Early biocompatibility of poly (ethylene glycol) hydrogel barrier materials for guided bone regeneration. An in vitro study using human gingival fibroblasts (HGF-1)

Durability of Implanted Low-Density Polyacrylamide Hydrogel Used as a Scaffold for Microencapsulated Molecular Probes inside Small Fish

Implantable sensors based on shaped biocompatible hydrogels are now being extensively developed for various physiological tasks, but they are usually difficult to implant into small animals. In this study, we tested the long-term in vivo functionality of pH-sensitive implants based on amorphous 2.7% polyacrylamide hydrogel with the microencapsulated fluorescent probe SNARF-1. The sensor was easy to manufacture and introduce into the tissues of a small fish Danio rerio, which is the common model object in biomedical research. Histological examination revealed partial degradation of the gel by the 7th day after injection, but it was not the case on the 1st day. Using the hydrogel sensor, we were able to trace the interstitial pH in the fish muscles under normal and hypercapnic conditions for at least two days after the implantation. Thus, despite later immune response, amorphous polyacrylamide is fully suitable for preparing implantable sensors for various mid-term physiological experiments on small fishes. The proposed approach can be further developed to create implantable sensors for animals with similar anatomy.

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

Regenerative medicine is becoming a rapidly evolving technique in today’s biomedical progress scenario. Scientists around the world suggest the use of naturally synthesized biomaterials to repair and heal damaged cells. Hydroxyapatite (HAp) has the potential to replace drugs in biomedical engineering and regenerative drugs. HAp is easily biodegradable, biocompatible, and correlated with macromolecules, which facilitates their incorporation into inorganic materials. This review article provides extensive knowledge on HAp and collagen-containing compositions modified with drugs, bioactive components, metals, and selected nanoparticles. Such compositions consisting of HAp and collagen modified with various additives are used in a variety of biomedical applications such as bone tissue engineering, vascular transplantation, cartilage, and other implantable biomedical devices.

Biodegradation and tissue integration of various polyethylene glycol matrices: a comparative study in rabbits

OBJECTIVES

To test whether or not chemical and/or physical modifications of polyethylene glycol (PEG) hydrogels influence degradation time, matrix/membrane stability, and integration into surrounding hard and soft tissues.

MATERIAL AND METHODS

In 28 rabbits, six treatment modalities were randomly applied to six sites on the rabbit skull: a dense network PEG hydrogel (PEG HD), a medium-dense network PEG hydrogel (PEG MD), a medium-dense network PEG hydrogel modified with an RGD sequence (PEG MD/RGD), a medium-dense network PEG hydrogel modified with RGD with reduced carboxymethyl cellulose (PEG MD/RGD_LV), a loose network PEG hydrogel modified with RGD (PEG LD/RGD), and a collagen membrane (BG). Descriptive histology and histomorphometry were performed at 1, 2, 4, and 6 weeks.

RESULTS

PEG HD revealed the highest percentage of residual matrix at all time points starting with 47.2% (95% CI: 32.8-63.8%) at 1 week and ending with 23.4% (95% CI: 10.3-49.8%) at 6 weeks. The hydrogel with the loosest network (PEG LD/RGD) was stable the first 2 weeks and then degraded continuously with a final area of 8.3% (95% CI: 3.2-21.2%). PEG HD was the most stable and densely stained membrane, whereas PEG MD and PEG LD matrices integrated faster, but started to degrade to a higher degree between 2 and 4 weeks. PEG MD degradation was dependent on the addition of RGD and the amount of CMC.

CONCLUSIONS

Chemical and/or physical modifications of PEG hydrogels influenced matrix stability. PEG MD/RGD demonstrated an optimal balance between degradation time and integration into the surrounding soft and hard tissues.

Drug loaded poly(glycerol sebacate) as a local drug delivery system for the treatment of periodontal disease

A simple, cost-efficient method to load drugs into poly(glycerol sebacate) polymer. Drugs were able to sustained release for up to 60 days. The drugs loaded polymer showed cytocompatibility and antimicrobial activities.

