Molded porous poly (L-lactide) membranes for guided bone regeneration with enhanced effects by controlled growth factor release

The effect of 3-D printed polylactic acid scaffold with and without hyaluronic acid on bone regeneration

BACKGROUND

Three- dimensional (3D) technology has been suggested to overcome these limitations in guided bone regeneration (GBR) procedures because 3D-printed scaffolds can be easily molded to patient-specific bone defect site. This study aimed to investigate the effect of 3-D printed polylactic acid (PLA) scaffolds with or without hyaluronic acid (HA) in a rabbit calvaria model.

METHODS

A calvaria defect with a diameter of 15 mm was created in 30 New Zealand white rabbits. The rabbits were randomly allocated into 3 groups including no graft group (control, n = 10) , 3D printed PLA graft group (3D-PLA, n = 10) , and 3D printed PLA with hyaluronic acid graft group (3D-PLA/HA, n = 10) . Five animals in each group were sacrificed at 4 and 12 weeks after surgery. Microcomputed tomography and histologic and histomorphometric analyses were performed.

RESULTS

Over the whole examination period, no significant adverse reactions were observed. There were no statistically significant differences in bone volume (BV) /tissue volume (TV) among the three groups at 4 weeks. However, the highest BV/TV was observed in the 3D-PLA/HA group at 12 weeks. The new bone area for control, 3D-PLA, and 3D-PLA/HA showed no statistical differences at 4 weeks. However, the value was significantly higher in the 3D-PLA and 3D-PLA/HA groups compared to the control group at 12 weeks.

CONCLUSION

The 3D printed PLA scaffolds was biocompatible and integrated well with bone defect margin. They were also provided the proper space for new bone formation. Therefore, 3D printed PLA/HA might be a potential tool to enhance bone augmentation. This article is protected by copyright. All rights reserved.

Development of Zoledronic Acid Containing Biomaterials for Enhanced Guided Bone Regeneration

In recent years, biomaterial-based treatments, also called guided bone regeneration (GBR), which aim to establish a bone regeneration site and prevent the migration of gingival connective tissue and / or peripheral epithelium through the defective area during periodontal surgical procedures have come to the fore. In this report, we have developed a nanoparticle bearing thermosensitive in situ gel formulation of Pluronic F127 and poly(D,L-lactic acid) based membrane to reveal their utilization at GBR by in-vivo applications. In addition, the encouragement of the bone formation in defect area via inhibition of osteoclastic activity is intended by fabrication these biodegradable biomaterials at a lowered Zoledronic Acid (ZA) dose. Both of the developed materials remained stable under specified stability conditions (25 °C, 6 months) and provided the extended release profile of ZA. The in-vivo efficacy of nanoparticle bearing in situ gel formulation, membrane formulation and simultaneous application for guided bone regeneration was investigated in New Zealand female rabbits with a critical size defect of 0.5 × 0.5 cm in the tibia bone for eight weeks. Based on the histopathological findings, lamellar bone and primarily woven bone formations were observed after 8 weeks of post-implantation of both formulations, while fibrosis was detected only in the untreated group. Lamellar bone growth was remarkably achieved just four weeks after the simultaneous application of formulations. Consequently, the simultaneous application of ZA-membrane and ZA-nanoparticles loaded in-situ gel formulations offers enhanced and faster GBR therapy alternatives.

Adsorption and release kinetics of growth factors on barrier membranes for guided tissue/bone regeneration: A systematic review

OBJECTIVES

Guided bone / tissue regeneration (GBR/GTR) procedures are necessary to improve conditions for implant placement. These techniques in turn can be enhanced by using growth factors (GFs) such as bone morphogenetic protein (BMP-2) and platelet-derived growth factor (PDGF) to accelerate regeneration. The aim of the present systematic review was to evaluate the GF loading and release kinetics of barrier membranes.

STUDY DESIGN

A total of 138 articles were screened in PubMed databases, and 31 meeting the inclusion criteria were included in the present systematic review.

RESULTS

All the articles evaluated bio-resorbable membranes, especially collagen or polymer-based membranes. In most studies, the retention and release kinetics of osteogenic GFs such as BMP-2 and PDGF were widely investigated. Growth factors were incorporated to the membranes by soaking and incubating the membranes in GF solution, followed by lyophilization, or mixing in the polymers before evaporation. Adsorption onto the membranes depended upon the membrane materials and additional reagents such as heparin, cross-linkers and GF concentration. Interestingly, most studies showed two phases of GF release from the membranes: a first phase comprising a burst release (about 1 day), followed by a second phase characterized by slower release. Furthermore, all the studies demonstrated the controlled release of sufficient concentrations of GFs from the membranes for bioactivities.

CONCLUSIONS

The adsorption and release kinetics varied among the different materials, forms and GFs. The combination of membrane materials, GFs and manufacturing methods should be considered for optimizing GBR/GTR procedures.

Preclinical induced membrane model to evaluate synthetic implants for healing critical bone defects without autograft

Critical bone defects pose a formidable orthopaedic problem in patients with bone loss. We developed a preclinical model based on the induced membrane technique using a synthetic graft to replace autograft for healing critical bone defects. Additionally, we used a novel osteoconductive scaffold coupled with a synthetic membrane to evaluate the potential for single-stage bone regeneration. Three experimental conditions were investigated in critical femoral defects in rats. Group A underwent a two-stage procedure with insertion of a polymethylmethacrylate (PMMA) spacer followed by replacement with a 3D printed polycaprolactone(PCL)/β-tricalcium phosphate (β-TCP) osteoconductive scaffold after 4 weeks. Group B received a single-stage PCL/β-TCP scaffold wrapped in a PCL-based microporous polymer film creating a synthetic membrane. Group C received a single-stage bare PCL/β-TCP scaffold. All groups were examined by serial radiographs for callus formation. After 12 weeks, the femurs were explanted and analyzed with micro-CT and histology. Mean callus scores tended to be higher in Group A. Group A showed statistically significant greater bone formation on micro-CT compared with other groups, although bone volume fraction was similar between groups. Histology results suggested extensive bone ingrowth and new bone formation within the macroporous scaffolds in all groups and cell infiltration into the microporous synthetic membrane. This study supports the use of a critical size femoral defect in rats as a suitable model for investigating modifications to the induced membrane technique without autograft harvest. Future investigations should focus on bioactive synthetic membranes coupled with growth factors for single-stage bone healing. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Physical Stimulations for Bone and Cartilage Regeneration

