Antimicrobial effect of nanostructured membranes for guided tissue regeneration: an in vitro study

Biomaterials for Guided Tissue Regeneration and Guided Bone Regeneration: A Review

This review aims to provide an overview of the types of membranes, bone substitutes, and mucosal substitutes used for GTR and GBR and briefly explores recent innovations for tissue regeneration and their future perspectives. Since this is a narrative review, no systematic search, meta-analysis, or statistical analysis was conducted. Using biomaterials for GTR and GBR provides a reduction in postoperative morbidity, as it contributes to less invasive clinical procedures, serving as an alternative to autogenous grafts. Moreover, randomized clinical trials (RCTs) and systematic reviews are essential for the evaluation of new biomaterials. These studies provide more robust evidence and help guide clinical practice in the selection of safer and more effective biomaterials, allowing for the personalization of treatment protocols for each patient.

In vitro efficacy of photodynamic therapy with toluidine blue for decontamination of resorbable membranes inoculated with Streptococcus mutans

OBJECTIVES

This study assessed the efficacy of antimicrobial photodynamic therapy (aPDT) with toluidine blue (TB) for decontamination of resorbable membranes inoculated with Streptococcus mutans (S. mutans).

MATERIALS AND METHODS

In this in vitro study, Mucoderm and Jason resorbable membranes were cut into 15 pieces each, and were inoculated with S. mutans at 105 colony forming units (CFUs)/mL concentration. The membranes were subsequently assigned to 3 subgroups each (n = 5), for decontamination with TB (100 µg/mL) activated by 635 nm laser (60 s) as the experimental group (aPDT), 0.12 % chlorhexidine (CHX) as the positive control, and phosphate buffered saline (PBS) as the negative control. Changes in colony count after the interventions were calculated. Data were analyzed by the Kruskal-Wallis and Dunn's tests (alpha=0.05).

RESULTS

In both membrane types, the difference in colony count was significant among the three subgroups (P = 0.002). The lowest colony count was noted in the CHX subgroup, and the highest was recorded in the PBS subgroup. aPDT caused a significant reduction in colony count compared with the negative control group (P = 0.002). Significant differences were found between all three groups in pairwise comparisons (P < 0.05). The efficacy of aPDT was not significantly different for decontamination of the two membrane types (P = 635).

CONCLUSION

aPDT with 635 nm diode laser and TB had optimal efficacy (although inferior to CHX) for decontamination of both Jason and Mucoderm resorbable membranes inoculated with S. mutans.

Development and characterization of nitazoxanide-loaded poly(ε-caprolactone) membrane for GTR/GBR applications

OBJECTIVE

Guided tissue/guided bone regeneration (GTR/GBR) membranes are widely used for periodontal bone regeneration, but their success depends on a bacteria-free environment. Systemic antibiotic treatment often proves inadequate, moreover, the increasing prevalence of antibiotic resistance in oral infections exacerbates this challenge. This study aimed to fabricate antibacterial membranes using a new class of antibiotics for local drug delivery, to eradicate infections and promote tissue regeneration.

METHODS

Membranes loaded with nitazoxanide (NTZ) were fabricated via electrospinning using poly(ε-caprolactone) (PCL) with varying concentrations of NTZ (0 %, 2.5 %, and 5 % w/w) relative to the polymer weight. Morphochemical of NTZ-loaded membranes were assessed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier Transform Infrared spectroscopy (FTIR). Mechanical properties were evaluated using universal testing machine and NTZ release profile from membranes was determined by spectrophotometer (λmax = 444) for 14 days. Antimicrobial efficacy against periodontal pathogens, cell compatibility and mineralization were evaluated using periodontal ligament stem cells (PDLSCs).

RESULTS

Optimized spinning parameter maintained a uniform fiber diameter and successful loading of NTZ was confirmed by SEM-EDS and FTIR. NTZ incorporation did not significantly affect mechanical properties, whereas the drug release kinetics showed an initial burst, followed by sustained release over 14 days. NTZ-loaded membranes demonstrated antibacterial activity against Aggregatibacter actinomycetemcomitans (Aa) and Fusobacterium nucleatum (Fn). Importantly, the presence of NTZ showed minimal cell toxicity; however, it reduced the mineralization potential compared with that of the pure PCL membrane, which increased over time.

SIGNIFICANCE

Taken together, these findings established that NTZ-loaded membranes could be promising barrier membrane to counteract microbial environment and aid periodontal bone regeneration.

