Synthesis, Characterization, Antibacterial Properties, and In Vitro Studies of Selenium and Strontium Co-Substituted Hydroxyapatite.

In this study, as a measure to enhance the antimicrobial activity of biomaterials, the selenium ions have been substituted into hydroxyapatite (HA) at different concentration levels. To balance the potential cytotoxic effects of selenite ions (SeO32-) in HA, strontium (Sr2+) was co-substituted at the same concentration. Selenium and strontium-substituted hydroxyapatites (Se-Sr-HA) at equal molar ratios of x Se/(Se + P) and x Sr/(Sr + Ca) at (x = 0, 0.01, 0.03, 0.05, 0.1, and 0.2) were synthesized via the wet precipitation route and sintered at 900 °C. The effect of the two-ion concentration on morphology, surface charge, composition, antibacterial ability, and cell viability were studied. X-ray diffraction verified the phase purity and confirmed the substitution of selenium and strontium ions. Acellular in vitro bioactivity tests revealed that Se-Sr-HA was highly bioactive compared to pure HA. Se-Sr-HA samples showed excellent antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus carnosus) bacterial strains. In vitro cell-material interaction, using human osteosarcoma cells MG-63 studied by WST-8 assay, showed that Se-HA has a cytotoxic effect; however, the co-substitution of strontium in Se-HA offsets the negative impact of selenium and enhanced the biological properties of HA. Hence, the prepared samples are a suitable choice for antibacterial coatings and bone filler applications.

Electrophoretic co-deposition of PEEK-hydroxyapatite composite coatings for biomedical applications.

This study focuses on the optimization of electrophoretic deposition (EPD) and suspension parameters for producing PEEK-hydroxyapatite (HA) coatings with feasible microstructure, adhesion strength, and in-vitro bioactivity. Nanostructured hydroxyapatite (HA) micro-granules were incorporated with PEEK to form PEEK-hydroxyapatite composite coatings via EPD. After EPD, a heat-treatment at 375 °C was applied for densification of the coatings and for enhancing the adhesion between the coatings and the substrates. It was found that both adhesion strength and in-vitro bioactivity of the coatings were dependent on the PEEK and HA relative contents. Thus, increasing the amount of HA improved the bioactivity while decreased the adhesion strength of the coatings. Apatite-like layer formation was observed on coatings with high HA content after incubation for three days in simulated body fluid (SBF). Finally, a deposition mechanism was proposed for the EPD of the PEEK-hydroxyapatite composite system.

Comparison of diagnostic yield of AFB with sputum induction to spontaneous sputum examination in suspected pulmonary tuberculosis.

OBJECTIVE: To compare the diagnostic yield of AFB positivity with sputum induction to spontaneous sputum examination in suspected cases of pulmonary tuberculosis. STUDY DESIGN: Comparative study. PLACE AND DURATION OF STUDY: Military Hospital, Rawalpindi, from January to December 2006. METHODOLOGY: Sputum specimens were collected by both techniques from 164 patients with clinical and radiological suspicion of pulmonary tuberculosis admitted in medical wards. All specimens were examined for AFB smear and culture positivity. Sputum induction was done for 15-20 minutes with 3% sterile hypertonic saline solution by nebulization in all cases. Proportions were compared using Chi-square test. RESULTS: Among 164 patients, 32 patients (19.5%) were not expectorating spontaneously. Sputum induction was successful in 22 (68.75%) cases and AFB smear was positive in 03 (9.37%) and AFB culture was positive in 7 (21.8%) of these cases. One hundred and thirty two (80.5%) patients were already expectorating and both Day-1 (spontaneous) and Day-2 (induced) sputum samples were available. Day-1 (spontaneous) sputum specimens revealed AFB smear positive results in 20 (15.15%) patients, and AFB culture positive results in 24 (18.18%) patients. Smear positivity on Day-2 (induced) sputum samples was 21.21% (28) with 27.27% (36) culture positivity. CONCLUSION: In expectorating patients, AFB smear and culture positivity results remain comparable with spontaneous and induced sputum sampling. Sputum induction improves the diagnostic yield for AFB in patients unable to expectorate adequate sputum sample.