A wide range of techniques and methods are actively invented by clinicians and scientists who are dedicated to the field of musculoskeletal tissue regeneration. Biological, chemical, and physiological factors, which play key roles in musculoskeletal tissue development, have been extensively explored. However, physical stimulation is increasingly showing extreme importance in the processes of osteogenic and chondrogenic differentiation, proliferation and maturation through defined dose parameters including mode, frequency, magnitude, and duration of stimuli. Studies have shown manipulation of physical microenvironment is an indispensable strategy for the repair and regeneration of bone and cartilage, and biophysical cues could profoundly promote their regeneration. In this article, we review recent literature on utilization of physical stimulation, such as mechanical forces (cyclic strain, fluid shear stress, etc.), electrical and magnetic fields, ultrasound, shock waves, substrate stimuli, etc., to promote the repair and regeneration of bone and cartilage tissue. Emphasis is placed on the mechanism of cellular response and the potential clinical usage of these stimulations for bone and cartilage regeneration.

Suppressing inflammation and enhancing osteogenesis using novel CS-EC@Ca microcapsules

The aim of this study was to investigate the suppression of inflammation and enhancement of osteogenesis using chitosan-coated calcium hydroxide-loaded microcapsules (CS-EC@Ca microcapsules) in vivo. Circular defects were created in the mandibular bones of rabbits and filled with Ca(OH)₂ , Bio-oss, or CS-EC@Ca microcapsules, and rabbits without drug implantation served as the controls. Lipopolysaccharides were injected in situ daily in all groups for 7 days. Mandibular bones were investigated at 4 and 12 weeks after surgery using micro-CT, histological observations, and real-time PCR analysis. At the postoperation, there was more substantial nascent bone in the microcapsule and Bio-oss groups than in the control group. The recovery of the rabbits in the Ca(OH)₂ group was slower than the control group, as determined using micro-CT and histological staining. Osteocalcin and collagen type I production was not significantly different between the microcapsule and Bio-oss groups (p > 0.05), but the expression levels of the two molecules were significantly increased compared to the control and Ca(OH)₂ groups at postoperation (p < 0.05). The mRNA transcript levels of inflammatory factors in the microcapsule group had the most reduced expression of IL-6 and TNF-α (p < 0.05). The microcapsules significantly reduced inflammation and promoted osteogenesis in this rabbit model of inflammatory bone destruction. Our findings indicate that CS-EC@Ca microcapsules hold potential for use in apical periodontitis treatment. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3222-3230, 2018.

BMP-2-Immobilized Porous Matrix with Leaf-Stacked Structure as a Bioactive GBR Membrane

We developed an asymmetrically porous membrane with a leaf-stacked structure (LSS membrane; top with nanosized pores and bulk/bottom with leaf-stacked structure) via immersion-precipitation using polycarprolactone (PCL)/Pluronic F127 mixture solution (in tetraglycol). The bone morphogenetic protein-2 (BMP-2) is immobilized on the pore surfaces of the LSS membrane by immersing the membrane in the BMP-2 solution. The BMP-2 loaded in the LSS membrane is continuously released for 38 days (without additional modifications of the matrix) to improve osteogenic differentiation of cells and new bone formation (carvarial defect rat model). The leaf-stacked structure is recognized to be a physical stimulus for bone regeneration, and the stimulation effect is comparable to that of continuously released BMP-2. Moreover, we observe the combined effect of BMP-2 and the leaf-stacked structure for bone healing. Thus, we suggest that the BMP-2-immobilized LSS membrane may be a candidate as a bioactive guided bone regeneration (GBR) membrane for clinical applications, due to the use of clinically acceptable biomaterials and fabrication procedures as well as effective osteogenic differentiation and bone regeneration.

Guided bone regeneration with polypropylene barrier in rabbit's calvaria: A preliminary experimental study

Objectives

This study aimed to evaluate the bone formation process in experimental defects created on rabbit calvarial, in which one of the bone defects was covered by the impermeable membrane before suturing the skin flap, while the other was closed only by the cutaneous flap. The experimental holes were filled only by the blood clot.

Material and methods

Sixteen New Zealand female rabbits weighing between 3.5 and 4 kg were used. Two experimental bone defects were made in the rabbit calvarial. The holes were filled only with the blood clot and one of them was covered with an impermeable polypropylene membrane. A histological analysis was made at 21 and 42 days following the surgery. Histological evaluation consisted of the following: 1. inflammatory process; 2. Bone repair; 3. Bone remodeling; 4. Presence of osteoid matrix and mineralization, and 5. Formation of hematopoietic tissue. Each characteristic was analyzed semi quantitatively.

Results

There was a statistical difference between the test and the control group at 21 days of healing in the following items: presence of cementation line (p = 0.012), presence of osteoid tissue (p = 0.012), and trabecular bone tissue development and mineralization (p = 0.012). A greater amount of lamellar bone tissue (mature) was also observed in the test group compared to the control group.

Conclusion

The semiquantitative analysis showed that at 21 days there was a superiority of the repair process in the test group; at 42 days there was no significant difference in bone formation between the two groups; and that the polypropylene membrane is feasible to be used in GBR.

Clinical significance

The impermeable polypropylene barrier is feasible for use in the guided bone regeneration technique. It can be used only on the blood clot, without the need for grafting, and can be easily removed a few days after surgery. These results are unprecedented.