In Vitro Degradation of Collagen-Based Membranes for Guided Bone Regeneration After Zn-Ions or Doxycycline Functionalization

Collagen-based membrane is the most commonly used biomaterial for guided bone and tissue regeneration; however, its barrier function can be threatened by its rapid degradation pattern, affecting the success of the regeneration process. Differences in the origin and functionalization of the membrane to obtain better properties can alter the degradation rate. The objective of this study was to examine the biodegradation pattern of two commercially available collagen membranes (Jason® and Collprotect®) manufactured using porcine pericardium or dermis, doped or not with zinc-ions or doxycycline, in a period up to 21 days. The membrane specimens were subjected to hydrolytic and bacterial degradation tests. The different immersion times were carried out from 12 h up to 21 days. At each time point, quantitative measurements of thickness and weight were made using a digital caliper and an analytic microbalance, respectively. ANOVA and Student-Newman-Keuls tests were carried out for comparison purposes (p < 0.05). The differences between time-points within the same membranes and solutions were assessed by pairwise comparisons (p < 0.001). Unfunctionalized Jason membrane made of porcine pericardium attained the highest resistance to both degradation tests. The functionalization of the membranes did not alter the biodegradation patterns. All the membranes completely degraded before 48 h in the bacterial collagenase solution, which was the most aggressive test.

Microbial colonization in the partially exposed nonabsorbable membrane during alveolar ridge preservation

AIM

This study evaluated the impact of the partial exposition of the nonabsorbable membrane (dPTFE) on microbial colonization during bone healing.

MATERIALS AND METHODS

Patients indicated for tooth extraction were randomized to dPTFE group (n = 22) - tooth extraction and alveolar ridge preservation (ARP) using an intentionally exposed dPTFE membrane and USH group (n = 22) - tooth extraction and unassisted socket healing. Biofilm samples were collected at the barrier in the dPTFE and on the natural healing site in the USH after 3 and 28 days. Samples from the inner surface of the dPTFE barrier were also collected (n = 13). The microbiome was evaluated using the Illumina MiSeq system.

RESULTS

Beta diversity was different from 3 to 28 days in both groups, and at 28 days, different microbial communities were identified between therapies. The dPTFE was characterized by a higher prevalence and abundance of gram-negative and anaerobic species than USH. Furthermore, the inner surface of the dPTFE membrane was colonized by a different community than the one observed on the outer surface.

CONCLUSION

Intentionally exposed dPTFE membrane modulates microbial colonization in the ARP site, creating a more homogeneous and anaerobic community on the inner and outer surfaces of the membrane.

CLINICAL RELEVANCE

DPTFE promoted faster biofilm colonization and enrichment of gram-negative and anaerobes close to the regenerated site in the membrane's inner and outer surfaces. dPTFE membrane can be used exposed to the oral site, but approaches for biofilm control should still be considered. The study was retrospectively registered at Clinicaltrials.gov (NCT04329351).

Attachment and proliferation of human gingival fibroblasts seeded on barrier membranes using Wharton's jelly-derived stem cells conditioned medium: An in vitro study

The effect of Wharton's jelly mesenchymal stem cells conditioned medium (WJMSCs-CM) and zinc oxide nanoparticles (ZnO-NPs) on cultured human gingival fibroblasts on various barrier membranes was investigated in this study. In this study, human gingival fibroblasts were prepared and cultured on three membranes: collagen membrane, acellular dermal matrix (ADM) with ZnO-NPs, and ADM without ZnO-NPs. WJMSCs-CM was given to the testing groups, while control groups received the same membranes without WJMSCs-CM. Following 48 and 72 h, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) tests were performed to assess cell survival. Cell proliferation on the membranes was also evaluated using 4',6-diamidino-2-phenylindole (DAPI) staining after 48 and 72 h. Field emission scanning electron microscopy was used to determine membrane surface structure and cell adhesion. Nanoparticles were also subjected to an energy-dispersive x-ray analysis to identify their chemical structure. Two-way analysis of variance was used to conduct the statistical analysis. The p-value ≤.05 was considered significant. When ADM-ZnO-NPs were combined with CM, fibroblast viability, and adhesion significantly differed from ADM-ZnO-NPs alone. DAPI results confirmed cell proliferation in all six groups on both experiment days. The abundance and concentrated distribution of cells during cell proliferation were found in CM-containing membranes, specifically the ADM-ZnO-NPs membrane, demonstrating the improved biocompatibility of the ADM-ZnO-NPs membrane for cell proliferation. The other groups did not significantly differ from one another. WJMSCs-CM positively affected the viability and proliferation of gingival fibroblasts, but only marginally. Under certain conditions, ZnO-NPs below a specific concentration increased the biocompatibility of the membranes.

