Biomimetic, mussel-inspired surface modification of 3D-printed biodegradable polylactic acid scaffolds with nano-hydroxyapatite for bone tissue engineering.

Polylactic acid (PLA) has been widely used as filaments for material extrusion additive manufacturing (AM) to develop patient-specific scaffolds in bone tissue engineering. Hydroxyapatite (HA), a major component of natural bone, has been extensively recognized as an osteoconductive biomolecule. Here, inspired by the mussel-adhesive phenomenon, in this study, polydopamine (PDA) coating was applied to the surface of 3D printed PLA scaffolds (PLA@PDA), acting as a versatile adhesive platform for immobilizing HA nanoparticles (nHA). Comprehensive analyses were performed to understand the physicochemical properties of the 3D-printed PLA scaffold functionalized with nHA and PDA for their potent clinical application as a bone regenerative substitute. Scanning electron microscopy (SEM) and element dispersive X-ray (EDX) confirmed a successful loading of nHA particles on the surface of PLA@PDA after 3 and 7 days of coating (PLA@PDA-HA3 and PLA@PDA-HA7), while the surface micromorphology and porosity remain unchanged after surface modification. The thermogravimetric analysis (TGA) showed that 7.7 % and 12.3% mass ratio of nHA were loaded on the PLA scaffold surface, respectively. The wettability test indicated that the hydrophilicity of nHA-coated scaffolds was greatly enhanced, while the mechanical properties remained uncompromised. The 3D laser scanning confocal microscope (3DLS) images revealed that the surface roughness was significantly increased, reaching Sa (arithmetic mean height) of 0.402 µm in PLA@PDA-HA7. Twenty-eight days of in-vitro degradation results showed that the introduction of nHA to the PLA surface enhances its degradation properties, as evidenced by the SEM images and weight loss test. Furthermore, a sustainable release of Ca2+ from PLA@PDA-HA3 and PLA@PDA-HA7 was recorded, during the degradation process. In contrast, the released hydroxyl group of nHA tends to neutralize the local acidic environments, which was more conducive to osteoblastic differentiation and extracellular mineralization. Taken together, this facile surface modification provides 3D printed PLA scaffolds with effective bone regenerative properties by depositing Ca2+ contents, improving surface hydrophilicity, and enhancing the in-vitro degradation rate.

FOXO1 Mediates Advanced Glycation End Products Induced Mouse Osteocyte-Like MLO-Y4 Cell Apoptosis and Dysfunctions.

Osteocyte plays an essential role in bone metabolism by regulating osteoblast and osteoclast activities. Dysfunction or apoptosis of osteocyte will severely endanger the bone homeostasis and result in bone diseases such as osteoporosis. Osteoporosis has been considered as one of the diabetes complications; however, the mechanism is still to be discovered. Advanced glycation end products (AGEs), as the main pathogenic factor of diabetes mellitus, have the capacity to induce osteocyte apoptosis thus sabotaging bone homeostasis. Here, we examined the role of AGE during osteocyte apoptosis and how this effect would affect osteocyte's regulation of osteoblast and osteoclast. Mouse osteocyte-like MLO-Y4 cells were used to study the properties of osteocyte and to examine its biological and pathological function. MTT assay and Annexin V assay showed that AGE significantly induce MLO-Y4 cell apoptosis. qPCR and Western blot results have shown that AGE upregulates proapoptotic gene p53 and its downstream target gene Bax, which leads to enhanced activation of caspase-3, thus inducing apoptosis in MLO-Y4 cells. Increased expression of sclerostin and RANKL in osteocytes has shown that AGE induces osteocyte dysfunction thus severely damaging the bone homeostasis by decreasing osteoblast and increasing osteoclast activities. Furthermore, the role of the transcription factor FOXO1, which is intensely associated with apoptosis, has been determined. Western blot has shown that AGE significantly decreases Akt activities. Immunofluorescence has shown that AGE promotes FOXO1 nuclei localization and enhances FOXO1 expression. Silencing of FOXO1 suppressed AGE-enhanced apoptosis; mRNA and protein expressions of cleaved caspase-3, sclerostin, and RANKL were downregulated as well. Moreover, exogenous FOXO1 increased caspase-3 mRNA levels and caspase-3 transcriptional activity. Lastly, ChIP assay has established the capacity of FOXO1 binding directly on the caspase-3, sclerostin, and RANKL promoter region in AGE environment, providing the mechanism of the AGE-induced osteocyte apoptosis and dysfunction. Our results have shown that FOXO1 plays a crucial role in AGE-induced osteocyte dysfunction and apoptosis through its regulation of caspase-3, sclerostin, and RANKL. This study provides new insight into diabetes-enhanced risk of osteoporosis given the critical role of AGE in the pathogenesis of diabetes and the essential part of osteocyte in bone metabolism.

Novel nanomaterial-based antibacterial photodynamic therapies to combat oral bacterial biofilms and infectious diseases.

Oral diseases such as tooth caries, periodontal diseases, endodontic infections, etc., are prevalent worldwide. The heavy burden of oral infectious diseases and their consequences on the patients' quality of life indicates a strong need for developing effective therapies. Advanced understandings of such oral diseases, e.g., inflammatory periodontal lesions, have raised the demand for antibacterial therapeutic strategies, because these diseases are caused by viruses and bacteria. The application of antimicrobial photodynamic therapy (aPDT) on oral infectious diseases has attracted tremendous interest in the past decade. However, aPDT had a minimal effect on the viability of organized biofilms due to the hydrophobic nature of the majority of the photosensitizers (PSs). Therefore, novel nanotechnologies were rapidly developed to target the delivery of hydrophobic PSs into microorganisms for the antimicrobial performance improvement of aPDT. This review focuses on the state-of-the-art of nanomaterials applications in aPDT against oral infectious diseases. The first part of this article focuses on the cutting-edge research on the synthesis, toxicity, and therapeutic effects of various forms of nanomaterials serving as PS carriers for aPDT applications. The second part discusses nanomaterials applications for aPDT in treatments of oral diseases. These novel bioactive nanomaterials have demonstrated great potential to serve as carriers for PSs to substantially enhance the PDT therapeutic effects. Furthermore, the novel aPDT applications not only have exciting therapeutic potential to inhibit bacterial plaque-initiated oral diseases, but also have a wide applicability to other biomedical and tissue engineering applications.