Influence of Chromium-Cobalt-Molybdenum Alloy (ASTM F75) on Bone Ingrowth in an Experimental Animal Model

Cr-Co-Mo (ASTM F75) alloy has been used in the medical environment, but its use as a rigid barrier membrane for supporting bone augmentation therapies has not been extensively investigated. In the present study, Cr-Co-Mo membranes of different heights were placed in New Zealand white, male rabbit tibiae to assess the quality and volume of new bone formation, without the use of additional factors. Animals were euthanized at 20, 30, 40, and 60 days. Bone formation was observed in all of the cases, although the tibiae implanted with the standard membranes reached an augmentation of bone volume that agreed with the density values over the timecourse. In all cases, plasmatic exudate was found under the membrane and in contact with the new bone. Histological analysis indicated the presence of a large number of chondroblasts adjacent to the inner membrane surface in the first stages, and osteoblasts and osteocytes were observed under them. The bone formation was appositional. The Cr-Co-Mo alloy provides a scaffold with an adequate microenvironment for vertical bone volume augmentation, and the physical dimensions and disposition of the membrane itself influence the new bone formation.

* Engineering Membranes for Bone Regeneration

This review is focused on the use of membranes for the specific application of bone regeneration. The first section focuses on the relevance of membranes in this context and what are the specifications that they should possess to improve the regeneration of bone. Afterward, several techniques to engineer bone membranes by using "bulk"-like methods are discussed, where different parameters to induce bone formation are disclosed in a way to have desirable structural and functional properties. Subsequently, the production of nanostructured membranes using a bottom-up approach is discussed by highlighting the main advances in the field of bone regeneration. Primordial importance is given to the promotion of osteoconductive and osteoinductive capability during the membrane design. Whenever possible, the films prepared using different techniques are compared in terms of handability, bone guiding ability, osteoinductivity, adequate mechanical properties, or biodegradability. A last chapter contemplates membranes only composed by cells, disclosing their potential to regenerate bone.

Use of platelet concentrates in oral and maxillofacial surgery: an overview

OBJECTIVE

To describe and provide a comprehensive overview on the development, use and efficacy of autologous platelet concentrates in different in vitro and in vivo studies focusing on oral and maxillofacial pathologies.

MATERIALS AND METHODS

Present work employs an extensive critical overview of the literature on the development and application of platelet concentrates.

RESULTS

Platelet concentrates are innovative endogenous therapeutic agents which gained a lot of interest in different medical and dental disciplines due to their potential ability to stimulate and increase regeneration of soft and hard tissues. The effect of platelet-derived products is considered to be a result of the high number of platelets which contain a wide range of growth factors. They are not just therapeutic products but autologous blood concentrates containing active molecules. The quality of platelet concentrates may vary according to the individual physical state of donors making it difficult to to compare the outcomes of their application. Although, there are many studies analyzing the properties of these biomaterials both in vivo and in vitro, a consensus regarding their efficacy still has to be reached.

CONCLUSION

Evidences described in the literature on the efficacy of platelet concentrates in procedures in oral and maxillofacial region are controversial and limited. In order to clarify the real advantages and priorities for the patients, when the blood-derived products are applied, further in vitro and in vivo research about the activity of PRP and PRF on the dental cells biology should be conducted.

Bi-layered constructs of poly(glycerol-sebacate)-β-tricalcium phosphate for bone-soft tissue interface applications

This study aims to establish a facile protocol for the preparation of a bi-layered poly(glycerol-sebacate) (PGS)/β-tricalcium phosphate (β-TCP) construct and to investigate its potential for bone-soft tissue engineering applications. The layered structure was prepared by distributing the ceramic particles within a prepolymer synthesized in a microwave reactor followed by a cross-linking of the final construct in vacuum (<10mbar). The vacuum stage led to the separation of cross-linked elastomer (top) and ceramic (bottom) phases. Results showed that addition of β-TCP particles to the elastomer matrix after the polymerization led to an increase in compression strength (up to 14±2.3MPa). Tensile strength (σ), Young's modulus (E), and elongation at break (%) values were calculated as 0.29±0.03MPa and 0.21±0.03; 0.38±0.02 and 1.95±0.4; and 240±50% and 24±2% for PGS and PGS/β-TCP bi-layered constructs, respectively. Morphology was characterized by using Scanning Electron Microscopy (SEM) and micro-computed tomography (μ-CT). Tomography data revealed an open porosity of 35% for the construct, mostly contributed from the ceramic phase since the elastomer side has no pore. Homogeneous β-TCP distribution within the elastomeric structure was observed. Cell culture studies confirmed biocompatibility with poor elastomer-side and good bone-side cell attachment. In a further study to investigate the osteogenic properties, the construct were loaded with BMP-2 and/or TGF-β1. The PGS/β-TCP bi-layered constructs with improved mechanical and biological properties have the potential to be used in bone-soft tissue interface applications where soft tissue penetration is a problem.

Stem cells, growth factors and scaffolds in craniofacial regenerative medicine

Current reconstructive approaches to large craniofacial skeletal defects are often complicated and challenging. Critical-sized defects are unable to heal via natural regenerative processes and require surgical intervention, traditionally involving autologous bone (mainly in the form of nonvascularized grafts) or alloplasts. Autologous bone grafts remain the gold standard of care in spite of the associated risk of donor site morbidity. Tissue engineering approaches represent a promising alternative that would serve to facilitate bone regeneration even in large craniofacial skeletal defects. This strategy has been tested in a myriad of iterations by utilizing a variety of osteoconductive scaffold materials, osteoblastic stem cells, as well as osteoinductive growth factors and small molecules. One of the major challenges facing tissue engineers is creating a scaffold fulfilling the properties necessary for controlled bone regeneration. These properties include osteoconduction, osetoinduction, biocompatibility, biodegradability, vascularization, and progenitor cell retention. This review will provide an overview of how optimization of the aforementioned scaffold parameters facilitates bone regenerative capabilities as well as a discussion of common osteoconductive scaffold materials.