Regeneration Membranes Loaded with Non-Antibiotic Anti-2 Microbials: A Review

Both guided bone and guided tissue regeneration are techniques that require the use of barrier membranes. Contamination and infection of the surgical area is one of the most feared complications. Some current lines of research focus on functionalizing these membranes with different antimicrobial agents. The objective of this study was to carry out a review of the use and antibacterial properties of regeneration membranes doped with antimicrobials such as zinc, silver, chlorhexidine, and lauric acid. The protocol was based on PRISMA recommendations, addressing the PICO question: "Do membranes doped with non-antibiotic antimicrobials have antibacterial activity that can reduce or improve infection compared to membranes not impregnated with said antimicrobial?" Methodological quality was evaluated using the RoBDEMAT tool. A total of 329 articles were found, of which 25 met the eligibility criteria and were included in this review. Most studies agree that zinc inhibits bacterial growth as it decreases colony-forming units, depending on the concentration used and the bacterial species studied. Silver compounds also decreased the secretion of proinflammatory cytokines and presented less bacterial adhesion to the membrane. Some concentrations of chlorhexidine that possess antimicrobial activity have shown high toxicity. Finally, lauric acid shows inhibition of bacterial growth measured by the disk diffusion test, the inhibition zone being larger with higher concentrations. Antimicrobial agents such as zinc, silver, chlorhexidine, and lauric acid have effective antibacterial activity and can be used to dope regenerative membranes in order to reduce the risk of bacterial colonization.

Osseointegration of photodynamic active biomaterials for bone regeneration in an animal bone model over a period of 12 months

OBJECTIVES

Previous efforts led to the development of two different polymeric biomaterials for periodontal regeneration with antibacterial photodynamic surface activity. The present study aimed to investigate osseointegration and bone formation of both materials in an ovine model.

METHODS

Both biomaterials: 1) urethane dimethacrylate-based Biomaterial 1 (BioM1) and 2) tri-armed oligoester-urethane methacrylate-based Biomaterial 2 (BioM2) are enriched with beta-tri-calcium phosphate and the photosensitizer meso-tetra(hydroxyphenyl)chlorin (mTHPC). These materials were implanted in non-critical size bone defects in the sheep femur (n = 16) and tibia (n = 8). Empty defects served as controls (n = 16). Polyfluorochrome sequential bone labeling was carried out at baseline and after 3, 6, and 12 months. Animals were sacrificed after 12 months. Bone specimens (n = 40) were fixed and subjected to microtomographic analysis (µCT) for the evaluation of the bone-volume-fraction (BV/TV), trabecular number and trabecular thickness. Subsequently, histological sections were arranged and polyfluorochrome sequential bone labeling was analyzed by confocal laser scanning microscopy (cLSM).

RESULTS

cLSM analysis revealed that highest remodeling and bone formation activity occurred during the second half of the study period (6-12 months). Bone formation in the tibia was significantly lower for the control (2.71 ± 1.26%) as compared to BioM1 (6.01 ± 2.99%) and BioM2 (6.45 ± 2.12%); (p = 0.006, p = 0004). Micro-computed tomography revealed a BV/TV volume fraction of 44.72 ± 9.01% in femur defects filled with BioM1 which was significantly higher compared to the control (32.27 ± 7.02%; p = 0.01). Bone architecture (trabecular number, trabecular thickness) did not significantly differ from the self-healed defects.

SIGNIFICANCE

Both biomaterials, especially BioM1 showed good osseointegration and bone formation characteristics and can be recommended for further examination in periodontal regeneration studies.

