Respiratory Symptoms of Exposure to Substances in the Workplace among Bulgarian Dental Students: a Self-report Questionnaire Survey.

BACKGROUND: Dental students are at high risk of developing adverse respiratory reactions as a result of their practical work during their dentistry degree program when they come into contact with multiple airborne irritants and allergens. AIM: To estimate the prevalence of respiratory symptoms of exposure to substances in the workplace and associated risk factors in Bulgarian dental students. RESULTS: The prevalence of self-reported respiratory symptoms related to the pre-clinical and clinical training courses of the dentistry program was 12.4%. According to logistic regression analysis, the most important risk factors for work-related respiratory symptoms were a personal history of allergic rhinoconjunctivitis (odds ratio (OR) 6.34, 95% confidence interval (CI): 3.14-12.78), atopic dermatitis (OR 2.81, 95%CI: 1.26-6.26), and exposure to chemicals from dental environment for more than 6 hours a day (OR 3.60, 95%CI: 1.21-10.70). CONCLUSION: The results of this study suggest that work-related respiratory symptoms are frequent among dental students and indicate the need for efforts to establish effective primary preventive programs for occupational respiratory disorders at national level.

Monolayer formed by l-Asp-based gemini surfactants self-assembled in 1D nanostructures.

Herein, studies on the surface activities of newly synthesized l-Asp-based gemini surfactants, both nonionic and anionic, are presented. Conductometry, tensiometry, and the Langmuir-Blodgett (LB) film technique were applied for this purpose. π-A isotherms were obtained with a Langmuir trough and Wilhelmy balance. The structures of the monolayers assembled at the air/water interface and those deposited as LB films were studied via Brewster angle microscopy (BAM) and atomic force microscopy (AFM). The 2D films formed by the anion-active compounds show a well-known pattern of a monolayer film, whereas the nonionogenic amphiphiles have been found to be 1D structures with nano-widths and micro-lengths that align with each other during the process of compression; this is the first study where the organization of 1D fibrils in 2D films during compression is reported. The scanning electron microscopy (SEM) study reveals that 1D nanostructure formation is an intrinsic tendency of these molecules as not only nonionogenic surfactants, but also the anion active representatives have been constructed in the solid state by fibrillary structures.

Phospholipase A2-Induced Remodeling Processes on Liquid-Ordered/Liquid-Disordered Membranes Containing Docosahexaenoic or Oleic Acid: A Comparison Study.

Vesicle cycling, which is an important biological event, involves the interplay between membrane lipids and proteins, among which the enzyme phospholipase A2 (PLA2) plays a critical role. The capacity of PLA2 to trigger the budding and fission of liquid-ordered (L(o)) domains has been examined in palmitoyl-docosahexaenoylphosphatidylcholine (PDPC) and palmitoyl-oleoylphosphatidylcholine (POPC)/sphingomyelin/cholesterol membranes. They both exhibited a L(o)/liquid-disordered (L(d)) phase separation. We demonstrated that PLA2 was able to trigger budding in PDPC-containing vesicles but not POPC ones. The enzymatic activity, line tension, and elasticity of the membrane surrounding the L(o) domains are critical for budding. The higher line tension of Lo domains in PDPC mixtures was assigned to the greater difference in order parameters of the coexisting phases. The higher amount of lysophosphatidylcholine generated by PLA2 in the PDPC-containing mixtures led to a less-rigid membrane, compared to POPC. The more elastic L(d) membranes in PDPC mixtures exert a lower counteracting force against the L(o) domain bending.

Development of 2D and 3D mucus models and their interactions with mucus-penetrating paclitaxel-loaded lipid nanocapsules.

PURPOSE: To study, diffusion through mucus (3D model) of different formulations of paclitaxel loaded lipid nanocapsules (Ptx-LNCs), to interpret the results in the light of LNC behavior at air-mucus interface (2D model). METHODS: LNC surface properties were modified with chitosan or poly(ethylene glycol) (PEG) coatings of different size (PEG 2,000 to 5,000 Da) and surface charges. LNC diffusion through 446 µm pig intestinal mucus layer was studied using Transwell(®). LNCs were spread at the air-water-mucus interface then interfacial pressure and area changes were monitored and the efficiency of triglyceride (TG) inclusion was determined. RESULTS: Ptx-LNCs of surface charges ranging from -35.7 to +25.3 mV were obtained with sizes between 56.2 and 75.1 nm. The diffusion of paclitaxel in mucus was improved after encapsulation in neutral or positively charged particles (p < 0.05 vs Taxol(®)). No significative difference was observed in the 2,000-5,000 PEG length for diffusion both on the 2D or 3D models. On 2D model positive or neutral LNCs interacted less with mucus. Highest efficiency of TG inclusion was observed for particles with smallest PEG length. CONCLUSIONS: The results obtained with 2D and 3D model allowed us to select the best candidates for in vivo studies (neutral or positive LNCs with smaller PEG length).