Tunable protein-resistance of polycation-terminated polyelectrolyte multilayers

The prevention of nonspecific protein adsorption is a crucial prerequisite for many biomedical and biotechnological applications. Therefore, the design of robust and versatile methods conferring optimal protein-resistance properties to surfaces has become a challenging issue. Here we report the unexpected case of polycation-ending polyelectrolyte multilayers (PEM) that efficiently prevented the adsorption of a negatively charged model protein, glucose oxidase (GOX). PEM films were based on two typical weak poyelectrolytes: poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). No chemical modification of the polyelectrolytes was required and tunable GOX adsorption was possible by simply changing the buildup pH conditions. Protein-resistance properties are attributed to high film hydration becoming the predominant factor over electrostatic interactions. We explain this effect by oscillations of the internal PAA ionization state throughout the buildup, which results in an excess of carboxylic acid groups within the film. This excess acts as a reservoir of potential carboxylate groups compensating the outer PAH positive charges. Partial results indicated that the system was also resistant to the adsorption of a positively charged protein, lysozyme. Control of the internal ionization of weak polyelectrolyte multilayers might open a route toward simple tuning of protein adsorption. These results should help to rationalize the design of biomaterials, biosensors, or protein separation devices.

Proteomic Studies of Saliva: A Proposal for a Standardized Handling of Clinical Samples

Background

In recent years, differential analysis of proteins from human saliva, i.e., proteomic analysis, has received much attention mainly due to its unstressful sampling and its great potential for biomarker research. It is widely considered that saliva is a highly stable medium for proteins thanks to a large amount of antiprotease agents, even at ambient and physiological temperatures.

Objective

To find the best protocol for the handling of samples, we have investigated the stability of saliva proteins stored at different temperatures (from −80 to 20°C) by one- and two-dimensional electrophoresis.

Results

At 20°C, no major changes were observed on protein one-dimensional profiles following 1 day of storage; however, between 7 days and 30 days, the native alpha-amylase band decreased slightly to give several bands with molecular weight between 35 and 25 kDa. The same phenomenon appeared after 30 days of storage at 4°C. Two-dimensional analysis of salivary maps revealed degradation from day 7 of several protein groups for samples stored at 20°C.

Conclusion

All these findings have to be carefully considered when saliva is collected for clinical proteomic analysis. We can conclude that, to maintain the optimum stability of saliva proteins, saliva samples should be collected on ice followed by the addition of protease inhibitor cocktail, centrifuged to remove insoluble material, and stored at −20 or −80°C.

Human osteoblast response to pulsed laser deposited calcium phosphate coatings

Octacalcium phosphate (OCP) and Mn(2+)-doped carbonate hydroxyapatite (Mn-CHA) thin films were deposited on pure, highly polished and chemically etched Ti substrates with pulsed laser deposition. The coatings exhibit different composition, crystallinity and morphology that might affect their osteoconductivity. Human osteoblasts were cultured on the surfaces of OCP and Mn-CHA thin films, and the cell attachment, proliferation and differentiation were evaluated up to 21 days. The cells showed a normal morphology and a very good rate of proliferation and viability in every experimental time. Alkaline phosphatase activity was always higher than the control and Ti groups. From days 7 to 21 collagen type I production was higher in comparison with control and Ti groups. The level of transforming growth factor beta 1 (TGF-beta1) was lower at 3 and 7 days, but reached the highest values during following experimental times (14 and 21 days). Our data demonstrate that both calcium phosphate coatings favour osteoblasts proliferation, activation of their metabolism and differentiation.

A possible role of collagen fibrils in the process of calcification observed in the capsule of the pineal gland in aging rats

The relationship between collagen fibrils and calcified concretions exclusively appearing in the pineal gland of adult/aging rats has been investigated. Deposits of lanthanum, which replace calcium ions are distributed along collagen fibrils with a repeating period of about 70 nm. Calcium has been detected histochemically between collagen bundles surrounding extracellular concretions by means of the pyroantimonate method and by X-ray microanalysis. It is associated with phosphorus. The data presented here suggest that collagen fibrils are involved in the genesis and growth of extracellular concretions located in the connective tissue surrounding the pineal gland of aging rats.

Prevalence of six periodontal pathogens detected by DNA probe method in HIV vs non-HIV periodontitis

OBJECTIVE

The aim of the study was to examine the prevalence of selected periodontal pathogens associated with HIV and non-HIV related periodontal lesions.

METHODS

Subgingival plaque samples were obtained from both HIV-seropositive and HIV-seronegative patients affected with periodontal disease. DNA probes were used to detect Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Bacteroides forsythus, Eikenella corrodens and Campylobacter rectus.

RESULTS

A actinomycetemcomitans, P. intermedia and B. forsythus (P < 0.05) were more prevalent in HIV-seronegative patients with rapidly progressive periodontitis. Only C. rectus was slightly more prevalent in HIV-seropositive subjects with periodontal diseases, but this was not significant.

[Antigen presenting cells during periodontal disease]

The macrophages have an important function in the presentation of the antigen to the T lymphocytes. This presentation mandatory for the activation of the T lymphocytes is described. The Langerhans cells also play a role in the antigen presentation. These cells especially in the oral mucosa have been studied during the last years.

[Guided tissue regeneration: ultrastructure of membranes and review of the literature]

Guided tissue regeneration is an innovative new technique designed to encourage healing of the periodontium by blocking out gingival epithelium and connective tissue from the healing wound. The various types of membranes used in guided tissue regeneration are described and a scanning electron microscopic study of the membranes is presented.

[Characteristics of certain early periodontitis: apropos of two cases]

The study of early onset periodontitis led in the last years to important improvement in the etiopathogenic knowledge of periodontitis. The clinical and microbiological analysis of 2 early onset periodontitis cases gives a better understanding of the evolution of these 2 models of periodontal lesions. Hypothesis are presented concerning the transition between localized juvenile periodontitis and rapidly advanced periodontitis.

Transmission electron microscopy of lattice planes in human alveolar bone apatite crystals

Periodic fringes corresponding to six different lattice planes have been observed in apatite crystals of human normal alveolar bone by transmission electron microscopy. Three of these sets of fringes have spacings less than 3.5 A corresponding to the Scherzer resolution of the microscope used. The (0002) lattice plane of hydroxyapatite of 3.4 A d-spacings, the (2111) lattice plane with a d-spacing of 2.81 A, and the (3030) lattice plane with a d-spacing of 2.72 A have been identified. The (0002) and (2121) lattice planes have been observed for the first time in bone microcrystals. Some of the crystals studied were characterized by a mean width/thickness ratio of 6.91, typical of platelike habit, whereas observations of crystals aligned along the (1210) and (1211) directions showed a needlelike habit. The mean length of the bone apatite crystals was 470 A. A dark line similar to the one observed in enamel and dentine crystals was also seen. The bone microcrystals observed have shown a high sensitivity to beam damage.