Incorporation of Magnesium and Zinc Metallic Particles in PLGA Bi-layered Membranes with Sequential Ion Release for Guided Bone Regeneration

Guided bone regeneration (GBR) membranes are commonly used for periodontal tissue regeneration. Due to the complications of existing GBR membranes, the design of bioactive membranes is still relevant. GBR membranes with an asymmetric structure can accommodate the functional requirements of different interfacial tissues. Here, poly(lactic acid-glycolic acid) (PLGA) was selected as the matrix for preparing a bi-layered membrane with both dense and porous structure. The dense layer for blocking soft tissues was incorporated with zinc (Zn) particles, while the porous layer for promoting bone regeneration was co-incorporated with magnesium (Mg) and Zn particles. Mg/Zn-embedded PLGA membranes exhibited 166% higher mechanical strength in comparison with pure PLGA membranes and showed suitable degradation properties with a sequential ion release behavior of Mg²⁺ first and continuously Zn²⁺. More importantly, the release of Zn²⁺ from bi-layered PLGA endowed GBR membranes with excellent antibacterial activity (antibacterial rate > 69.3%) as well as good cytocompatibility with MC3T3-E1 (mouse calvaria pre-osteoblastic cells) and HGF-1 (human gingival fibroblast cells). Thus, the asymmetric bi-layered PLGA membranes embedded with Mg and Zn particles provide a simple and effective strategy to not only reinforce the PLGA membrane but also endow membranes with osteogenic and antibacterial activity due to the continuous ion release profile, which serves as a promising candidate for use in GBR therapy.

Doxycycline-doped collagen membranes accelerate in vitro osteoblast proliferation and differentiation

OBJECTIVE

The aim of the study was to evaluate the effect of doxycycline- and dexamethasone-doped collagen membranes on the proliferation and differentiation of osteoblasts.

BACKGROUND

Collagen barrier membranes are frequently used to promote bone regeneration and to boost this biological activity their functionalization with antibacterial and immunomodulatory substances has been suggested.

METHODS

The design included commercially available collagen membranes doped with doxycycline (Dox-Col-M) or dexamethasone (Dex-Col-M), as well as undoped membranes (Col-M) as controls, which were placed in contact with cultured MG63 osteoblast-like cells (ATCC). Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay and differentiation by measuring the alkaline phosphatase (ALP) activity using spectrophotometry. Real-time quantitative polymerase chain reaction was used to study the expression of the genes: Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3. Scanning electron microscopy was used to study osteoblast morphology. Data were assessed using one-way analysis of variance or Kruskal-Wallis tests, once their distribution normality was assessed by Kolmogorov-Smirnov tests (p > .05). Bonferroni for multiple comparisons were carried out (p < .05).

RESULTS

Osteoblast proliferation was significantly enhanced in the functionalized membranes as follows: (Col-M < Dex-Col-M < Dox-Col-M). ALP activity was significantly higher on cultured osteoblasts on Dox-Col-M. Runx-2, OSX, ALP, OSC, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3 were overexpressed, and RANKL was down-regulated in osteoblasts cultured on Dox-Col-M. The osteoblasts cultured in contact with the functionalized membranes demonstrated an elongated spindle-shaped morphology.

CONCLUSION

The functionalization of collagen membranes with Dox promoted an increase in the proliferation and differentiation of osteoblasts.

Coaxial electrospun nanofibers as drug delivery system for local treatment of periodontitis

OBJECTIVES

The aim of the present study was to prepare resorbable polylactide fibers for periodontitis treatment using coaxial electrospinning to optimize the release of metronidazole (MNA) by reducing the initial burst effect.

METHODS

Poly(L-lactide-co-D,L-lactide) (PLA) fibers mats with different distributions of metronidazole (MNA) were manufactured by coaxial electrospinning (COAX). By COAX spinning the central core of the fiber was enriched with 40% MNA (m/m), while the sheath of the fiber consisted of PLA only (test group). In contrast, fibers of the control group were prepared by conventional electrospinning with the same amount of MNA but with a homogenous drug distribution (HDD - homogenously distributed drug). The release of MNA was determined by analyzing aliquots from the fiber mats using UV-VIS spectroscopy. Agar diffusion tests were carried out to determine the antibacterial effect on periodontopathogenic bacteria. Biocompatibility was tested in direct contact to human gingival fibroblasts (HGF) for two days.

RESULTS

The COAX mats showed a retarded drug release compared to the conventional HDD fibers. After 24 h, 64% of total MNA was released cumulatively from the COAX fibers while 90% of the MNA was released from the HDD fibers (controls). The antibacterial effect of COAX fibers was significantly higher after 24 h compared to the HDD fibers. Cell cultivation revealed significant higher numbers of vital cells among the COAX mats.

SIGNIFICANCE

COAX fibers showed improved sustained MNA release compared to conventional fibers and can be seen as potential drug delivery systems in local periodontitis treatment.