Clinoptilolite/PCL–PEG–PCL composite scaffolds for bone tissue engineering applications

The aim of this study was to prepare and characterize highly porous clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) composite scaffolds. Scaffolds with different clinoptilolite contents (10% and 20%) were fabricated with reproducible solvent-free powder compression/particulate leaching technique. The scaffolds had interconnective porosity in the range of 55–76%. Clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) scaffolds showed negligible degradation within eight weeks and displayed less water uptake and higher bioactivity than poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) scaffolds. The presence of clinoptilolite improved the mechanical properties. Highest compressive strength (5.6 MPa) and modulus (114.84 MPa) were reached with scaffold group containing 20% clinoptilolite. In vitro protein adsorption capacity of the scaffolds was also higher for clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) scaffolds. These scaffolds had 0.95 mg protein/g scaffold adsorption capacity and also higher osteoinductivity in terms of enhanced ALP, OSP activities and intracellular calcium deposition. Stoichiometric apatite deposition (Ca/P=1.686) was observed during cellular proliferation analysis with human fetal osteoblasts cells. Thus, it can be suggested that clinoptilolite/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) composite scaffolds could be promising carriers for enhancement of bone regeneration in bone tissue engineering applications.

Bone augmentation at peri-implant dehiscence defects comparing a synthetic polyethylene glycol hydrogel matrix vs. standard guided bone regeneration techniques

OBJECTIVES

The aim of the study was to test whether or not the use of a polyethylene glycol (PEG) hydrogel with or without the addition of an arginylglycylaspartic acid (RGD) sequence applied as a matrix in combination with hydroxyapatite/tricalciumphosphate (HA/TCP) results in similar peri-implant bone regeneration as traditional guided bone regeneration procedures.

MATERIAL AND METHODS

In 12 beagle dogs, implant placement and peri-implant bone regeneration were performed 2 months after tooth extraction in the maxilla. Two standardized box-shaped defects were bilaterally created, and dental implants were placed in the center of the defects with a dehiscence of 4 mm. Four treatment modalities were randomly applied: i)HA/TCP mixed with a synthetic PEG hydrogel, ii)HA/TCP mixed with a synthetic PEG hydrogel supplemented with an RGD sequence, iii)HA/TCP covered with a native collagen membrane (CM), iv)and no bone augmentation (empty). After a healing period of 8 or 16 weeks, micro-CT and histological analyses were performed.

RESULTS

Histomorphometric analysis revealed a greater relative augmented area for groups with bone augmentation (43.3%-53.9% at 8 weeks, 31.2%-42.8% at 16 weeks) compared to empty controls (22.9% at 8 weeks, 1.1% at 16 weeks). The median amount of newly formed bone was greatest in group CM at both time-points. Regarding the first bone-to-implant contact, CM was statistically significantly superior to all other groups at 8 weeks.

CONCLUSIONS

Bone can partially be regenerated at peri-implant buccal dehiscence defects using traditional guided bone regeneration techniques. The use of a PEG hydrogel applied as a matrix mixed with a synthetic bone substitute material might lack a sufficient stability over time for this kind of defect.

Mesoporous bioactive glass surface modified poly(lactic-co-glycolic acid) electrospun fibrous scaffold for bone regeneration

A mesoporous bioactive glass (MBG) surface modified with poly(lactic-co-glycolic acid) (PLGA) electrospun fibrous scaffold for bone regeneration was prepared by dip-coating a PLGA electrospun fibrous scaffold into MBG precursor solution. Different surface structures and properties were acquired by different coating times. Surface morphology, chemical composition, microstructure, pore size distribution, and hydrophilicity of the PLGA-MBG scaffold were characterized. Results of scanning electron microscopy indicated that MBG surface coating made the scaffold rougher with the increase of MBG content. Scaffolds after MBG modification possessed mesoporous architecture on the surface. The measurements of the water contact angles suggested that the incorporation of MBG into the PLGA scaffold improved the surface hydrophilicity. An energy dispersive spectrometer evidenced that calcium-deficient carbonated hydroxyapatite formed on the PLGA-MBG scaffolds after a 7-day immersion in simulated body fluid. In vitro studies showed that the incorporation of MBG favored cell proliferation and osteogenic differentiation of human mesenchymal stem cells on the PLGA scaffolds. Moreover, the MBG surface-modified PLGA (PLGA-MBG) scaffolds were shown to be capable of providing the improved adsorption/release behaviors of bone morphogenetic protein-2 (BMP-2). It is very significant that PLGA-MBG scaffolds could be effective for BMP-2 delivery and bone regeneration.

