On the synergistic effect of sulfonic functionalization and acidic adhesive conditioning to enhance the adhesion of PEEK to resin-matrix composites.

OBJECTIVE: The objective of this study was to evaluate the combined effect of the sulfuric acid etching and an acidic adhesive conditioning on the shear bond strength of PEEK to a resin-matrix composite. MATERIALS AND METHODS: Forty PEEK specimens were assigned randomly to 4 groups for H2SO4 etching followed by universal adhesive (pH at 2.5) conditioning for 0, 1, 3, and 5 min. Thirty PEEK specimens were divided into 3 groups for only acidic adhesive conditioning for 0, 1, 3, and 5 min. After the light-curing of the adhesive, a nanohybrid resin composite was applied onto the surfaces and then light-cured following the manufacturer`s guidelines. All specimens were stored in distilled water at 37 °C for 24 h mechanical testing. Shear bond strength tests were performed using a universal testing machine. Surfaces were analyzed by SEM, light interferometry, FTIR, and liquid contact angle measurement. Statistical analysis was performed by one-way ANOVA and Tukey's post hoc tests (p < 0.05). RESULTS: No adhesion was achieved between untreated PEEK a resin-matrix composite, regardless of the adhesive conditioning time points. Shear bond strength of H2SO4-etched PEEK to resin-matrix composite increased with time (0 mmin. 4.95 ± 2.86 MPa < 1 min: 9.35 ± 2.26 MPa < 3 min: 17.84 ± 2.82 MPa < 5 min: 21.43 ± 5.00 MPa). SEM images revealed a significant modification of PEEK surface topography after the H2SO4 etching. SIGNIFICANCE: The acidic adhesive was unable to modify the untreated PEEK surface to establish an effective adhesion although a synergistic effect was noticed when the universal (acidic) adhesive was applied over a H2SO4-etched PEEK surface, thus improving the PEEK to resin-matrix composite adhesion.

Biofilm behavior on sulfonated poly(ether-ether-ketone) (sPEEK).

Poly(ether-ether-ketone) (PEEK) has also shown to be very attractive for incorporating therapeutic compounds thanks to a sulfonation process which modifies the material structure resulting in a sulfonated-PEEK (sPEEK). Concerning biomedical applications, the objective of this work was to evaluate the influence of different sulfonation degree of sPEEK on the biofilm growth. PEEK samples were functionalized by using sulphuric acid (98%) and then dissolved into dimethyl-sulfoxide. A dip coating technique was used to synthesize sPEEK thin films. The sulfonation degree of the materials was analyzed by FT-IR, H NMR, TG and IEC. The surfaces were characterized by scanning electron microscopy, profilometry and contact angle analyses. Subsequently, the biofilm formation on sulfonated-PEEK based on Streptococcus mutans and Enterococcus faecalis was measured by spectrophotometry, colony forming units (CFUmL-1) and SEM. Results obtained from thermal and chemical analyses showed an intensification in sulfonation degree for sPEEK at 2 and 2.5h. The E. faecalis or S. mutans biofilm growth revealed statistically significant differences (p<0.05) between 2 and 3h sulfonation groups. A significant decrease (p<0.05) in CFUmL-1 was recorded for S. mutans or E. faecalis biofilm grown on 2.5 or 3h sPEEK. Regarding the thermal-chemical and microbiologic analyses, the sulfonation degree of sPEEK ranging from 2 up to 3h was successful capable to decrease the biofilm growth. That revealed an alternative strategy to embed anti-biofilm and therapeutic compounds into PEEK avoiding infections in biomedical applications.

Chemical, microscopic, and microbiological analysis of a functionalized poly-ether-ether-ketone-embedding antibiofilm compounds.

Poly-ether-ether-ketone (PEEK) is currently introduced as an alternative material for orthopedic implants due to its biocompatibility and low elastic modulus compared to titanium. Also, a sulphonation treatment can functionalize PEEK to embed therapeutical substances. The objective of this work was to functionalize a PEEK film to incorporate novel lactam-based antibiofilms compounds. PEEK samples were functionalized by sulphuric acid treatment and then dissolved in dimethylsulfoxide, where lactams were added to be incorporated into the polymer. A dip-coating technique was used to synthesize a thin film on a glass-based substrate. The degree of sulfonation (DS) and the incorporation of lactams into sulphonated PEEK (sPEEK) were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis (TGA), and scanning electron microscopy. A DS of 65% was obtained and TGA curves confirmed the presence of SO3 H and lactams in the sPEEK structure. The growth of Streptococcus mutans biofilm decreased on sPEEK surface containing lactams when compared to sPEEK free of lactams. That indicated the antibiofilm activity of those compounds was maintained after incorporation into sPEEK. Planktonic growth analysis showed no long distant effects of sPEEK containing lactams, indicating that no systemic effects should be expected upon clinical uses of medical devices produced with lactam-treated sPEEK. Results revealed that inclusion of lactams into sPEEK represents a good alternative for the production of biomaterials resistant to bacterial accumulation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 3015-3020, 2016.

Structure and properties of polypyrrole/bacterial cellulose nanocomposites.

An electrically conducting composite based on bacterial cellulose (BC) and polypyrrole (PPy) was prepared through in situ oxidative polymerization of pyrrole (Py) in the presence of BC membrane using ammonium persulfate (APS), as an oxidant. The electrical conductivity, morphology, mechanical properties and thermal stability of the composites obtained using APS (BC/PPy·APS) were evaluated and compared with BC/PPy composites prepared using as oxidant agent Iron III chloride hexahydrate (FeCl3·6H2O). The morphology of the BC/PPy·APS composites is characterized by spherical conducting nanoparticles uniformly distributed on the BC nanofiber surface, while the composites produced with FeCl3·6H2O (BC/PPy·FeCl3) is composed of a continuous conducting polymer layer coating the BC-nanofibers. The electrical conductivity of BC/PPy·FeCl3 was 100-fold higher than that found for BC/PPy·APS composites. In order to understand the site-specific interaction between PPy and BC functional groups, both composites were characterized by Fourier transform infrared (attenuated total reflectance mode) spectroscopy attenuation reflectance (FTIR-ATR) and X-ray photoelectron spectrometry (XPS). The affinity between functional groups of PPy·FeCl3 and BC is higher than that found for BC/PPy·APS composite. In addition, the tensile properties were also influenced by the chemical affinity of both components in the polymer composites.