Identification of histological threshold concepts in health sciences curricula: Students' perception

Students' metacognitive skills and perceptions are considered important variables for high-quality learning. In this study, students' perceptions were used to identify histological threshold concepts (integrative, irreversible, transformative, and troublesome) in three health sciences curricula. A specific questionnaire was developed and validated to characterize students' perceptions of histological threshold concepts. A sample of 410 undergraduate students enrolled in the dentistry, medicine, and pharmacy degree programs participated in the study. Concepts assessed in the study were clustered to ten categories (factors) by exploratory and confirmatory factor analysis. Concepts linked to tissue organization and tissue functional states received the highest scores from students in all degree programs, suggesting that the process of learning histology requires the integration of both static concepts related to the constituent elements of tissues and dynamic concepts such as stem cells as a tissue renewal substrate, or the euplasic, proplasic and retroplasic states of tissues. The complexity of integrating static and dynamic concepts may pose a challenging barrier to the comprehension of histology. In addition, several differences were detected among the students in different degree programs. Dentistry students more often perceived morphostructural concepts as threshold concepts, whereas medical students highlighted concepts related to two-dimensional microscopic identification. Lastly, pharmacy students identified concepts related to tissue general activity as critical for the comprehension and learning of histology. The identification of threshold concepts through students' perceptions is potentially useful to improve the teaching and learning process in health sciences curricula.

Dexamethasone and Doxycycline Doped Nanoparticles Increase the Differentiation Potential of Human Bone Marrow Stem Cells

Non-resorbable polymeric nanoparticles (NPs) are proposed as an adjunctive treatment for bone regenerative strategies. The present in vitro investigation aimed to evaluate the effect of the different prototypes of bioactive NPs loaded with zinc (Zn-NPs), doxycycline (Dox-NPs) or dexamethasone (Dex-NPs) on the viability, morphology, migration, adhesion, osteoblastic differentiation, and mineralization potential of human bone marrow stem cells (hBMMSCs). Cell viability, proliferation, and differentiation were assessed using a resaruzin-based assay, cell cycle analysis, cell migration evaluation, cell cytoskeleton staining analysis, Alizarin Red S staining, and expression of the osteogenic-related genes by a real-time quantitative polymerase chain reaction (RT-qPCR). One-Way ANOVA and Tukey’s test were employed. The resazurin assay showed adequate cell viability considering all concentrations and types of NPs at 24, 48, and 72 h of culture. The cell cycle analysis revealed a regular cell cycle profile at 0.1, 1, and 10 µg/mL, whereas 100 µg/mL produced an arrest of cells in the S phase. Cells cultured with 0.1 and 1 µg/mL NP concentrations showed a similar migration capacity to the untreated group. After 21 days, mineralization was increased by all the NPs prototypes. Dox-NPs and Dex-NPs produced a generalized up-regulation of the osteogenic-related genes. Dex-NPs and Dox-NPs exhibited excellent osteogenic potential and promoted hBMMSC differentiation. Future investigations, both in vitro and in vivo, are required to confirm the suitability of these NPs for their clinical application.

Antibiotic-Loaded Polymeric Barrier Membranes for Guided Bone/Tissue Regeneration: A Mini-Review

Polymeric membranes are frequently used for bone regeneration in oral and periodontal surgery. Polymers provide adequate mechanical properties (i.e., Young’s modulus) to support oral function and also pose some porosity with interconnectivity to permit for cell proliferation and migration. Bacterial contamination of the membrane is an event that may lead to infection at the bone site, hindering the clinical outcomes of the regeneration procedure. Therefore, polymeric membranes have been proposed as carriers for local antibiotic therapy. A literature search was performed for papers, including peer-reviewed publications. Among the different membranes, collagen is the most employed biomaterial. Collagen membranes and expanded polytetrafluoroethylene loaded with tetracyclines, and polycaprolactone with metronidazole are the combinations that have been assayed the most. Antibiotic liberation is produced in two phases. A first burst release is sometimes followed by a sustained liberation lasting from 7 to 28 days. All tested combinations of membranes and antibiotics provoke an antibacterial effect, but most of the time, they were measured against single bacteria cultures and usually non-specific pathogenic bacteria were employed, limiting the clinical relevance of the attained results. The majority of the studies on animal models state a beneficial effect of these antibiotic functionalized membranes, but human clinical assays are scarce and controversial.