Effect of a chitosan sponge impregnated with platelet-derived growth factor on bone augmentation beyond the skeletal envelope in rat calvaria

We evaluated the ability of platelet-derived growth factor (PDGF) to promote bone augmentation beyond the skeletal envelope in rat calvaria. The calvariae of 14 rats were exposed, and two plastic caps-one with 0.03% PDGF and a chitosan sponge and one with a chitosan sponge alone-were placed. Microcomputed tomography and histologic sections were used to determine the amount of bone augmentation within the plastic caps. Bone volume was calculated using measurement software. Bone volume and amount of bone augmentation were significantly greater in the PDGF group than in the control group. In conclusion, a chitosan sponge containing 0.03% PDGF enhanced bone formation beyond the skeletal envelope in rat calvaria.

Recombinant Human Bone Morphogenetic Protein 9 (rhBMP9) Induced Osteoblastic Behavior on a Collagen Membrane Compared With rhBMP2

BACKGROUND

Bone morphogenetic protein 9 (BMP9) has previously been characterized as one of the most osteogenic growth factors of the BMP family. To the best of the authors' knowledge, previous experiments have only used adenovirus transfection (gene therapy). With the recent development of recombinant human BMP9 (rhBMP9), the present study investigates the osteopromotive potential of BMP9 versus rhBMP2 when loaded onto collagen membranes.

METHODS

ST2 stromal bone marrow cells were seeded onto: 1) control; 2) low-dose rhBMP2 (10 ng/mL); 3) high-dose rhBMP2 (100 ng/mL); 4) low-dose rhBMP9 (10 ng/mL); and 5) high-dose rhBMP9 (100 ng/mL) porcine collagen membranes. The following parameters were compared among groups: 1) cell adhesion (at 8 hours); 2) cell proliferation (at 1, 3, and 5 days); 3) real-time polymerase chain reaction for genes encoding runt-related transcription factor 2; 4) alkaline phosphatase (ALP); 5) bone sialoprotein ([BSP] at 3 and 14 days); and 6) alizarin red staining (at 14 days).

RESULTS

rhBMP2 and rhBMP9 demonstrated little effect on cell attachment and proliferation; however, pronounced increases were observed in osteoblast differentiation. All groups significantly induced ALP messenger RNA (mRNA) levels at 3 days and BSP levels at 14 days; however, high-dose rhBMP9 showed significantly higher values compared with all other groups for ALP levels (five-fold increase at 3 days and two-fold increase at 14 days). Alizarin red staining further revealed both concentrations of rhBMP9 induced up to three-fold more staining compared with rhBMP2.

CONCLUSIONS

Results indicate that the combination of collagen membranes with rhBMP9 induced significantly higher ALP mRNA expression and alizarin red staining compared with rhBMP2. These findings suggest that rhBMP9 may be a suitable growth factor for future regenerative procedures in bone biology.

Bioresorbable zinc hydroxyapatite guided bone regeneration membrane for bone regeneration

OBJECTIVES

The aim of this study was to investigate the bone regenerative properties of a heat treated cross-linked GBR membrane with zinc hydroxyapatite powders in the rat calvarial defect model over a 6-week period.

MATERIAL AND METHODS

In vitro physio-chemical characterization involved X-ray diffraction analysis, surface topology by scanning electron microscopy, and zinc release studies in physiological buffers. Bilateral rat calvarial defects were used to compare the Zn-HAp membranes against the commercially available collagen membranes and the unfilled defect group through radiological and histological evaluation.

RESULTS

The synthesized Zn-MEM (100 μm thick) showed no zinc ions released in the phosphate buffer solution (PBS) buffer, but zinc was observed under acidic conditions. At 6 weeks, both the micro-CT and histological analyses revealed that the Zn-MEM group yielded significantly greater bone formation with 80 ± 2% of bone filled, as compared with 60 ± 5% in the collagen membrane and 40 ± 2% in the unfilled control group.

CONCLUSION

This study demonstrated the use of heat treatment as an alternative method to cross-linking the Zn-MEM to be applied as a GBR membrane. Its synthesis and production are relatively simple to fabricate, and the membrane had rough surface features on one side, which might be beneficial for cellular activities. In a rat calvarial defect model, it was shown that new bone formation was accelerated in comparison with the collagen membrane and the unfilled defect groups. These results would suggest that Zn-MEM has the potential for further development in dental applications.

Platelet‑derived growth factor promotes osteoblast proliferation by activating G‑protein‑coupled receptor kinase interactor‑1

Platelet‑derived growth factor (PDGF) has been reported to stimulate bone fracture‑healing. Multiple studies have demonstrated that PDGF has a critical role in osteoblast or osteoprogenitor cell activation, although the underlying mechanism remains unclear. Studies have found that G‑protein‑coupled receptor kinase interactor‑1 (GIT1) is activated by PDGF and described as an important factor in bone metabolism. In the present study, the effects of PDGF and GIT1 on the proliferation and apoptosis of osteoblasts were investigated in cultured osteoblasts isolated from rat calvaria with PDGF stimulation and GIT1 small interfering RNA transfection. The results demonstrated that PDGF rapidly stimulated GTI1 expression in osteoblasts, increased osteoblast proliferation and inhibited cell apoptosis. Furthermore, cyclin D1 expression was significantly upregulated, the number of cells in the G0/G1 phase was decreased, while the number in the S phase was increased. In cells with knockdown of GIT1, the change stimulated by PDGF was not evident. The results indicate that, PDGF stimulated GIT1 activation of cyclin D1 expression, thereby promoting osteoblasts to enter the S phase from the stationary G0/G1 phase, leading to the proliferation of osteoblasts.

The role of barrier membranes for guided bone regeneration and restoration of large bone defects: current experimental and clinical evidence

Treatment of large bone defects represents a great challenge in orthopedic and craniomaxillofacial surgery. Although there are several methods for bone reconstruction, they all have specific indications and limitations. The concept of using barrier membranes for restoration of bone defects has been developed in an effort to simplify their treatment by offering a single-staged procedure. Research on this field of bone regeneration is ongoing, with evidence being mainly attained from preclinical studies. The purpose of this review is to summarize the current experimental and clinical evidence on the use of barrier membranes for restoration of bone defects in maxillofacial and orthopedic surgery. Although there are a few promising preliminary human studies, before clinical applications can be recommended, future research should aim to establish the 'ideal' barrier membrane and delineate the need for additional bone grafting materials aiming to 'mimic' or even accelerate the normal process of bone formation. Reproducible results and long-term observations with barrier membranes in animal studies, and particularly in large animal models, are required as well as well-designed clinical studies to evaluate their safety, efficacy and cost-effectiveness.

