Pore size is a critical parameter for obtaining sustained protein release from electrochemically synthesized mesoporous silicon microparticles.

Mesoporous silicon has become a material of high interest for drug delivery due to its outstanding internal surface area and inherent biodegradability. We have previously reported the preparation of mesoporous silicon microparticles (MS-MPs) synthesized by an advantageous electrochemical method, and showed that due to their inner structure they can adsorb proteins in amounts exceeding the mass of the carrier itself. Protein release from these MS-MPs showed low burst effect and fast delivery kinetics with complete release in a few hours. In this work, we explored if tailoring the size of the inner pores of the particles would retard the protein release process. To address this hypothesis, three new MS-MPs prototypes were prepared by electrochemical synthesis, and the resulting carriers were characterized for morphology, particle size, and pore structure. All MS-MP prototypes had 90 µm mean particle size, but depending on the current density applied for synthesis, pore size changed between 5 and 13 nm. The model protein α-chymotrypsinogen was loaded into MS-MPs by adsorption and solvent evaporation. In the subsequent release experiments, no burst release of the protein was detected for any prototype. However, prototypes with larger pores (>10 nm) reached 100% release in 24-48 h, whereas prototypes with small mesopores (<6 nm) still retained most of their cargo after 96 h. MS-MPs with ∼6 nm pores were loaded with the osteogenic factor BMP7, and sustained release of this protein for up to two weeks was achieved. In conclusion, our results confirm that tailoring pore size can modify protein release from MS-MPs, and that prototypes with potential therapeutic utility for regional delivery of osteogenic factors can be prepared by convenient techniques.

Obstructive sleep apnoea in the elderly: role of continuous positive airway pressure treatment.

Almost all the information about the effect of continuous positive airway pressure (CPAP) in patients with obstructive sleep apnoea (OSA) comes from clinical trials involving only middle-aged patients. The objective of this study was to assess the effect of CPAP treatment in elderly patients with severe OSA on clinical, quality-of-life and neurocognitive spheres. We performed an open-label, randomised, multicentre clinical trial in a consecutive clinical cohort of 224 elderly (≥70 years old) patients with confirmed severe OSA (apnoea-hypopnea index ≥30) randomised to receive CPAP (n=115) or no CPAP (n=109) for 3 months. A sleep study was performed by either full polysomnography or respiratory polygraphy. CPAP titration was performed by an autoCPAP device. The primary endpoint was quality of life (Quebec Sleep Questionnaire) and secondary endpoints included sleep-related symptoms, presence of anxiety/depression, office-based blood pressure and some neurocognitive tests. The mean±sd age was 75.5±3.9 years. The CPAP group achieved a greater improvement in all quality-of-life domains (p<0.001; effect size: 0.41-0.98), sleep-related symptoms (p<0.001; effect size 0.31-0.91) as well as anxiety (p=0.016; effect size 0.51) and depression (p<0.001; effect size: 0.28) indexes and some neurocognitive tests (digit symbol test (p=0.047; effect size: 0.20) and Trail Making Test A (p=0.029; effect size: 0.44)) in an intention-to-treat analysis. In conclusion, CPAP treatment resulted in an improvement in quality of life, sleep-related symptoms, anxiety and depression indexes and some neurocognitive aspects in elderly people with severe OSA.

Protein delivery based on uncoated and chitosan-coated mesoporous silicon microparticles.

Mesoporous silicon is a biocompatible, biodegradable material that is receiving increased attention for pharmaceutical applications due to its extensive specific surface. This feature enables to load a variety of drugs in mesoporous silicon devices by simple adsorption-based procedures. In this work, we have addressed the fabrication and characterization of two new mesoporous silicon devices prepared by electrochemistry and intended for protein delivery, namely: (i) mesoporous silicon microparticles and (ii) chitosan-coated mesoporous silicon microparticles. Both carriers were investigated for their capacity to load a therapeutic protein (insulin) and a model antigen (bovine serum albumin) by adsorption. Our results show that mesoporous silicon microparticles prepared by electrochemical methods present moderate affinity for insulin and high affinity for albumin. However, mesoporous silicon presents an extensive capacity to load both proteins, leading to systems were protein could represent the major mass fraction of the formulation. The possibility to form a chitosan coating on the microparticles surface was confirmed both qualitatively by atomic force microscopy and quantitatively by a colorimetric method. Mesoporous silicon microparticles with mean pore size of 35 nm released the loaded insulin quickly, but not instantaneously. This profile could be slowed to a certain extent by the chitosan coating modification. With their high protein loading, their capacity to provide a controlled release of insulin over a period of 60-90 min, and the potential mucoadhesive effect of the chitosan coating, these composite devices comprise several features that render them interesting candidates as transmucosal protein delivery systems.