Finding the Perfect Membrane: Current Knowledge on Barrier Membranes in Regenerative Procedures: A Descriptive Review

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) became common procedures in the corrective phase of periodontal treatment. In order to obtain good quality tissue neo-formation, most techniques require the use of a membrane that will act as a barrier, having as a main purpose the blocking of cell invasion from the gingival epithelium and connective tissue into the newly formed bone structure. Different techniques and materials have been developed, aiming to obtain the perfect barrier membrane. The membranes can be divided according to the biodegradability of the base material into absorbable membranes and non-absorbable membranes. The use of absorbable membranes is extremely widespread due to their advantages, but in clinical situations of significant tissue loss, the use of non-absorbable membranes is often still preferred. This descriptive review presents a synthesis of the types of barrier membranes available and their characteristics, as well as future trends in the development of barrier membranes along with some allergological aspects of membrane use.

Finding the Perfect Membrane: Current Knowledge on Barrier Membranes in Regenerative Procedures: A Descriptive Review

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) became common procedures in the corrective phase of periodontal treatment. In order to obtain good quality tissue neo-formation, most techniques require the use of a membrane that will act as a barrier, having as a main purpose the blocking of cell invasion from the gingival epithelium and connective tissue into the newly formed bone structure. Different techniques and materials have been developed, aiming to obtain the perfect barrier membrane. The membranes can be divided according to the biodegradability of the base material into absorbable membranes and non-absorbable membranes. The use of absorbable membranes is extremely widespread due to their advantages, but in clinical situations of significant tissue loss, the use of non-absorbable membranes is often still preferred. This descriptive review presents a synthesis of the types of barrier membranes available and their characteristics, as well as future trends in the development of barrier membranes along with some allergological aspects of membrane use.

Antibacterial Effect of Functionalized Polymeric Nanoparticles on Titanium Surfaces Using an In Vitro Subgingival Biofilm Model

This investigation aimed to evaluate the antibacterial effect of polymeric nanoparticles (NPs), functionalized with calcium, zinc, or doxycycline, using a subgingival biofilm model of six bacterial species (Streptococcus oralis,Actinomyces naeslundii, Veillonela parvula, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans) on sandblasted, large grit, acid-etched titanium discs (TiDs). Undoped NPs (Un-NPs) or doped NPs with calcium (Ca-NPs), zinc (Zn-NPs), or doxycycline (Dox-NPs) were applied onto the TiD surfaces. Uncovered TiDs were used as negative controls. Discs were incubated under anaerobic conditions for 12, 24, 48, and 72 h. The obtained biofilm structure was studied by scanning electron microscopy (SEM) and its vitality and thickness by confocal laser scanning microscopy (CLSM). Quantitative polymerase chain reaction of samples was used to evaluate the bacterial load. Data were evaluated by analysis of variance (p < 0.05) and post hoc comparisons with Bonferroni adjustments (p < 0.01). As compared with uncovered TiDs, Dox-NPs induced higher biofilm mortality (47.21% and 85.87%, respectively) and reduced the bacterial load of the tested species, after 72 h. With SEM, scarce biofilm formation was observed in Dox-NPs TiDs. In summary, Dox-NPs on TiD reduced biofilm vitality, bacterial load, and altered biofilm formation dynamics.

Zn-Containing Membranes for Guided Bone Regeneration in Dentistry

Barrier membranes are employed in guided bone regeneration (GBR) to facilitate bone in-growth. A bioactive and biomimetic Zn-doped membrane with the ability to participate in bone healing and regeneration is necessary. The aim of the present study is to state the effect of doping the membranes for GBR with zinc compounds in the improvement of bone regeneration. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken, focusing on the antibacterial effects, physicochemical and biological properties of Zn-loaded membranes. Bioactivity, bone formation and cytotoxicity were analyzed. Microstructure and mechanical properties of these membranes were also determined. Zn-doped membranes have inhibited in vivo and in vitro bacterial colonization. Zn-alloy and Zn-doped membranes attained good biocompatibility and were found to be non-toxic to cells. The Zn-doped matrices showed feasible mechanical properties, such as flexibility, strength, complex modulus and tan delta. Zn incorporation in polymeric membranes provided the highest regenerative efficiency for bone healing in experimental animals, potentiating osteogenesis, angiogenesis, biological activity and a balanced remodeling. Zn-loaded membranes doped with SiO₂ nanoparticles have performed as bioactive modulators provoking an M2 macrophage increase and are a potential biomaterial for promoting bone repair. Zn-doped membranes have promoted pro-healing phenotypes.

