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

In vivo evaluation of bone regeneration using ZIF8-modified polypropylene membrane in rat calvarium defects

AIM

The profound potential of zeolitic imidazolate framework 8 (ZIF8) thin film for inducing osteogenesis has been previously established under in vitro conditions. As the next step towards the clinical application of ZIF8-modified substrates in periodontology, this in vivo study aimed to evaluate the ability of the ZIF8 crystalline layer to induce bone regeneration in an animal model defect.

MATERIALS AND METHODS

Following the mechanical characterization of the membranes and analysing the in vitro degradation of the ZIF8 layer, in vivo bone regeneration was evaluated in a critical-sized (5-mm) rat calvarial bone defect model. For each animal, one defect was randomly covered with either a polypropylene (PP) or a ZIF8-modified membrane (n = 7 per group), while the other defect was left untreated as a control. Eight weeks post surgery, bone formation was assessed by microcomputed tomography scanning, haematoxylin and eosin staining and immunohistochemical analysis.

RESULTS

The ZIF8-modified membrane outperformed the PP membrane in terms of mechanical properties and revealed a trace Zn+2 release. Results of in vivo evaluation verified the superior barrier function of the ZIF8-coated membrane compared with pristine PP membrane. Compared with the limited marginal bone formation in the control and PP groups, the defect area was almost filled with mature bone in the ZIF8-coated membrane group.

CONCLUSIONS

Our results support the effectiveness of the ZIF8-coated membrane as a promising material for improving clinical outcomes of guided bone regeneration procedures, without using biological components.

Dopamine-Assisted Modification of Polypropylene Film to Attain Hydrophilic Mineral-Rich Surfaces

The presented study focuses on the modification of polypropylene (PP) film with tetraethyl orthosilicate (TEOS) under heterogeneous conditions via polydopamine/polyethylene imine (PDA/PEI) chemistry using a facile dip-coating procedure to attain hydrophilic mineral-rich surfaces. Thus, the resulting PP-based films were further immersed in ion-rich simulated body fluid (SBF) to deposit Ca-based minerals onto the film's surfaces efficiently. In addition, the chemical reaction mechanism on PP film was proposed, and mineralisation potential inspected by determination of functional groups of deposits, zeta potential, hydrophilicity and surface morphology/topography using Fourier transform infrared (FTIR) spectroscopy, streaming potential, water contact angle (WCA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The obtained results show the improved wettability of samples on account of PDA inclusion (WCA was reduced from 103° for pure PP film to 28° for PDA-modified film), as well as the presence of functional groups, due to the PDA/PEI/TEOS surface functionalisation, increased the ability of minerals to nucleate on the PP film's surface when it was exposed to an SBF medium. Moreover, the higher surface roughness due to the silica coatings influenced the enhanced anchoring and attachment of calcium phosphate (CaP), revealing the potential of such a facile approach to modify the chemically inert PP films, being of particular interest in different fields, including regenerative medicine.

Histological Evaluation of Guided Bone Regeneration in Osseous Defects Using A Novel Non-Resorbable Membrane

BACKGROUND: Guided bone regeneration and guided tissue regeneration procedures have been performed using barrier membranes in clinical dentistry to enhance bone formation in osseous defects, ridge preservation and reconstruction. Despite the considerable number of new biomaterials that develop with more advantages and fewer disadvantages for bone regeneration, the cost and surgical approach difficulties are still the main obstacles that we tried to overcome using the novel membrane. AIM: Our research aimed to assess histologically the bone formation using the novel membrane in experimental bone defects. MATERIAL AND METHODS: Our study was conducted on ten mongrel dogs. Each animal presented two groups. The first group was at the left side of the animal mandible which received Bio-Oss only while the right side received Bio-Oss and was covered by the novel non-resorbable membrane. These dogs were sacrificed (3, 6, 9 and 12 weeks) postoperatively for histological assessment of healing and bone formation of osseous defects. RESULTS: The histological evaluation showed that the formation of new bone in group I (Bio-OSS only) was less in amount as compared with group II (Bio-Oss with the novel non-resorbable membrane). CONCLUSION: The present clinical findings revealed that the novel non-resorbable membrane was inert and induced no inflammatory reaction or graft rejection. The study provided histological evidence of new bone formation in close contact with host bone due to osteoconductivity of Bio-Oss and cell occlussiveness of the membrane.

The Masquelet Technique: Can Disposable Polypropylene Syringes be an Alternative to Standard PMMA Spacers? A Rat Bone Defect Model

BACKGROUND

Usually, the two-stage Masquelet induced-membrane technique for extremity reconstruction begins with a polymethylmethacrylate (PMMA) cement spacer-driven membrane, followed by an autologous cancellous bone graft implanted into the membrane cavity to promote healing of large bone defects. In exceptional cases, spacers made of polypropylene disposable syringes were successfully used instead of the usual PMMA spacers because of a PMMA cement shortage caused by a lack of resources. However, this approach lacks clinical evidence and requires experimental validation before being recommended as an alternative to the conventional technique.

