Formation and photocatalytic decomposition of a pellicle on anatase surfaces

The acquired dental pellicle plays a critical role in the adhesion and detachment of dental plaque bacteria. It has been reported that titanium dioxide biomaterials decompose single-protein films by photocatalysis. However, it is not known whether this can also be achieved with complex structured pellicle films. This in vitro study investigated in real-time the formation and photocatalytic decomposition of human pellicle at anatase-saliva interfaces. Nanostructured polycrystalline anatase layers were deposited on titanium-coated quartz crystals by magnetron-sputtering, serving as a model for titanium implant surfaces. The quartz crystals were used as acoustic sensors in a quartz-crystal microbalance (QCM) system with dissipation. In situ UV irradiation of pellicle-covered anatase caused a statistically significant decrease of the adsorbed salivary mass. In contrast, photocatalytic decomposition of pellicle could not be observed on reference titanium surfaces. Wettability characterization revealed superhydrophilicity of anatase upon UV irradiation, whereas titanium was unaffected. XPS measurements provide further information concerning the decomposition of the salivary films. The results suggest that the photocatalytic activity of polycrystalline anatase-modified biomaterial surfaces is able to decompose complex structured macromolecular pellicle films. Therefore, this study opens the way to surface modifications supporting therapeutic approaches of biofilm removal.

The prevalence of radiologic TMJ findings and self-reported orofacial pain in a patient group wearing implant dentures

PURPOSE

This study had a twofold aim: first, to gather knowledge about the prevalence of radiologic signs of temporomandibular joint osteoarthritis (TMJ-OA) and possible risk factors in patients who had worn an implant prosthesis for between 2.5 and 10 years; and second, to investigate the diagnostic value of radiologic TMJ-OA signs for orofacial pain in a non-temporomandibular disorders group.

MATERIALS AND METHODS

Two hundred thirty patients (134 women, 96 men) answered a questionnaire regarding orofacial pain. In mean, they were 64 years old and wore 98 fixed and 132 removable implant dentures. The effect of age, gender, state of the dentition, time span after prosthesis placement, parafunction, and TMJ sounds on radiologic TMJ-OA signs was estimated through multiple logistic regression. The predictive values were calculated to assess the diagnostic value of severe TMJ-OA signs to predict orofacial pain.

RESULTS

Prevalence of TMJ-OA signs was 70% for flattening, 23% for osteophytes, and 24% for erosion. Some effect on radiologic TMJ-OA signs of gender and state of the dentition was found. The predictive values for orofacial pain from radiologic TMJ-OA ranged from 0.22 to 0.81.

CONCLUSION

Radiologic signs of TMJ-OA were common findings. The study gave no indication that long-term wearing of an implant prosthesis has a negative effect on TMJ-OA. It was not possible to predict orofacial pain from radiologic TMJ-OA signs.

Intergeneric poliovirus recombinants for the treatment of malignant glioma

Poliovirus neuropathogenicity depends on sequences within the 5' nontranslated region of the virus. Exchange of the poliovirus internal ribosomal entry site with its counterpart from human rhinovirus type 2 resulted in attenuation of neurovirulence in primates. Despite deficient virus propagation in cells of neuronal origin, nonpathogenic polio recombinants retain excellent growth characteristics in cell lines derived from glial neoplasms. Susceptibility of malignant glioma cells to poliovirus may be mediated by expression of a poliovirus receptor, CD155, in glial neoplasms. Intergeneric polio recombinants with heterologous internal ribosomal entry site elements unfolded strong oncolytic potential against experimentally induced gliomas in athymic mice. Our observations suggest that highly attenuated poliovirus recombinants may have applicability as biotherapeutic antineoplastic agents.

New chimaeric hepatitis B virus core particles carrying hantavirus (serotype Puumala) epitopes: immunogenicity and protection against virus challenge

Virus-like particles generated by the heterologous expression of virus structural proteins are able to potentiate the immunogenicity of foreign epitopes presented on their surface. In recent years epitopes of various origin have been inserted into the core antigen of hepatitis B virus (HBV) allowing the formation of chimaeric HBV core particles. Chimaeric core particles carrying the 45 N-terminal amino acids of the Puumala hantavirus nucleocapsid protein induced protective immunity in bank voles, the natural host of this hantavirus. Particles applied in the absence of adjuvant are still immunogenic and partially protective in bank voles. Although a C-terminally truncated core antigen of HBV (HBcAg delta) tolerates the insertion of extended foreign sequences, for the construction of multivalent vaccines the limited insertion capacity is still a critical factor. Recently, we have described a new system for generating HBV 'mosaic particles' in an Escherichia coli suppressor strain based on a readthrough mechanism on a stop linker located in front of the insert. Those mosaic particles are built up by both HBcAg delta and the HBcAg delta/Puumala nucleocapsid readthrough protein. The particles formed presented the 114 amino acid (aa) long hantavirus sequence, at least in part, on their surface and induced antibodies against the hantavirus sequence in bank voles. Variants of the stop linker still allowed the formation of mosaic particles demonstrating that stop codon suppression alone is sufficient for the packaging of longer foreign sequences in mosaic particles. Another approach to increase the insertion capacity is based on the simultaneous insertion of different Puumala nucleocapsid protein sequences (aa 1-45 and aa 75-119) into two different positions (aa 78 and behind aa 144) of a single HBcAg molecule. The data presented are of high relevance for the generation of multivalent vaccines requiring a high insertion capacity for foreign sequences.

Characterization of potential insertion sites in the core antigen of hepatitis B virus by the use of a short-sized model epitope

Core particles of hepatitis B virus (HBV) are able to improve the immunogenicity of foreign sequences exposed on the particle surface. The insertion site in the core antigen of HBV (HBcAg) determines the surface presentation and thus the immunogenicity of the foreign sequence. For direct comparison of the value of potential insertion sites in the core antigen, we constructed vectors allowing insertions of a model marker epitope DPAFR. This epitope was inserted at the N-terminus, the c/e1 loop, behind amino acid (aa) 144 and behind aa 183 (DPAF only). In addition, we generated a mosaic construct allowing the co-expression of HBcAg and a HBcAg/DPAFR fusion protein due to a suppressor tRNA-mediated readthrough mechanism. All 6 constructs allowed the formation of chimaeric or mosaic core-like particles. Western blot analyses and a direct ELISA demonstrated the presence of the DPAFR sequence in the chimaeric and mosaic particles. Competitive ELISA and immune electron-microscopic data suggested the c/e1 loop as the insertion site of choice for presenting foreign sequences on the surface of chimaeric HBV core particles. However, the N-terminal fusion also allowed partial surface exposure of the DPAFR motif. In contrast, in particles of constructs carrying the DPAFR insert at aa position 144 or 183, respectively, the epitope seemed not to be surface accessible.