The efficacy of BMP-2 preloaded on bone substitute or hydrogel for bone regeneration at peri-implant defects in dogs

OBJECTIVES

The objective of this experiment was to test whether or not a synthetic bone substitute (SBS) was more effective than a polyethylene glycol hydrogel as a carrier material for bone morphogenetic protein-2 (BMP-2) when attempting to regenerate bone.

MATERIAL AND METHODS

Two identical, box-type dehiscence defects (4 × 4 mm buccolingually and apicocoronally, and 8 mm mesiodistally) were surgically prepared on buccal sides of the left and right edentulous ridge in five beagle dogs. Following implant placement, the defects either received (i) no graft, (ii) SBS+hydrogel, (iii) SBS+BMP-2 loaded hydrogel, and (iv) BMP-2-loaded SBS+hydrogel. The animals were euthanized at 8 weeks postsurgery. Radiographic and histomorphometric analyses were performed.

RESULTS

The hydrogel alone was not able to stabilize the grafted bone particles at 8 weeks, and SBS+hydrogel group did not significantly differ from the control group in all volumetric measurements. On the other hand, extensively regenerated new bone was connected with most of the remaining SBS particles in the BMP-2 groups. The BMP-2 groups exhibited significantly greater new bone formation (10.65 mm(3) and 1.47 mm(2) in the SBS+BMP-2-loaded hydrogel group; 14.17 mm(3) and 0.93 mm(2) in the BMP-2-loaded SBS+hydrogel) than non-BMP-2 groups (1.27 mm(3) and 0.00 mm(2) in the control group; 2.01 mm(3) and 0.19 mm(2) in the SBS+hydrogel group) in volumetric and histomorphometric analyses (P < 0.001). However, there were no significant differences between both BMP-2 groups.

CONCLUSION

BMP-2 could yield enhanced bone regeneration in the critical-size peri-implant defects regardless of whether SBS or hydrogel is used for preloading, although the outcomes seem to be more reproducible with BMP-2 preloaded on SBS.

Evaluation of a Polyethylene Glycol-Osteogenic Protein-1 System on Alveolar Bone Regeneration in the Mini-Pig

Alveolar bone regeneration associated with the local release of osteogenic protein-1 (OP-1) from a polyethylene glycol (PEG) scaffold was evaluated in 14 mini-pigs. Following extraction of mandibular teeth and 26-weeks of healing time, standardized bone defects were created bilaterally in the posterior mandibles (3 sites for each hemimandible) that were randomly assigned to treatment groups. Seven treatments groups were compared: 4 different concentrations of the PEG/OP-1 test system (n = 14 for each), a positive control (collagen/OP-1, n = 14), a negative control (PEG only, n = 7) and nontreated defects (n = 7). Each animal provided all test and control groups. The animals were sacrificed after 3 weeks of healing and samples were processed for histology and histomorphometry. Three weeks after implantation, there were positive clinical responses for all test groups. Earlier bone maturation was observed in the test groups that had higher concentrations of OP-1 (0.25, 0.5, or 1 mg/mL) compared to the negative control group (PEG alone), the low concentration group (0.1 mg/mL), and the positive control group (collagen/OP-1). However, histomorphometric quantitative analyses did not reveal any statistical difference between any of the groups. No residual PEG biomaterial or inflammatory responses to the biomaterial or growth factor were observed. This study confirmed the safe local delivery of OP-1 from PEG hydrogel. Alveolar bone regeneration was not statistically different between tests groups, negative control (PEG alone) or commercial positive control (collagen/OP-1). The semi-quantitative analysis, however, showed a trend in favor of the higher concentrations of OP-1 to induce faster bone maturation.