Occlusive membranes for guided regeneration of inflamed tissue defects

Biodegradable Piezoelectric Janus Membrane with Enhanced Antibacterial and Osteoinductive Properties for Periodontitis Therapy

An ideal guided bone regeneration (GBR) membrane for periodontitis treatment should incorporate biocompatibility, biodegradability, mechanical strength, antibacterial properties, and osteoconductivity. However, no commercially available GBR membrane meets all these criteria simultaneously. In this study, a novel biodegradable piezoelectric double-layered membrane is developed, with a non-piezoelectric Poly-L-lactic acid (PLLA) side facing the gingiva and a piezoelectric PLLA-ZnO side facing the alveolar bone. This asymmetric GBR membrane, with distinct fiber orientations and charge distribution, combines and synergizes mechanical strength, degradability, barrier function, antibacterial activity and osteogenic potential to enhance bone regeneration efficacy. The GBR membrane can effectively prevent fibroblast migration, inhibits bacterial infection, and promotes bone regeneration both in vitro and in vivo. In vitro testing shows good antibacterial rate against Porphyromonas gingivalis (P. gingivalis) and Staphylococcus aureus (S. aureus) after 10 min of ultrasound stimulation. Expression levels of osteogenic genes Bone morphogenetic Protein 2 (BMP2), Runt-related transcription factor 2 (RUNX2), Osteopontin (OPN) and Osteocalcin (OCN) are over twice that of the control. In a mouse P. gingivalis-mediated periodontitis model, our composite membrane demonstrates effective antimicrobial effects and promote bone regeneration after 2- and 4-weeks implantation, facilitated by mechanisms such as physical isolation, zinc ion release, piezoelectric effects, enhanced expression of osteogenic genes through activation of osteogenesis-related signaling pathways, underscoring its strong potential for GBR applications.

Biological and mechanical challenges in the endodontic treatment of immature teeth with pulp necrosis: insights based on a Series of Atypical Clinical Cases

Over the past two decades, dental pulp regeneration has become a major focus in endodontology. The currently applied clinical strategies are referred to as 'revitalisation' procedures. These biology-based treatment strategies aim at regenerating lost pulp tissues in necrotic teeth, in the absence or even more in the presence of periapical bone lesion, clinical signs and symptoms. Such approaches are generally - but not exclusively - used in immature teeth to promote root maturation, both in length and in thickness, ultimately to reduce their risk of fracture. A growing body of evidence has led to increased understanding and reliability of these treatment strategies, which are now considered as a valid alternative treatment option besides conventional ones, mainly the apical plug technique. However, all systematic reviews evaluating clinical outcomes concluded that there is a lack of robust long-term studies on the subject; most published cases of revitalisation having a relatively short-term follow-up, usually under 2 years. In this context, several major challenges remain to be addressed to better understand the promises and limitations of revitalisation procedures as compared to other treatment options, mainly the placement of an apical plug made of hydraulic calcium silicate cement. The purpose of this paper was therefore to identify some of the important remaining challenges related to such procedures, which can be broadly categorised into biological and mechanical ones, affecting treatment success and tooth survival. Meeting these challenges requires close collaboration between both researchers and clinicians, to establish guidelines, evaluate and understand treatment outcomes, and update guidelines accordingly. However, it is not always easy for researchers to understand the clinical reality faced by practitioners. In order to facilitate their mutual understanding, the aforementioned challenges were illustrated by providing clinical context through a series of atypical clinical cases with long-term follow-up (4-8 years).

Regulation of the gelatin helix-to-coil transition through chain confinements at the polymer-protein interface and protein-protein interface