The influence of platform switching in dental implants. A literature review

Introduction: The platform switching concept involves the reduction of the restoration abutment diameter withrespect to the diameter of the dental implant.In 1991, dental implants of 5 and 6 mm diameter platforms were introduced. However, matching-diameter prostheticabutments were not available. These implants were restored with “standard”-diameter prosthetic components(4,1 mm).Long-term follow up around these wide-platforms showed higher levels of bone preservation. In time, it has beencalled platform switching. The first case report applying this concept was indexed in MedLine in 2005.Materials and Methods: The aim of this article is to carry out a literature review of articles which deal with theinfluence of this modified platform in hard and soft oral tissues. All papers involving “platform switching” thatare indexed in MedLine and published in English were used. Clinical cases, experimental and non-experimentalstudies were included, as well as literature reviews.Results: In our search, we found: 16 clinical series or single clinical cases, 10 test and control studies, 9 experimentalstudies and 3 reviews.Conclusion: All papers written by different researchers show an improvement in perimplant bone preservation.Further long-term studies are necessary to confirm these results.The articles consulted refer to the biomechanical behavior of the abutment-implant complex in response to occlusalloading, the maintenance of crestal bone height and the peculiar repositioning of the biological space (AU)

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The influence of platform switching in dental implants. A literature review.

INTRODUCTION: The platform switching concept involves the reduction of the restoration abutment diameter with respect to the diameter of the dental implant. In 1991, dental implants of 5 and 6 mm diameter platforms were introduced. However, matching-diameter prosthetic abutments were not available. These implants were restored with "standard"-diameter prosthetic components (4.1 mm). Long-term follow up around these wide-platforms showed higher levels of bone preservation. In time, it has been called platform switching. The first case report applying this concept was indexed in MedLine in 2005. MATERIALS AND METHODS: The aim of this article is to carry out a literature review of articles which deal with the influence of this modified platform in hard and soft oral tissues. All papers involving "platform switching" that are indexed in MedLine and published in English were used. Clinical cases, experimental and non-experimental studies were included, as well as literature reviews. RESULTS: In our search, we found: 16 clinical series or single clinical cases, 10 test and control studies, 9 experimental studies and 3 reviews. CONCLUSION: All papers written by different researchers show an improvement in perimplant bone preservation. Further long-term studies are necessary to confirm these results. The articles consulted refer to the biomechanical behavior of the abutment-implant complex in response to occlusal loading, the maintenance of crestal bone height and the peculiar repositioning of the biological space.

Porous silicon for photosensitized formation of singlet oxygen in water and in simulated body fluid: two methods of modification by undecylenic acid.

Initially H-terminated and therefore hydrophobic surface of electrochemically prepared luminescent porous silicon (PSi) powder was transformed to the hydrophilic one by means of surface modification by undecylenic acid. Physical adsorption of undecylenic acid as a non-ionic surfactant and its chemical binding through C[triple bond]C bond opening and Si-C bond formation were applied as two different methods of PSi surface modification, physical and chemical modification, respectively. Luminescence of aqueous suspensions of the both types of modified PSi powders in merely water and in simulated body fluid physiological electrolyte was measured as a function of time. Many-fold (up to 20 times) building-up of the luminescence intensity was observed for PSi aqueous suspensions during the first few days, the growth was followed by a slower (a week and more) luminescence intensity decay. As it is evidenced by FTIR spectra and SEM images, the effect of the luminescence growth and decay of PSi suspension in water can be in part attributed to the PSi surface oxidation accompanied by its dissolution and de-aggregation of large PSi particles. It is concluded also from the experiments on PSi luminescence reversible quenching by O2 that SiO-related surface states with the excitation energy about 2.2 eV are formed during water-assisted oxidation of Si nanocrystal surface. An appearance of a large number of such surface states can be also responsible for the observed PSi luminescence building-up.