QUESTIONS/PURPOSES

To (1) develop and (2) validate a critical-sized femoral defect model in rats for two stages of the Masquelet technique and to (3) compare the biological and bone healing properties of polypropylene-induced membranes and PMMA-induced membranes in this model.

METHODS

Fifty male Sprague Dawley rats aged 8 weeks old received a 6-mm femur defect, which was stabilized with an external fixator that was converted into an internal device. In the development phase, the defect was filled with PMMA in 16 rats to determine the most favorable timing for bone grafting. Two rats were excluded since they died of anesthetic complications. The other 14 were successively euthanized after 2 weeks (n = 3), 4 weeks (n = 4), 6 weeks (n = 4), and 8 weeks (n = 3) for induced membrane analyses. In the validation phase, 12 rats underwent both stages of the procedure using a PMMA spacer and were randomly assigned to two groups, whether the induced membrane was preserved or removed before grafting. To address our final objective, we implanted either polypropylene or PMMA spacers into the defect (Masquelet technique Stage 1; n = 11 rats per group) for the period established by the development phase. In each group, 6 of 11 rats were euthanized to compare the biological properties of polypropylene-induced membranes and PMMA-induced membranes using histological qualitative analysis, semiquantitative assessment of the bone morphogenic protein-2 content by immunostaining, and qualitative assessment of the mesenchymal stromal cell (MSC; CD31-, CD45-, CD90+, and CD73+ phenotypes) content by flow cytometry. Quantitative measurements from serum bone turnover markers were also performed. The five remaining rats of each group were used for Masquelet technique Stage 2, in which rat bone allografts were implanted in the induced membrane cavity after the polypropylene or PMMA spacers were removed. These rats recovered for 10 weeks before being euthanized for microCT quantitative measurements and bone histology qualitative assessment to evaluate and compare the extent of bone regeneration between groups.

RESULTS

Induced membrane analyses together with serum bone turnover measurements indicated that a 4-week interval time between stages was the most favorable. Removal of the induced membrane before grafting led to almost constant early implant failures with poor bone formation. Four-week-old rats with polypropylene-triggered induced membranes displayed similar histologic organization as rats with PMMA-driven induced membranes, without any difference in the cell density of the extracellular matrix (4933 ± 916 cells per mm2 for polypropylene versus 4923 ± 1284 cells per mm2 for PMMA; p = 0.98). Induced membrane-derived MSCs were found in both groups with no difference (4 of 5 with polypropylene versus 3 of 3 with PMMA; p > 0.99). Induced membrane bone morphogenic protein-2 immunolabeling and serum bone turnover marker levels were comparable between the polypropylene and PMMA groups. MicroCT analysis found that bone regeneration in the polypropylene group seemed comparable with that in the PMMA group (29 ± 26 mm3 for polypropylene versus 24 ± 18 mm3 for PMMA; p > 0.99). Finally, qualitative histological assessment revealed a satisfactory endochondral ossification maturation in both groups.

CONCLUSION

Using a critical-sized femoral defect model in rats, we demonstrated that polypropylene spacers could induce membrane encapsulation with histologic characteristics and bone regenerative capacities that seem like those of PMMA spacers.

CLINICAL RELEVANCE

In a same bone site, polymers with close physical properties seem to lead to similar foreign body reactions and induce encapsulating membranes with comparable bone healing properties. Polypropylene spacers made from disposable syringes could be a valuable alternative to PMMA. These results support the possibility of a cementless Masquelet technique in cases of PMMA shortage caused by a lack of resources.

ZIF-8 Modified Polypropylene Membrane: A Biomimetic Cell Culture Platform with a View to the Improvement of Guided Bone Regeneration

PURPOSE

Despite the significant advances in modeling of biomechanical aspects of cell microenvironment, it remains a major challenge to precisely mimic the physiological condition of the particular cell niche. Here, the metal-organic frameworks (MOFs) have been introduced as a feasible platform for multifactorial control of cell-substrate interaction, given the wide range of physical and mechanical properties of MOF materials and their structural flexibility.

RESULTS

In situ crystallization of zeolitic imidazolate framework-8 (ZIF-8) on the polydopamine (PDA)-modified membrane significantly raised surface energy, wettability, roughness, and stiffness of the substrate. This modulation led to an almost twofold increment in the primary attachment of dental pulp stem cells (DPSCs) compare to conventional plastic culture dishes. The findings indicate that polypropylene (PP) membrane modified by PDA/ZIF-8 coating effectively supports the growth and proliferation of DPSCs at a substantial rate. Further analysis also displayed the exaggerated multilineage differentiation of DPSCs with amplified level of autocrine cell fate determination signals, like BSP1, BMP2, PPARG, FABP4, ACAN, and COL2A. Notably, osteogenic markers were dramatically overexpressed (more than 100-folds rather than tissue culture plate) in response to biomechanical characteristics of the ZIF-8 layer.

CONCLUSION

Hence, surface modification of cell culture platforms with MOF nanostructures proposed as a powerful nanomedical approach for selectively guiding stem cells for tissue regeneration. In particular, PP/PDA/ZIF-8 membrane presented ideal characteristics for using as a barrier membrane for guided bone regeneration (GBR) in periodontal tissue engineering.