Survival), genotoxicity (Comet Assay) and mutagenicity (Cytokinesis-blocked micronucleus Test). The in vitro release kinetics of anti-BMP-2 antibodies detected gradually reducing antibody levels, reducing approximately 70% in 7 days and 90% in 14 days. BC-HA-anti-BMP-2 increased SPP1, BGLAP, VEGF, ALPL, RUNX2 and TNFRSF11B expression, genes involved in bone repair and also increased mineralization nodules and phosphatase alcalin (ALP) activity levels. In conclusion, we developed BC-HA-anti-BMP-2 as an innovative and promising biomaterial with interesting physical-chemical and biological properties which may be a good alternative to treatment with commercial BMP-2 protein.

Toxicity of therapeutic contact lenses based on bacterial cellulose with coatings to provide transparency.

Therapeutic contact lenses were developed from bacterial cellulose (BC) by the Institute of Chemistry at Brazil's São Paulo State University (UNESP). In a previous study, cyclodextrins (CD) and medications such as ciprofloxacin (CP) and diclofenac sodium (DS) were incorporated into the lenses to provide therapeutic properties and control drug release. However, significant opacity was seen in the material inherent to cellulose. In order to achieve full material transparency, the lenses were coated with an organic-inorganic hybrid compound containing aluminum alkoxide and glycidoxypropyltrimethoxysilane (GPTS)(H), or chitosan (Q) nanoparticles. This study evaluated the toxicity of these contact lenses to ensure the safety of these materials for future availability to the medical device industry. Lenses composed of BC and coated with either GPTS (H) or chitosan (Q), incorporating ciclodextrin (CD) to release diclofenac sodium (DS) or ciprofloxacin (CP), were submitted to cytotoxicity assays (XTT and Clonogenic Survival), genotoxicity (Comet Assay) and mutagenicity (Cytokinesis-blocked micronucleus assay) directly in cell culture. Statistical analyses were performed using the Tukey and Dunnett or Kruskal-Wallis and Dunn tests. All of the nanoparticles used in the lense coatings did not show cytotoxic effects by the XTT test (p > 0.05; Dunnett). Only materials associated with diclofenac sodium (BC-H-CD-DS and BC-Q-CD-DS) presented significantly different survival fractions compared to negative control (p < 0.001; Dunnett). Genotoxicity evaluation revealed a genotoxic effect in BC-H-CD-DS (p < 0.05; Dunn). All tested lenses did not present any mutagenic effect. These results indicate that improvements in DS incorporation are needed to eliminate toxicity. We demonstrated promising results in the safety of employing BC lenses functionalized with a drug delivery system permitting the bioavailability of ophthalmic drugs. Further studies utilizing other specific tests, such as corneal lineage are required before safe and efficient ophthalmologic use.