Gelatin is an essential material widely used in biomedical applications due to its characteristic temperature responsivity-helix-to-coil transition. However, the current helix-to-coil transition is limited by its single-step behavior and the difficulty in designing a specific onset temperature. In this study, we investigated the fundamentals of the helix-to-coil transition with a focus on gelatin chain mobility. We observed distinctive kinetics of the helix-to-coil transition, which is resilient and can actuate in multiple steps or with a controllable onset point. This was achieved by confining the gelatin chain with a hydrophilic polymer or gelatin itself. The confinement approach serves two purposes: first, it prevents excessive mobility of the generated coils, maintaining physical resilience after the helix-to-coil transition; second, the interfacial confinement between the polymer and gelatin, referred to as polymer-protein interface confinement, restricts the helix-to-coil transition, resulting in a multistep transition process. Additionally, strong confinement at the interface between gelatins of different origins, that is protein-protein interface confinement, shifts the onset temperature to a higher point. This fundamental comprehension of helix-to-coil transition could contribute to broadening the biomedical application potential of gelatin materials. STATEMENT OF SIGNIFICANCE: Gelatin is essential in biomedical applications due to its characteristic temperature responsivity-helix-to-coil transition. Herein, we fundamentally investigated the distinctive kinetics of the helix-to-coil transition, which is resilient and can actuate in multiple steps or with a controllable onset point. This was achieved by confining the gelatin chain with a hydrophilic polymer or gelatin itself. The gelatin chain confinement prevents excessive mobility of the generated coils, maintaining physical resilience after the helix-to-coil transition. The interfacial confinement between the polymer and gelatin restricts the helix-to-coil transition, resulting in a multistep transition process. Additionally, strong confinement at the interface between gelatins of different origins shifts the onset temperature to a higher point.

Evaluation of toxicity, local biocompatibility, biodegradation, and systemic metabolism of cellulose/alginate/strontium apatite membranes implanted subcutaneously in mice

PURPOSE

To evaluate membranes originating from pure or oxidized bacterial cellulose (BC)/alginate/strontium apatite hydrogels regarding toxicity, biocompatibility, biodegradation and metabolism.

METHODS

The toxicity was measured by incubating the materials with Artemia salina for 24 h, and mortality and the 50% lethal concentration were determined in comparison to potassium dichromate by Probit analysis. Local biocompatibility and biodegradation were evaluated by subcutaneous assay in 75 Swiss mice; the test groups were compared to sham and collagen membrane at one, three and nine weeks. The histopathology of tissue irritation followed the ISO 10993-6 standard, and the integrity of the biomaterials scored by quartiles. Metabolic analysis of relative weight and the intensity of catalase, iodine and nitrite were carried out for liver, kidneys and tibias of the tested animals.

RESULTS

All cellulose-based materials were nontoxic, biocompatible, and none presented nitrosative stress. The oxidized BC was more resorbable, and the non-oxidized BC had greater renal biochemical reactivity.

CONCLUSION

The membranes suggest applicability as regenerative barriers. However, long-term studies in bone defects are necessary to elucidate their osteopromoting efficiency.

Viscoelastic and antimicrobial dental care bioplastic with recyclable life cycle

Medical plastic-appliance-based healthcare services, especially in dentistry, generate tremendous amounts of plastic waste. Given the physiological features of our mouth, it is desirable to substitute dental care plastics with viscoelastic and antimicrobial bioplastics. Herein, we develop a medical-grade and sustainable bioplastic that is viscoelastic enough to align the tooth positions, resists microbial contamination, and exhibits recyclable life cycles. In particular, we devise a molecular template involving entanglement-inducing and antimicrobial groups and prepare a silk fibroin-based dental care bioplastic. The generated compactly entangled structure endows great flexibility, toughness, and viscoelasticity. Therefore, a satisfactory orthodontic outcome is accomplished, as demonstrated by the progressive alignment of male rabbit incisors within the 2.5 mm range. Moreover, the prepared bioplastic exhibits resistance to pathogenic colonization of intraoral microbes such as Streptococcaceae and Veillonellaceae. Because the disentanglement of entangled domains enables selective separation and extraction of the components, the bioplastic can be recycled into a mechanically identical one. The proposed medical-grade and sustainable bioplastic could potentially contribute to a green healthcare future.