Poly D,L-lactide-co-glycolic acid (PLGA)-encapsulated vaccine on immune system in Epinephelus bruneus against Uronema marinum

We investigate the efficacy of poly D,L-lactide-co-glycolic acid (PLGA)-encapsulated vaccine on innate and adaptive immune response in kelp grouper (Epinephelus bruneus) against Uronema marinum at weeks 1, 2, and 4. The respiratory burst (RB) activity, complement activity, and α2-macroglobulin were significantly enhanced in fish immunization with vaccine on week 4 whereas vaccine and PLGA-encapsulated vaccine from weeks 1 to 4. The serum lysozyme activity, antiprotease activity, and antibody level were significantly enhanced in fish immunized with vaccine and PLGA-encapsulated vaccine on weeks 2 and 4. The cumulative mortality was low in PLGA-encapsulated vaccine with 20% whereas high in PLGA and vaccine with 40% and 30%. The results from the present study suggest that PLGA-encapsulated vaccine is useful for further design of immunoprophylatic nano formulation against scuticociliatosis.

Fibrous membrane of nano-hybrid poly-L-lactic acid/silica xerogel for guided bone regeneration

Nanofibrous membranes, consisting of a poly(L-lactic acid) (PLLA)-silica xerogel hybrid material, were successfully fabricated from a hybrid sol using the electrospinning technique for guided bone regeneration (GBR) application. These hybrid nanofibers exhibited a homogeneous and continuous morphology, with a nano-sized dispersed silica xerogel phase in the PLLA fiber matrix. The mechanical properties, such as the tensile strength and the elastic modulus, were improved as the silica xerogel content increased up to 40%. All of the hybrid membranes exhibited highly hydrophilic surfaces and good proliferation levels. After culturing for 13 days, the cells that were cultured on the hybrid membranes exhibited a significantly higher ALP activity compared to the pure PLLA membrane. Moreover, the in vivo animal experiments that used the rat calvarial defect model revealed a remarkably improved bone regeneration ability for the hybrid membrane compared to pure PLLA. These results demonstrated the feasibility of these hybrid membranes for efficient GBR.

From natural bone grafts to tissue engineering therapeutics: Brainstorming on pharmaceutical formulative requirements and challenges

Tissue engineering is an emerging multidisciplinary field of investigation focused on the regeneration of diseased or injured tissues through the delivery of appropriate molecular and mechanical signals. Therefore, bone tissue engineering covers all the attempts to reestablish a normal physiology or to speed up healing of bone in all musculoskeletal disorders and injuries that are lashing modern societies. This article attempts to give a pharmaceutical perspective on the production of engineered man-made bone grafts that are described as implantable tissue engineering therapeutics, and to highlight the importance of understanding bone composition and structure, as well as osteogenesis and bone healing processes, to improve the design and development of such implants. In addition, special emphasis is given to pharmaceutical aspects that are frequently minimized, but that, instead, may be useful for formulation developments and in vitro/in vivo correlations.

Assessment of the potential of growth factors for localized alveolar ridge augmentation: a systematic review

OBJECTIVE

To systematically assess the literature regarding the clinical, histological, and radiographic outcome of bone morphogenetic proteins (BMP-2, BMP-7), growth/differentiation factor-5 (GDF-5), platelet-derived growth factor (PDGF), and parathyroid hormone (PTH) for localized alveolar ridge augmentation.

MATERIAL AND METHODS

Five separate Medline searches were performed in duplicate for human and animal studies, respectively. The primary outcome of the included studies was bone regeneration of localized alveolar ridge defects or craniofacial defects.

RESULTS

In six human studies, BMP-2 affected local bone augmentation with increasing volume for higher doses. A majority (43 of 45) of animal studies using BMP-2 showed a positive effect in favour of the growth factor (GF). In six of eight studies, a positive effect was associated with the use of BMP-7. Only one animal study was included for GDF-5 revealing statistically significantly higher bone volume. Regarding PDGF, statistically significantly higher bone volume was observed in five of 10 included studies. Four animal studies using PTH revealed statistically significantly more bone regeneration compared with controls.

CONCLUSIONS

Differing levels and quantity of evidence were noted to be available for the GFs evaluated, revealing that BMP-2, BMP-7, GDF-5, PDGF, and PTH may stimulate local bone augmentation to various degrees. Human data for the potential of rhBMP-2 are supportive.

Preparation and in vitro characterization of scaffolds of poly(L-lactic acid) containing bioactive glass ceramic nanoparticles

Porous nanocomposite scaffolds of poly(l-lactic acid) (PLLA) containing different quantities of bioactive glass ceramic (BGC) nanoparticles (SiO(2):CaO:P(2)O(5) approximately 55:40:5 (mol)) were prepared by a thermally induced phase-separation method. Dioxane was used as the solvent for PLLA. Introduction of less than 20wt.% of BGC nanoparticles did not remarkably affect the porosity of PLLA foam. However, as the BGC content increased to 30wt.%, the porosity of the composite was observed to decrease rapidly. The compressive modulus of the scaffolds increased from 5.5 to 8.0MPa, while the compressive strength increased from 0.28 to 0.35MPa as the BGC content increased from 0 to 30wt.%. The in vitro bioactivity and biodegradability of nanocomposites were investigated by incubation in simulated body fluid (SBF) and phosphate-buffered saline, respectively. Scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction were employed to monitor the surface variation of neat PLLA and PLLA/BGC porous scaffolds during incubation. PLLA/(20wt.%)BGC composite exhibited the best mineralization property in SBF, while the PLLA/(10wt.%)BGC composite showed the highest water absorption ability.

