A comparative study on fabrication techniques of gelable bone matrix derived from porcine tibia.

Recently, several types of native tissues have been enzymatically digested to prepare hydrogels that have natural-mimic extracellular matrix (ECM) proteins, architecture, and biologic activities. However, the residual detergents and salts remaining in the hydrogel may cause some undesirable effects on compatibility, functionality, and bioactivity of the material. In this study, we enzymatically digested the demineralized and decellularized bone matrix (DDBM) and adopted two common methods that included dialysis against distilled water and acetone precipitation for sample desalting. Efficiency in salt removal, protein preservation, gelation ability, and in vivo biocompatibility and function were compared to the DDBM digest without a desalting treatment. After lyophilization, the dialyzed, precipitated, and non-desalted DDBM digests all exhibited cotton-like texture and were water-soluble; however, only the precipitated DDBM digest could be gelled. We also found that the method of acetone precipitation could effectively remove salt from the DDBM digest while preserving of multiple proteins from the native bone and internal porous structure. A total of 57 proteins were identified by mass spectrometry in the precipitated DDBM digest and the majority of these proteins are critical to overall protein assembly, scaffold structure and stability, and cell-activities. Additionally, the precipitated DDBM digest possessed enhanced biocompatibility and osteointegration in repairing a cranial bone defect in Sprague-Dawley (SD) rat. In conclusion, the soluble, biodegradable, and biocompatible natures of the precipitated DDBM digest allow its usage in bone tissue engineering as a protein carrier because of its resemblance to native bone-like protein composite and operative flexibility.

Polymer-integrated amnion scaffold significantly improves cleft palate repair.

Cleft palate is a common oral and craniomaxillofacial birth defect. As the ideal surgery time is shortly after birth, clinical treatments should result in minimal disruption of theskeleton to allow tissue growth in children. A tissue-engineered graft was created in this study for cleft palate repair by integrating poly(1,8-octamethylene-citrate) (POC) with a decellularized amnion membrane (DAM-POC) to incorporate the advantages of both the synthetic polymer and the native tissue. The success of POC incorporation was confirmed by laser-induced breakdown spectroscopy and fluorescence detection. The DAM-POC scaffold showed a certain level of structure collapse and lower stiffness but better resistance to enzyme digestion than the native amnion and DAM scaffold. The DAM-POC scaffold is cell compatible when seeded with mesenchymal stem cells, as evidenced by adequate cell viability and improved alkaline phosphatase (ALP) activity and calcium deposit. A large palate defect was first surgically created in a young rat model and then repaired with the DAM-POC scaffold. Eight weeks postsurgery, histological study and CT scans showed nearly complete healing of both soft and hard tissues. In conclusion, we developed a cell-free, resorbable graft by incorporating and integrating a synthetic polymer with a human DAM. When the DAM-POC scaffold was applied to repair a large palate defect in young rats, it showed adequate biocompatibility as evidenced by its effectiveness in guiding hard and soft tissue regeneration and minimum interference with natural growth and palate development of rats. STATEMENT OF SIGNIFICANCE: Proper restoration of severe cleft palate remains a major challenge because of insufficient autologous soft tissues to close the open wounds, thereby causing high tension at the surgical junction, secondary palatal fistulas, wound contraction, scar tissue formation, and facial growth disturbances. In this study, we have developed a tissue-engineered graft through incorporating and integrating a synthetic polymer with the human amnion membrane for cleft palate repair. The significance of this study lies in our ability to develop a cell-free, resorbable graft that can provide a less surgically invasive option to cover the open defect and support palate regeneration and tissue growth. This technique could potentially advance soft and hard tissue regeneration in children with birth craniomaxillofacial defects.

Silver polyvinyl pyrrolidone nanoparticles exhibit a capsular polysaccharide influenced bactericidal effect against Streptococcus pneumoniae.

Streptococcus pneumoniae remains a leading cause of morbidity and mortality worldwide. The highly adaptive nature of S. pneumoniae exemplifies the need for next generation antimicrobials designed to avoid high level resistance. Metal based nanomaterials fit this criterion. Our study examined the antimicrobial activity of gold nanospheres, silver coated polyvinyl pyrrolidone (AgPVP), and titanium dioxide (TiO2) against various serotypes of S. pneumoniae. Twenty nanometer spherical AgPVP demonstrated the highest level of killing among the tested materials. AgPVP (0.6 mg/mL) was able to kill pneumococcal serotypes 2, 3, 4, and 19F within 4 h of exposure. Detailed analysis of cultures during exposure to AgPVP showed that both the metal ions and the solid nanoparticles participate in the killing of the pneumococcus. The bactericidal effect of AgPVP was lessened in the absence of the pneumococcal capsular polysaccharide. Capsule negative strains, JD908 and RX1, were only susceptible to AgPVP at concentrations at least 33% higher than their respective capsule expressing counterparts. These findings suggest that mechanisms of killing used by nanomaterials are not serotype dependent and that the capsular polysaccharide participates in the inhibition. In the near future these mechanisms will be examined as targets for novel antimicrobials.

Development of a LIBS assay for the detection of Salmonella enterica serovar Typhimurium from food.

Laser-induced breakdown spectroscopy (LIBS) is used for the identification of the presence of hazardous bacteria in food. In this study, our main focus was centered on the identification of S. enterica serovar Typhimurium, a Gram-negative foodborne pathogen, in various liquids such as milk, chicken broth, and brain heart infusion due to the infection being most prevalent in raw meat and dairy products. A Nd:YAG laser of operating wavelength 266 nm was used to obtain the spectra from the artificially inoculated liquid samples. A series of experiments were performed to determine the effectiveness of LIBS to discriminate the bacteria from the background liquids. These results are compared with competing modern molecular methods of detection which include polymerase chain reaction (PCR) and quantitative real-time PCR. In addition to analyzing S. enterica serovar Typhimurium, another common Gram-negative, Escherichia coli, as well as Gram-positive pathogen, Staphlycoccus auerus, were used to determine the specificity of the LIBS technique.