Cell-derived extracellular vesicles and membranes for tissue repair.

Humans have a limited postinjury regenerative ability. Therefore, cell-derived biomaterials have long been utilized for tissue repair. Cells with multipotent differentiation potential, such as stem cells, have been administered to patients for the treatment of various diseases. Researchers expected that these cells would mediate tissue repair and regeneration through their multipotency. However, increasing evidence has suggested that in most stem cell therapies, the paracrine effect but not cell differentiation or regeneration is the major driving force of tissue repair. Additionally, ethical and safety problems have limited the application of stem cell therapies. Therefore, nonliving cell-derived techniques such as extracellular vesicle (EV) therapy and cell membrane-based therapy to fulfil the unmet demand for tissue repair are important. Nonliving cell-derived biomaterials are safer and more controllable, and their efficacy is easier to enhance through bioengineering approaches. Here, we described the development and evolution from cell therapy to EV therapy and cell membrane-based therapy for tissue repair. Furthermore, the latest advances in nonliving cell-derived therapies empowered by advanced engineering techniques are emphatically reviewed, and their potential and challenges in the future are discussed.

PCR detection of Streptococcus mutans and Aggregatibacter actinomycetemcomitans in dental plaque samples from Haitian adolescents.

Streptococcus mutans and Aggregatibacter actinomycetemcomitans are oral pathogens associated with dental caries and periodontitis, respectively. The aim of this study was to determine the colonization of these two microorganisms in the dental plaque of a group of Haitian adolescents using two different polymerase chain reaction (PCR) methods, standard PCR, and quantitative real-time PCR (qPCR) assays. Fifty-four pooled supra-gingival plaque samples and 98 pooled sub-gingival plaque samples were obtained from 104 12- to19-year-old rural-dwelling Haitians. The total genomic DNA of bacteria was isolated from these samples, and all participants also received caries and periodontal examinations. Caries prevalence was 42.2%, and the mean decayed, missing, and filled surface (DMFS) was 2.67 ± 5.3. More than half of the adolescents (53.3%) experienced periodontal pockets (Community Periodontal Index score ≥3). S. mutans was detected in 67.3% by qPCR and 38.8% by PCR of the supra-gingival plaque samples (p < 0.01), and 36.6% by qPCR and 8.1% by PCR of the sub-gingival samples (p < 0.01). A. actinomycetemcomitans was detected in 85.1% by qPCR and 44.0% by PCR of the sub-gingival samples (p < 0.01), but the prevalence was similar, 67.3% by qPCR and 59.2% by PCR, in the supra-gingival plaque samples. Neither age nor gender was significantly correlated to the bacterial colonization. The results demonstrated a moderate-to-high prevalence of S. mutans and A. actinomycetemcomitans in the Haitian adolescent population, and qPCR is more sensitive than standard PCR in field conditions. These findings suggest that qPCR should be considered for field oral epidemiologic studies and may be necessary in investigations having major logistic challenges.

A conformally adapted all-in-one hydrogel coating: towards robust hemocompatibility and bactericidal activity.

Hospital-acquired infections and thrombosis caused by bacteria attached to the device surface, or fibrin crosslinking owing to platelet accumulation/activation, are major healthcare challenges that cause morbidity and mortality. To prevent these, surface coating technologies are considered an efficient tool that can combine hemocompatibility and bactericidal activity. In this study, surface-initiated polymerization was conducted to form an all-in-one hydrogel coating that could adapt to diverse medical devices. Different monomer ratios (acrylamide/acrylic acid) were used to adjust the antimicrobial agent loading capacity. The hydrogel coating obtained by a simple dip-absorbing method showed good hemocompatibility and maintained efficient bactericidal activity. We also explored the loading and release of antimicrobial agents with different molecular sizes, including nano-Ag particles, antibiotics, and antimicrobial peptides. The inhibition zone test and confocal laser scanning microscopy revealed that the hydrogel coating could maintain remarkable antimicrobial and antifouling properties for four weeks. Furthermore, the hydrogel coating decreased the platelet adhesion/activation without risk of hemolysis. The ex vivo blood circulation study confirmed the antithrombotic properties of the hydrogel coating. Such all-in-one hydrogel coatings that maintain high cell viability and exhibit both hemocompatibility and bactericidal activity possess the potential for applications in blood-contacting devices.

Dual drug loaded coaxial electrospun PLGA/PVP fiber for guided tissue regeneration under control of infection.