Control of silicon species released from poly(lactic acid)-polysiloxane hybrid membranes

Novel hybrid membranes consisting of poly(L-lactic acid) (PLLA), aminopropyltriethoxysilane (APTES), and calcium carbonates were prepared for bioresorbable guided bone regeneration. A molecular chain of PLLA was bonded at the end of an organic chain in APTES through the amide bond formed between carboxy-groups in PLLA and amino-groups in ATPES. As a result, the hybrid membrane was formed. The PLLA in the membrane was an amorphous phase. By heating the membrane at 100 degrees C for 1 h, the PLLA in the membrane crystallized and some organic chains in APTES and amide bonds decomposed. Moreover, numerous pores of 0.5-1 microm in diameter were newly formed at the surface. When the membranes before and after heat treatment were soaked in simulated body fluid, the amount of silicon species in SBF released from the membrane after heat treatment was higher than that before heat treatment. A test of osteoblast-like cellular proliferation on the membrane showed that the membrane after heat treatment has much higher cell-proliferation ability than that before heat treatment.

Heterotopic Bone Formation Around Sintered Porous-Surfaced Ti-6Al-4V Implants Coated with Native Bone Morphogenetic Proteins

PURPOSE

Coating endosseous dental implants with growth factors such as bone morphogenetic proteins (BMPs) may be one way to accelerate and/or enhance the quality of osseointegration. The purpose of this study was to investigate in the murine muscle pouch model whether sintered porous-surfaced titanium alloy implants coated with BMPs would lead to heterotopic bone formation around and within the implant surface geometry.

MATERIALS

Porous-surfaced dental implants were coated with partially purified native human BMPs, with or without a carrier of Poloxamer 407 (BASF Corp., Parsippany, NJ), placed in gelatin capsules and implanted into the hindquarter muscles of mice. Mice were euthanized after 28 days. Sections of retrieved specimens were subsequently prepared for morphometric analysis of bone formation using backscatter electron microscopic images.

RESULTS

Human BMPs, either with or without the carrier of Poloxamer 407, led to bone formation within and outside of the sintered porous implant surface. When the sintered implant surface region was subdivided into inner and outer halves, similar levels of bone ingrowth and contact were seen in the 2 halves. Evidence of bone formation to the depth of the solid implant core (i.e., the deepest level possible) also was seen.

DISCUSSION AND CONCLUSIONS

Sintered porous-surfaced dental implants can be used as substrate for partially purified BMPs in the murine muscle pouch model. With the addition of these osteoinductive factors, the porous implant surface supported bone formation within the surface porosity provided, in some instances, all the way to the solid implant core. The addition of growth factors to a sintered porous surface may be an efficient method for altering locally the healing sequence and quality of bone associated with osseointegration of bone-interfacing implants.

Effect of FGF and Polylactide Scaffolds on Calvarial Bone Healing With Growth Factor on Biodegradable Polymer Scaffolds

Repair of bone defects remains a major concern in reconstructive surgery. Synthetic biodegradable polymers have been used as scaffolds for guided bone regeneration. Fibroblast growth factors (FGFs) promote cell growth, differentiation, and tissue maintenance factors. They can stimulate the proliferation of osteogenic cells and chondrocytes, and also promote angiogenesis. Acidic and basic fibroblast growth factors (FGF-1 and FGF-2, respectively) are the best known members of this protein family. To evaluate the healing of experimental bone defects using poly-L/D-lactide (PLDLA) 96/4 scaffolds and FGF-1, 18 adult rats were operated on. A 6-mm diameter critical size defect (CSD) was made in the calvarial bone of each rat. The animals were divided into three treatment groups: 1) Neither scaffold nor FGF was used (control group); 2) scaffold only; and 3) scaffold with FGF-1. Follow-up time was eight weeks. Samples were embedded in methylmethacrylate and 5-microm thick sections from the middle of each specimen were stained with modified Masson-Goldner method. The shape and size of defects were evaluated radiologically. New bone formation was measured histologically and histomorphometrically. Radiologically, in the control group the shape of the defects changed from round to oval and edges were blunt. In the other groups the defects were round with sharp edges. Histomorphometrically, mean surface area of bone trabeculae was 1.05 mm (SD +/- 0.25) in group 1 (no implant), 1.35 mm (SD +/- 0.52) in group 2 (implant) and 0.79 mm (SD +/- 0.34) in group 3 (implant and FGF-1). Histological examinations revealed no or little osteoid in the groups 1 and 2, whereas in the group 3 samples had little or moderate new bone formation. Accordingly, no clear benefit of using knitted PLDLA scaffolds combined with FGF-1 on the healing of calvarial critical size defects in rats could be demonstrated.

A citric acid-based hydroxyapatite composite for orthopedic implants

We describe a novel approach to process bioceramic microparticles and poly(diol citrates) into bioceramic-elastomer composites for potential use in orthopedic surgery. The composite consists of the biodegradable elastomer poly(1,8-octanediol-citrate) (POC) and the bioceramic hydroxyapatite (HA). The objective of this work was to characterize POC-HA composites and assess the feasibility of fabricating tissue fixation devices using machining and molding techniques. The mechanical properties of POC-HA composites with HA (40, 50, 60, 65wt.%) were within the range of values reported for tissue fixation devices (for POC-HA 65wt.%, S(b)=41.4+/-3.1, E(b)=501.7+/-40.3, S(c)=74.6+/-9.0, E(c)=448.8+/-27.0, S(t)=9.7+/-2.3, E(t)=334.8+/-73.5, S(s)=27.7+/-2.4, T(s)=27.3+/-4.9, all values in MPa). At 20 weeks, the weight loss of POC-HA composites ranged between 8 and 12wt.%, with 65wt.% HA composites degrading the slowest. Exposure of POC-HA to simulated body fluid resulted in extensive mineralization in the form of calcium phosphate with Ca/P of 1.5-1.7 similar to bone. POC-HA supported osteoblast adhesion in vitro and histology results from POC-HA samples that were implanted in rabbit knees for 6 weeks suggest that the composite is biocompatible. Synthesis of POC-HA is easy and inexpensive, does not involve harsh solvents or initiators, and the mechanical properties of POC-HA with 65wt.% HA are suitable for the fabrication of potentially osteoconductive bone screws.