Novel Bioactive and Therapeutic Dental Polymeric Materials to Inhibit Periodontal Pathogens and Biofilms.

Periodontitis is a common infectious disease characterized by loss of tooth-supporting structures, which eventually leads to tooth loss. The heavy burden of periodontal disease and its negative consequence on the patient's quality of life indicate a strong need for developing effective therapies. According to the World Health Organization, 10⁻15% of the global population suffers from severe periodontitis. Advances in understanding the etiology, epidemiology and microbiology of periodontal pocket flora have called for antibacterial therapeutic strategies for periodontitis treatment. Currently, antimicrobial strategies combining with polymer science have attracted tremendous interest in the last decade. This review focuses on the state of the art of antibacterial polymer application against periodontal pathogens and biofilms. The first part focuses on the different polymeric materials serving as antibacterial agents, drug carriers and periodontal barrier membranes to inhibit periodontal pathogens. The second part reviews cutting-edge research on the synthesis and evaluation of a new generation of bioactive dental polymers for Class-V restorations with therapeutic effects. They possess antibacterial, acid-reduction, protein-repellent, and remineralization capabilities. In addition, the antibacterial photodynamic therapy with polymeric materials against periodontal pathogens and biofilms is also briefly described in the third part. These novel bioactive and therapeutic polymeric materials and treatment methods have great potential to inhibit periodontitis and protect tooth structures.

Bone regeneration around immediate placed implant of molar teeth with autologous platelet-rich fibrin: Two case reports.

RATIONALE: There are some challenges concerning immediate implant placement in molar region. Platelet-rich fibrin (PRF), a second generation platelet concentrate, is an autologous fibrin matrix and contains platelets, growth factors, and leukocytes. It is used for tissue healing and regeneration in periodontal and oral-maxillofacial surgery. We report 2 cases of immediate placed implant of molar teeth with autologous PRF to improve and accelerate tissue healing. PATIENT CONCERNS: Case 1 was a 38-year-old female patient with masticatory discomfort. Case 2 was a 43-year-old male patient with a demand for his left mandibular posterior tooth restoration. DIAGNOSES: Through the clinical and radiographic examination, the patient in case 1 was diagnosed with vertical root crown fracture of the maxillary right first molar. The patient in case 2 was diagnosed with residual root of the left mandibular first molar via cone-beam computer tomography and clinical examination. INTERVENTIONS: The 2 patients underwent extraction of the molar teeth and immediate placed implant of molar teeth with autologous PRF was performed. In case 1, the gap between the implant surface and the socket walls of freshly extracted tooth was filled with PRF mixed with a commercial spongious bone substitute, followed by 2 PRF membranes coverage for protection. In case 2, PRF was used as a sole bone substitute material, placed between immediate implant and the socket wall of freshly extracted tooth. OUTCOMES: Follow-up of 2 cases revealed successful osseointegration and matured gingiva with optimal form and function. LESSONS: The results suggested that PRF could solely serve as a bone scaffold in 4-wall bony defects, or can be combined with xenograft in 3-wall bony defects during immediately placed implants in molar regions, exhibiting excellent biocompatibility and good soft and hard tissue healing.

Effects of quercetin on human oral keratinocytes during re-epithelialization: An in vitro study.

BACKGROUND: The width of keratinized mucosa plays an important role in esthetic and functional outcomes of dental implants. Lack of keratinized mucosa may lead to poor oral hygiene and greater soft-tissue recession. This study aimed at assessing the potential of quercetin in promoting human oral keratinocyte (HOK) proliferation and re-epithelialization in vitro. MATERIALS AND METHODS: HOK were detected in the absence or presence of test substances. The Cell Counting Kit-8 was used to assess cell viability and proliferation capacity. Re-epithelization was assessed using a keratinocyte monolayer scratch assay. Cell migration was monitored via Transwell chambers. Porphyromonas gingivalis lipopolysaccharide was used to stimulate keratinocytes for mimicking the inflammatory situation. mRNA expression of inflammatory cytokines (interleukin-1beta, IL-1ß and tumor necrosis factor alpha, TNF-α), cell adhesion molecules (Integrin-α6, Integrin-ß4), and growth factors (transforming growth factor beta 1,TGF-ß1 and transforming growth factor beta 3, TGF-ß3) were estimated using RT-qPCR. Protein contents of TGF-ß1 and TGF-ß3 were investigated by enzyme-linked immunosorbent assay. RESULTS: Multiplex analysis revealed that quercetin enhances HOK proliferation via an upregulation of adhesion molecules (Integrin-α6ß4). Additionally, re-epithelialization rate was significantly greater in the presence of quercetin than in the control (P < 0.01). Furthermore, 20 µM of quercetin increases both mRNA and protein levels of TGF-ß3 under basal and wound conditions without affecting TGF-ß1 production. Expressions of pro-inflammatory cytokines were downregulated by quercetin treatment. CONCLUSION: Quercetin promotes HOKs proliferation and oral re-epithelialization in vitro.