Doxycycline-doped membranes induced osteogenic gene expression on osteoblastic cells

OBJECTIVES

To analyze how novel developed silicon dioxide composite membranes, functionalized with zinc or doxycycline, can modulate the expression of genes related to the osteogenic functional capacity of osteoblastic cells.

METHODS

The composite nanofibers membranes were manufactured by using a novel polymeric blend and 20 nm silicon dioxide nanoparticles (SiO₂-NPs). To manufacture the membranes, 20 nm SiO₂-NPs were added to the polymer solution and the resulting suspension was processed by electrospinning. In a second step, the membranes were functionalized with zinc or doxycycline. Then, they were subjected to MG63 osteoblast-like cells culturing for 48 h. After this time, real-time quantitative polymerase chain reaction (RT-qPCR) was carried out to study the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF- βR2, and TGF-βR3. Mean comparisons were conducted by One-way ANOVA and Tukey tests (p < 0.05).

RESULTS

In general, the blending of SiO₂-NPs in the tested non-resorbable polymeric scaffold improves the expression of osteogenic genes over the control membranes. Doxycycline doping of experimental scaffolds attained the best results, encountering up-regulation of BMP-2, ALP, OPG, TGFβ-1 and TGFβ-R1. Membranes with zinc induced a significant increase in the expression of Col-I, ALP and TGF β1. Both, zinc and doxycycline functionalized membranes enormously down-regulated the expression of RANKL.

CONCLUSIONS

Zinc and doxycycline doped membranes are bioactive inducing overexpression of several osteogenic gene markers.

CLINICAL SIGNIFICANCE

Doxycycline doped membranes may be a potential candidate for use in GBR procedures in several challenging pathologies, including periodontal diseases.

Alveolar Bone Ridge Augmentation Using Polymeric Membranes: A Systematic Review and Meta-Analysis

Alveolar bone ridge resorption occurred after natural teeth loss and it can restrict the possibility of dental implants placement. The use of bone regenerative procedures is frequently required. The existing evidence regarding the efficacy of horizontal bone ridge augmentation trough guided bone regeneration (GBR) using polymeric membranes was stated. A systematic review and meta-analysis were performed. Electronic and manual literature searches were conducted. Screening process was done using the National Library of Medicine (MEDLINE by PubMed), Embase, and the Cochrane Oral Health. Included articles were randomized controlled trials and observational studies. Weighted means were calculated. Heterogeneity was determined using Higgins (I2). If I2 > 50% a random-effects model was applied. It was found that the mean of horizontal bone gain was 3.95 mm, ranging from 3.19 to 4.70 mm (confidence interval 95%). Heterogeneity is I2 = 99% (confidence interval 95%) and significance of the random-effects model was p < 0.001. The complications rate was 8.4% and membrane exposure was the most frequent. Through this study, we were able to conclude that the existing scientific evidence suggests that GBR using polymeric membranes is a predictable technique for achieving horizontal bone augmentation, thus, permitting a proper further implant placement.

Doxycycline-Doped Polymeric Membranes Induced Growth, Differentiation and Expression of Antigenic Phenotype Markers of Osteoblasts

Polymeric membranes are employed in guided bone regeneration (GBR) as physical barriers to facilitate bone in-growth. A bioactive and biomimetic membrane with the ability to participate in the healing and regeneration of the bone is necessary. The aim of the present study was to analyze how novel silicon dioxide composite membranes functionalized with zinc or doxycycline can modulate the osteoblasts' proliferation, differentiation, and expression of selected antigenic markers related to immunomodulation. Nanostructured acrylate-based membranes were developed, blended with silica, and functionalized with zinc or doxycycline. They were subjected to MG63 osteoblast-like cells culturing. Proliferation was assessed by MTT-assay, differentiation by evaluating the alkaline phosphatase activity by a spectrophotometric method and antigenic phenotype was assessed by flow cytometry for selected markers. Mean comparisons were conducted by one-way ANOVA and Tukey tests (p < 0.05). The blending of silica nanoparticles in the tested non-resorbable polymeric scaffold improved the proliferation and differentiation of osteoblasts, but doxycycline doped scaffolds attained the best results. Osteoblasts cultured on doxycycline functionalized membranes presented higher expression of CD54, CD80, CD86, and HLA-DR, indicating a beneficial immunomodulation activity. Doxycycline doped membranes may be a potential candidate for use in GBR procedures in several challenging pathologies, including periodontal disease.