New administration model of trans-chalcone biodegradable polymers for the treatment of experimental leishmaniasis

The present study was designed to investigate a new administration model and the antileishmanial activity of a semi-synthetic chalcone, benzylideneacetophenone (trans-chalcone). The antileishmanial activity of this product was first tested in vitro against promastigotes of L. braziliensis, L. tropica, L. infantum and L. amazonensis. An in vivo experiment was carried out using subcutaneous administration of trans-chalcone and implants of synthetic biodegradable polymers, polylactic acid (PLA) and polylactic/glycolic acid (PLGA). This compound showed potent inhibitory effects on the growth of all Leishmania strains examinated. Subcutaneous administration of trans-chalcone at a single dose of 4 mg/kg of body weight reduced lesion development in mice infected with L. amazonensis. A similar inhibition of the lesion growth in mice treated with trans-chalcone and pentamidine was observed. PLA and PGLA implants of trans-chalcone at 4 mg/kg were administered to mice infected with L. amazonensis. PLGA implants induced a highest reduction in the lesion size (31.25%) than PLA implants (10.75%). Treatment in vitro with trans-chalcone at IC50, completely inhibited the pathogenicity of this parasite in vivo. The development of this model provides a new practical technique for delivering drugs and can be useful for experimental leishmaniasis treatment.

The effect of platelet-rich plasma on the cellular response of rat bone marrow cells in vitro

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on the proliferation and the differentiation of rat bone marrow cells (RBMCs). PRP, platelet-poor plasma (PPP), and bone marrow cells were derived from the rats (hearts and tibia) and the cells were cultured with or without PRP or PPP (0 [control]), 0.2 approximately 10 microL/mL). The proliferation of RBMCs was measured on days 2 and 4, and alkaline phosphatase (ALP) staining and activity measurement were evaluated to determine the effect of PRP on the differentiation on days 4 and 8. PRP enhanced the proliferation significantly compared to the control group (P < .05). These enhancements were greater than ones induced by the addition of PPP. ALP staining appeared to show that PRP decreased the number of ALP positive cells and ALP activity significantly (P < .05). Our results demonstrate that PRP stimulates the proliferation but suppresses the differentiation of RBMCs.

The contribution of platelet-derived growth factor, transforming growth factor-beta1, and insulin-like growth factor-I in platelet-rich plasma to the proliferation of osteoblast-like cells

The aim of this study was to investigate the effect of platelet-rich plasma (PRP) on the proliferation of osteoblast-like cells in vitro. PRP was prepared using a centrifuge; the number of platelets (n = 32) and the levels of platelet-derived growth factor-AB (PDGF-AB), transforming growth factor-beta1 (TGF-beta1), and insulin-like growth factor-I (IGF-I) were measured (n = 16). For the proliferation assay, SaOS-2 was cultured in the presence of platelet-poor plasma (PPP), whole blood, or PRP. The cell number was counted after 36 and 72 hours. To investigate the effect of each growth factor, the cells were cultured with PRP in the absence or presence of neutralizing antibodies, and counted as described. The mean platelet count of PRP was 1546.36 +/- 382.25 x 10(3)/microL, and the mean levels of PDGF-AB, TGF-beta1 and IGF-I were 0.271 +/- 0.043, 0.190 +/- 0.039, and 0.110 +/- 0.039 ng/1500 x 10(3) platelets, respectively. Cell proliferation was enhanced in all PRP groups in a dose-dependent manner, and all neutralizing antibodies significantly suppressed proliferation compared with the PRP group, lacking antibody, at 36 hours. However, at 72 hours, the neutralizing antibodies of PDGF and TGF-beta1, but not IGF-I, significantly suppressed proliferation. These results show the beneficial abilities of PRP in the proliferation of osteoblast-like cells from the standpoint of growth factors, including the contribution of each factor.

Cyclooxygenase-2 inhibition selectively attenuates bone morphogenetic protein-6 synthesis and bone formation during guided tissue regeneration in a rat model

OBJECTIVES

Bone formation during guided tissue regeneration is a tightly regulated process involving cells, extracellular matrix and growth factors. The aims of this study were (i) to examine the expression of cyclooxygenase-2 (COX-2) during bone regeneration and (ii) the effects of selective COX-2 inhibition on osseous regeneration and growth factor expression in the rodent femur model.

MATERIAL AND METHODS

A standardized transcortical defect of 5 x 1.5 mm was prepared in the femur of 12 male rats and a closed half-cylindrical titanium chamber was placed over the defect. The expression of COX-2 and of platelet-derived growth factor-B (PDGF-B), bone morphogenetic protein-6 (BMP-6) and insulin-like growth factor-I/II (IGF-I/II) was analyzed at Days 3, 7, 21 and 28 semiquantitatively by reverse transcriptase-polymerase chain reaction and immunohistochemistry. The effects of COX-2 inhibition by intraperitoneal injection of NS-398 (3 mg/kg/day) were analyzed in five additional animals sacrificed at Day 14.

RESULTS

Histomorphometry revealed that new bone formation occurred in the cortical defect area as well as in the supracortical region, i.e. region within the chamber by Day 7 and increased through Day 28. Immunohistochemical evidence of COX-2 and PDGF-B levels were observed early (i.e. Day 3) and decreased rapidly by Day 7. BMP-6 expression was maximal at Day 3 and slowly declined by Day 28. In contrast, IGF-I/II expression gradually increased during the 28-day period. Systemic administration NS-398 caused a statistically significant reduction (P<0.05) in new bone formation (25-30%) and was associated with a statistically significant reduction in BMP-6 protein and mRNA expression (50% and 65% at P<0.05 and P<0.01, respectively). PDGF-B mRNA or protein expression was not affected by NS-398 treatment.