Polyphenol-mediated redox-active hydrogel with H2S gaseous-bioelectric coupling for periodontal bone healing in diabetes

Excessive oxidative response, unbalanced immunomodulation, and impaired mesenchymal stem cell function in periodontitis in diabetes makes it a great challenge to achieve integrated periodontal tissue regeneration. Here, a polyphenol-mediated redox-active algin/gelatin hydrogel encapsulating a conductive poly(3,4-ethylenedioxythiopene)-assembled polydopamine-mediated silk microfiber network and a hydrogen sulfide sustained-release system utilizing bovine serum albumin nanoparticles is developed. This hydrogel is found to reverse the hyperglycemic inflammatory microenvironment and enhance functional tissue regeneration in diabetic periodontitis. Polydopamine confers the hydrogel with anti-oxidative and anti-inflammatory activity. The slow, sustained release of hydrogen sulfide from the bovine serum albumin nanoparticles recruits mesenchymal stem cells and promotes subsequent angiogenesis and osteogenesis. Moreover, poly(3,4-ethylenedioxythiopene)-assembled polydopamine-mediated silk microfiber confers the hydrogel with good conductivity, which enables it to transmit endogenous bioelectricity, promote cell arrangement, and increase the inflow of calcium ion. In addition, the synergistic effects of hydrogen sulfide gaseous-bioelectric coupling promotes bone formation by amplifying autophagy in periodontal ligament stem cells and modulating macrophage polarization via lipid metabolism regulation. This study provides innovative insights into the synergistic effects of conductivity, reactive oxygen species scavenging, and hydrogen sulfide on the periodontium in a hyperglycemic inflammatory microenvironment, offering a strategy for the design of gaseous-bioelectric biomaterials to promote functional tissue regeneration in immune-related diseases.

Bioinspired triple-layered membranes for periodontal guided bone regeneration applications

Barrier membranes have been used for the treatment of alveolar bone loss caused by periodontal diseases or trauma. However, an optimal barrier membrane must satisfy multiple requirements simultaneously, which are challenging to combine into a single material. We herein report the design of a bioinspired membrane consisting of three functional layers. The primary layer is composed of clay nanosheets and chitin, which form a nacre-inspired laminated structure. A calcium phosphate mineral layer is deposited on the inner surface of the nacre-inspired layer, while a poly(lactic acid) layer is coated on the outer surface. The composite membrane integrates good mechanical strength and deformability because of the nacre-inspired structure, facilitating operations during the implant surgery. The mineral layer induces the osteogenic differentiation of bone marrow mesenchymal stem cells and increases the stiffness of the membrane, which is an important factor for the regeneration process. The poly(lactic acid) layer can prevent unwanted mineralization on the outer surface of the membrane in oral environments. Cell experiments reveal that the membrane exhibits good biocompatibility and anti-infiltration capability toward connective tissue/epithelium cells. Furthermore, in vitro analyses show that the membrane does not degrade too fast, allowing enough time for bone regeneration. In vivo experiments prove that the membrane can effectively induce better bone regeneration and higher trabecular bone density in alveolar bone defects. This study demonstrates the potential of this bioinspired triple-layered membrane with hierarchical structures as a promising barrier material for periodontal guided tissue regeneration.

Immune checkpoint regulation is critically involved in canine cutaneous histiocytoma regression

Introduction

Canine cutaneous histiocytoma (CCH) is a benign tumor frequently occurring in young dogs which is derived from Langerhans cells (LC). Distinguishing features of this tumor are its spontaneous regression following a rapid tumor growth. Impaired control of immune checkpoints during tumor development and progression is a widespread phenomenon which may result in an absent or ineffective immune response. The interaction between the inflammatory response and the expression of immune checkpoint molecules is only partially described in this tumor type. The aim of this study was to identify immune checkpoint molecules and molecules from the interferon-mediated immune response that are involved in the regression of CCH.

Methods

Forty-eight CCH derived from dogs ≤ 4 years of age were assigned to one of four groups according to the severity and distribution of lymphocyte infiltration. Using immunohistochemistry and whole-slide image scans of consecutive sections the expression of programmed death protein ligand 1 (PD-L1), CD80, CD86, Survivin, forkhead box protein 3, Ki-67, cleaved caspase-3, CD3, and mx1 were investigated. RNA in-situ hybridization was performed for transcripts of mx1 and interferon-γ.

Results

Neoplastic cells showed an expression of PD-L1, CD80, CD86, and Survivin. The density of CD80 expressing cells was negatively correlated with regression while the density of cleaved caspase-3 positive cells increased with regression. Mx1 transcripts and protein were predominantly localized in neoplastic cells while interferon-γ transcripts were most frequently detected in T-cells.