Electrospinning promisingly fabricate mats for Guided Tissue Regeneration (GTR). Due to a chronic inflammatory pathology in periodontal, it is highly desirable to develop a novel GTR mats to realize tissue regeneration under control of infection. In the study, coaxial electrospinning was firstly conducted to fabricate dual drug loaded fiber mats with core/shell structure. Naringin-loaded polyvinylpyrrolidone was designed as core fiber to enrich tissue regeneration and metronidazole-loaded poly(lactic-co-glycolic acid) as shell fiber to inhibit bacterial. TEM revealed that the fibers with distinct core/shell structure were in an outer diameter of 1.5-1.7 µm with an inner diameter of <1.0 µm. The loading of dual drug decreased the tensile strength and elongation of the coaxial fiber mats. On in vitro assessment, metronidazole had a short-term release while naringin had a long-term release behavior in all the coaxial mats. The colonization of anaerobic bacteria on the mats effectively were inhibited over 21 days. Furthermore, the dual drug loaded coaxial fiber mats were observed to positively supported the adhesion and proliferation of MC3T3-E1 and was conductive to high alkaline phosphatase express. Thus, a simple and effective coaxial electrospinning approach was demonstrated for the fabrication of anti-infective GTR mats with promoting tissue regeneration.

Development of species-specific primers for detection of Streptococcus mutans in mixed bacterial samples.

Streptococcus mutans is the major microbial pathogen associated with dental caries in children. The objectives of this study were to design and evaluate species-specific primers for the identification of S. mutans. Validation of the best primer set, Sm479F/R, was performed using seven S. mutans reference strains, 48 ATCC non-S. mutans strains, 92 S. mutans clinical isolates, DNA samples of S. mutans-Streptococcus sobrinus or S. mutans-Streptococcus sanguinis, and mixed bacterial DNA of saliva samples from 33 18-month-old children. All of the S. mutans samples tested positive, and no PCR products were amplified from members of the other streptococci or nonstreptococci strains examined. The lowest detection level for PCR was 10(-2) ng of S. mutans DNA (c. 4.6 x 10(3) copies) in the test samples. The results of this study suggest that the Sm479F/R primer pair is highly specific and sensitive for identification of S. mutans in either purified or mixed DNA samples.

Polypropylene injection molded part with novel macroscopic bamboo-like bionic structure.

A macroscopic bamboo-like bionic structure was fabricated in the injection-molded bar of isotactic polypropylene via the combined effect of "melt manipulation" and beta-nucleator. Such structure consists of strengthened shell zone with high orientation and low beta-phase amount, and toughened core part with isotropic texture and dominant beta-modification. The influences of shear intensity on structural hierarchies, polymorphism, and crystalline morphology were estimated. Both toughness and strength can be significantly improved with increasing shear intensity on the bamboo-like structure. Our study suggested an alternative approach to achieve excellent comprehensive mechanics in polypropylene via macroscopic structural design during the practical molding process.

Similarity of bacterial populations in saliva from African-American mother-child dyads.

Using PCR-based denaturing gradient gel electrophoresis analyses of oral bacterial samples in 20 mother-child dyads, this study demonstrated a high degree of similarity of bacterial compositions between the mothers and their children; the two may share as much as 94% of their oral bacterial spectra, including cariogenic species.

[Evaluation of acid diffusion and fluoride selective electrode to measure the total fluoride in toothpastes].

OBJECTIVE: To evaluate the reliability of a method of measuring the total fluoride in fluoride-containing toothpastes with acid diffusion and fluoride selective electrode. METHODS: Four brands of commercially available non-fluoride toothpastes and fluoride-containing toothpastes were sampled. Fluoride was extracted from the toothpastes in 2 mol/L HC10(4) at room temperature overnight and then subjected to the measurement with fluoride electrode. RESULTS: Fluoride recovery of the non-fluoride toothpastes containing calcium as abrasive by this method was 99.5%-100.5%, more than 94% of total fluoride was measured from the marketed fluoride toothpastes, and the variation coefficient of this method was less than 1.54%. While the abrasive was silicon, the fluoride recovery of the non-fluoride toothpastes was 83.4%, and 89.7% of total fluoride was measured from the marketed fluoride-containing toothpastes. CONCLUSION: The amount of total fluoride in the calcium containing toothpaste can be detected simply and accurately measured by acid diffusion and fluoride selective electrode.