CONCLUSION

COX-2 inhibition resulted in reduced BMP-6 expression and impaired osseous regeneration suggesting an important role for COX-2-induced signaling in BMP synthesis and new bone formation.

A Comparative Study of Bilateral Sinus Lifts Performed with Platelet-Rich Plasma Alone Versus Alloplastic Graft Material Reconstituted with Blood

The objective of this study was to compare the alveolar bone growth in the 2 sides of the maxillary sinus after bilateral sinus lift procedures were performed with the simultaneous placement of dental implants in 20 consecutive patients. After elevation of the Schneiderian membrane, one side had only platelet-rich plasma (PRP) gel applied, while the other had placed only alloplastic graft material reconstituted with blood. Both open window and closed window techniques were used in ridges with > or =9 mm residual crest of bone. Results indicate that using PRP alone in cases with >7 mm residual crest can produce bone growth. Preliminary results indicate that in cases with a minimum of 7-mm crestal bone, it is possible to use a crestal approach for sinus grafting, with PRP alone and implant placement for bone growth.

Guided bone regeneration membrane made of polycaprolactone/calcium carbonate composite nano-fibers

In this study, new type of guided bone regeneration (GBR) membranes were fabricated by polycaprolactone (PCL)/CaCO3 composite nano-fibers with two different PCL to calcium carbonate (CaCO3) ratios (PCL:CaCO3=75:25 wt% and 25:75 wt%). The composite nano-fibers were successfully fabricated by electrospinning method and CaCO3 nano-particles on the surface of nano-fibers were confirmed by energy disperse X-ray (EDX) analysis. In order to achieve mechanical stability of GBR membranes, composite nano-fibers were spun on PCL nano-fibrous membranes which has high tensile strength, i.e., the membranes consist of two layers of functional layer (PCL/CaCO3) and mechanical support layer (PCL). Two different GBR membranes were prepared, i.e., GBR membrane (A)=PCL:CaCO3=75:25 wt%+PCL, GBR membrane (B)=PCL:CaCO3=25:75 wt%+PCL. Osteoblast attachment and proliferation of GBR membrane (A) and (B) were discussed by MTS assay and scanning electron microscope (SEM) observation. As a result, absorbance intensity of GBR membrane (A) and tissue culture polystyrene (TCPS) increased during 5 days seeding time. In contrast, although absorbance intensity of GBR membrane (B) also increased, its value was lower than membrane (A). SEM observation showed that no significant difference in osteoblast attachment manner was seen on GBR membrane (A) and (B). Because of good cell attachment manner, there is a potential to utilize PCL/CaCO3 composite nano-fibers to GBR membranes.

Development of guided bone regeneration membrane composed of beta-tricalcium phosphate and poly (L-lactide-co-glycolide-co-epsilon-caprolactone) composites

To create biodegradable and thermoplastic materials for guided bone regeneration, GBR, and guided tissue regeneration, GTR, membranes, composites of beta-tricalcium phosphate, TCP, and biodegradable polyesters, poly (L-lactide-co-glycolide-co-epsilon-caprolactone), PLGC, and poly (L-lactide-co-epsilon-caprolactone), PLCL, were prepared by a heat-kneading method. The composites maintained thermoplasticity and mechanical strength by formation of a chemical interaction between Ca on TCP and C=O on the lactide segment of PLGC or PLCL. The composites also indicated composite effects in pH auto-regulation property and elongation of biodegradation period, e.g., the composites maintained their mechanical strength up to 12 weeks after soaking in both physiological and phosphate-buffered saline, and the period was sufficient time to use for GBR and GTR membranes. Animal tests for GBR indicated that the present composite membrane successfully regenerated beagles' mandible defects 10 x 10 x 10 mm3 in size. These results suggested that the TCP/PLGC bioresorbable composites could be utilized for GBR and GTR therapy.

The growth improvement of porcine esophageal smooth muscle cells on collagen-grafted poly(DL-lactide-co-glycolide) membrane

Synthetic polyester and the extracellular matrix component collagen are among the most widely used materials in tissue engineering. However, the integration of collagen into polyester scaffolds without loss of its biological function is a problem that has not been fully solved. This article investigates the covalent immobilization of collagen onto poly(DL-Lactide-co-Glycolide) (PLGA) membrane surfaces via a bridge of 1,8-diaminooctane and with glutaraldehyde as crosslinking agent. X-ray photoelectron spectroscopy (XPS) and fluorescence measurements confirmed the presence of bonded collagen. The effect of collagen grafting on cell behavior was investigated by comparing collagen-PLGA with unmodified PLGA sample and tissue culture polystyrene (TCPS) plates by using porcine esophageal smooth muscle cells (ESMC). DNA analysis showed that collagen-modified PLGA improved the overall proliferation of the ESMCs compared with unmodified PLGA and TCPS plates. Cells seeded on collagen-modified PLGA also showed a more extended morphology. Thus, we believe that collagen-modified PLGA shows good potential to be used as a scaffold material for tissue engineering of the esophagus.

Chitin/PLGA blend microspheres as a biodegradable drug delivery system: a new delivery system for protein

Novel chitin/PLGAs and chitin/PLA based microspheres were developed for the delivery of protein. These biodegradable microspheres were prepared by polymers blending and wet phase-inversion methods. The parameters such as selected non-solvents, temperature of water and ratio of polylactide to polyglycolide were adjusted to improve thermodynamic compatibility of individual polymer (chitin and PLGAs or chitin/PLA), which affects the hydration and degradation properties of the blend microspheres. Triphasic pattern of drug release model is observed from the release of protein from the chitin/PLGAs and chitin/PLA microspheres: the initially fast release (the first phase), the following slow release (the second phase) and the second burst release (the third phase). Formulations of the blends, which are based on the balance among the hydration rate of the chitin phase and degradation of chitin/PLA and PLGA phase, can lead to a controllable release of bovine serum albumin (BSA). In conclusion, such a chitin/PLGA 50/50 microsphere is novel and interesting, and may be used as a protein delivery system.