Conclusion

The expression of the immune checkpoint molecules CD86 and PD-L1 and particularly the reduced expression of CD80 in groups 3 and 4 indicate an influence of the investigated immune checkpoints on tumor regression. In parallel an activation of the apoptotic cascade during regression is suggested. Finally, the detection of mx1 within the neoplasm pinpoints to a yet undisclosed role of anti-cellular signaling in tumor immunity.

Anisotropic Liesegang pattern for the nonlinear elastic biomineral-hydrogel complex

The Liesegang pattern is a beautiful natural anisotropic patterning phenomenon observed in rocks and sandstones. This study reveals that the Liesegang pattern can induce nonlinear elasticity. Here, a Liesegang-patterned complex with biomineral-hydrogel repetitive layers is prepared. This Liesegang-patterned complex is obtained only when the biomineralization is performed under the supersaturated conditions. The Liesegang-patterned complex features a nonlinear elastic response, whereas a complex with a single biomineral shell shows a linear behavior, thus demonstrating that the Liesegang pattern is essential in achieving nonlinear elasticity. The stiff biomineral layers have buffered the concentrated energy on behalf of soft hydrogels, thereby exposing the hydrogel components to reduced stress and, in turn, enabling them to perform the elasticity continuously. Moreover, the nonlinear elastic Liesegang-patterned complex exhibits excellent stress relaxation to the external loading, which is the biomechanical characteristic of cartilage. This stress relaxation allows the bundle of fiber-type Liesegang-patterned complex to endure greater deformation.

Evaluation of the antibacterial effect of Epigallocatechin gallate on the major pathogens of canine periodontal disease and therapeutic effects on periodontal disease mice

Background

Periodontal disease (PD) is a prevalent oral affliction in canines, with limited therapeutic options available. The potential transmission of oral bacteria from canines to humans through inter-species contact poses a risk of zoonotic infection. Epigallocatechin gallate (EGCG), the principal catechin in green tea polyphenols, exhibits antibacterial properties effective against human PD. Given the clinical parallels between canine and human PD, this study explores the feasibility of employing EGCG as a therapeutic agent for canine PD.

Methods and results

Initially, a survey and statistical analysis of bacterial infection data related to canine PD in China were conducted. Subsequently, the primary pathogenic bacteria of canine PD were isolated and cultivated, and the in vitro antibacterial efficacy of EGCG was assessed. Furthermore, verify the therapeutic effect of EGCG on a mouse PD model in vivo. The high-throughput 16S rRNA gene sequencing identified Porphyromonas, Fusobacterium, Treponema, Moraxella, and Capnocytophaga as the genera that distinguishing PD from healthy canines' gingival crevicular fluid (GCF) samples in China. The anaerobic culture and drug susceptibility testing isolated a total of 92 clinical strains, representing 22 species, from 72 canine GCF samples, including Porphyromonas gulae, Prevotella intermedia, Porphyromonas macacae, etc. The minimum inhibitory concentration (MIC) ranging of EGCG was from 0.019 to 1.25 mg/mL. Following a 7 days oral mucosal administration of medium-dose EGCG (0.625 mg/mL), the abundance of periodontal microorganisms in PD mice significantly decreased. This intervention ameliorated alveolar bone loss, reducing the average cementoenamel junction to the alveolar bone crest (CEJ-ABC) distance from 0.306 mm ± 0.050 mm to 0.161 mm ± 0.026 mm. Additionally, EGCG (0.3125 mg/mL) markedly down-regulated the expression of inflammatory factor IL-6 in the serum of PD mice.

Conclusion

Our research demonstrates the significant antibacterial effects of EGCG against the prevalent bacterium P. gulae in canine PD. Moreover, EGCG exhibits anti-inflammatory properties and proves effective in addressing bone loss in a PD mouse model. These findings collectively suggest the therapeutic potential of EGCG in the treatment of canine PD. The outcomes of this study contribute valuable data, laying the foundation for further exploration and screening of alternative antibiotic drugs to advance the management of canine PD.