Relevance of Biofilm Models in Periodontal Research: From Static to Dynamic Systems

Microbial biofilm modeling has improved in sophistication and scope, although only a limited number of standardized protocols are available. This review presents an example of a biofilm model, along with its evolution and application in studying periodontal and peri-implant diseases. In 2011, the ETEP (Etiology and Therapy of Periodontal and Peri-Implant Diseases) research group at the University Complutense of Madrid developed an in vitro biofilm static model using representative bacteria from the subgingival microbiota, demonstrating a pattern of bacterial colonization and maturation similar to in vivo subgingival biofilms. When the model and its methodology were standardized, the ETEP research group employed the validated in vitro biofilm model for testing in different applications. The evolution of this model is described in this manuscript, from the mere observation of biofilm growth and maturation on static models on hydroxyapatite or titanium discs, to the evaluation of the impact of dental implant surface composition and micro-structure using the dynamic biofilm model. This evolution was based on reproducing the ideal microenvironmental conditions for bacterial growth within a bioreactor and reaching the target surfaces using the fluid dynamics mimicking the salivary flow. The development of this relevant biofilm model has become a powerful tool to study the essential processes that regulate the formation and maturation of these important microbial communities, as well as their behavior when exposed to different antimicrobial compounds.

Testing active membranes for bone regeneration: A review

OBJECTIVES

Maxillofacial bone defects are the main hindering conditions for traditional dental implant strategies. Guided Bone Regeneration (GBR) is used to handle this situation. The principle of GBR is to use a membrane to prevent the colonization of soft tissue cells of the bone defect and favors the migration of osteogenic linages. Current membranes do not completely fulfill the requirements that an optimal membrane should have, sometimes resulting in non-predictable results. Thus, the need to develop an ideal membrane to perform this duty is clear. Recent developments in bio-manufacturing are driving innovations in membranes technology permitting the active participation of the membrane in the healing and regenerative process trough native tissue mimicking, drug-delivery and cells interaction, away from being a passive barrier. New membranes features need specific evaluation techniques, beyond the International Standard for membrane materials (last reviewed in 2004), being this the rationale for the present review. Nanotechnology application has completely shifted the way of analyzing structural characterization. New progresses on osteoimmmunomodulation have also switched the understanding of cells-membranes interaction.

DATA AND SOURCES

To propose an updated protocol for GBR membranes evaluation, critical reading of the relevant published literature was carried out after a MEDLINE/PubMed database search.

CONCLUSIONS

The main findings are that a potential active membrane should be assessed in its nanostructure, physicochemical and nanomechanical properties, bioactivity and antibacterial, osteoblasts proliferation, differentiation and mineralization. Immunomodulation testing for macrophages recruitment and M2 phenotype promotion in osteoblasts co-culture has to be achieved to completely analyze membranes/tissue interactions.

Protein adsorption and bioactivity of functionalized electrospun membranes for bone regeneration

OBJECTIVES

To evaluate the adsorption of bone related proteins and bioactivity of experimental functionalized (carboxylated or aminated) polymeric membranes for bone regeneration.

METHODS

Polymethylmethacrylate-based membranes functionalized with carboxyl or amino radicals were tested. Membranes were zinc loaded and the adsorption isotherms of zinc were studied. Human plasma proteins, bovine serum albumin, fibrinogen and fibronectin adsorption were measured with a spectrophotometer applying an acid determination protocol. Biomimetic calcium phosphate precipitation on polymeric membranes was also assessed after simulated body fluid immersion. Scanning electron microscopy and elemental analysis by means of an energy dispersive system were used for mineral deposits identification. A commercially available polytetrafluoroethylene membrane was used as control.

RESULTS

Both experimental membranes produced higher protein adsorption than the commercial control that does not adsorb proteins. Carboxylated membranes adsorbed significantly more albumin than the aminated ones, the opposite occurred with fibrinogen. With plasma and fibronectin proteins both type of membranes performed similarly. Only carboxylated membranes were bioactive and precipitated calcium and phosphate on their surfaces.

CONCLUSIONS

The polymethylmethacrylate zinc-loaded membranes functionalized with carboxyl groups performed as high adsorbable membranes for bone regeneration related proteins. They also served as templates for mineralization of hydroxyapatite.

CLINICAL SIGNIFICANCE

Protein adsorption is the initial reaction after the implantation of a biomaterial into the body and will influence subsequent cell function. The adsorption of bone related proteins together with the observed biomimetic calcium deposition on the experimental carboxylated membranes could be associated with their ability to promote bone regeneration.