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PubMed2003

Biopolymers and biodegradable smart implants for tissue regeneration after spinal cord injury.

PURPOSE OF REVIEW: This article reviews recent experimental advances in the development of biosynthetic implants for repair of spinal cord injury. RECENT FINDINGS: Various important advances in the development of biosynthetic conduits for spinal cord repair have recently been reported. It was found that implantation of freeze dried alginate sponge into completely transected spinal cord supports axonal regeneration across the lesion site. A poly(lactic-co-glycolic acid) scaffold seeded with neural stem cells has been developed that promotes axonal regeneration across the gap. It was found that polyethylene glycol can reseal damaged spinal cord axons and restore impulse conduction. Findings have been reported that poly-beta-hydroxybutyrate conduits in combination with alginate and fibronectin provide neuroprotection for axotomized descending neurones. It has been reported that conduits made of fibronectin mats or fibrin in combination with neurotrophic growth factors promote axonal growth into the grafts. Finally, magnetic resonance imaging after experimental spinal cord injury has been used to monitor regeneration in biosynthetic conduits in vivo over time. SUMMARY: Biosynthetic conduits carrying extracellular matrix molecules and different cell lines, and supplemented with neurotrophic growth factors have yielded encouraging results in the treatment of experimental spinal cord injury. These findings provide a basis for further development of techniques aimed at spinal cord repair in humans.

Absorbable Implants↗

PubMed2005

[Cell proliferation and cellular activity of primary cell cultures of the oral cavity after cell seeding on the surface of a degradable, thermoplastic block copolymer].

Using standard cell biological and biochemical methods we were able to test the ability of a degradable, thermoplastic block copolymer to support the adhesion, proliferation, and the cellular activity of primary cell cultures of the oral cavity in vitro. The delicate balance between a group of endogenous enzymes, Matrix Metalloproteinases (MMPs), and their inhibitors (Tissue Inhibitor of MMPs, TIMPs) have a decisive function in the remodeling of the extracellular matrix during processes like wound healing or the integration of biomaterials in surrounding tissues after implantation. Recently developed, biodegradable thermoplastic elastomers with shape-memory properties may be the key to develop new therapeutical options in head and neck surgery. Primary cell cultures of the oral cavity of Sprague-Dawley rats were seeded on the surface of a thermoplastic block copolymer and on a polystyrene surface as control. Conditioned media of the primary cells were analyzed for MMPs and TIMPs after different periods of cell growth. The MMP and TIMP expression was analysed by zymography and a radiometric enzyme assay. No statistically significant differences in the appearance and the kinetic of MMP-1, MMP-2, MMP-9 and TIMPs were detected between cells grown on the polymer surface compared to the control. An appropriate understanding of the molecular processes that regulate cellular growth and integration of a biomaterial in surrounding tissue is the requirement for an optimal adaptation of biodegradable, polymeric biomaterials to the physiological, anatomical, and surgical conditions in vivo to develop new therapeutic options in otolaryngology and head and neck surgery.

Absorbable Implants↗

PubMed2004

Pharmacological effects of melatonin on reproductive activity: experimental bioimplants with sustained-release polymeric systems.

A vast literature documents the role of melatonin in human reproductive function including: a) the relation between melatonin and the menstrual cycle in relation to the peak time of luteinizing hormone in the middle of the cycle; b) the varying concentrations of melatonin in the control of puberty; c) the fewer conceptions in some artic populations where melatonin is connected significantly to seasonal photoperiodicity during the months of the polar nights. The aim of this paper is to report our findings on the pharmacological action of this molecule on reproduction in which gonadal activity is clearly connected to photoperiodicity. We used polymer bioimplants programmed for the sustained release of melatonin for experimental gynecologic protocols. These implants had beneficial results with respect to the use of progestinics because melatonin allowed ovarian activity to be induced for at least two to three consecutive cycles with one single bioimplant. We thought it indispensable to use pharmacological systems with a sustained release because different preliminary tests showed that the half-life of melatonin is limited at maximum to two to three hours and, consequently, any other tested modalities of administration would not provide any appreciable results for our study. As a model for our research we used goats to administer melatonin via targeted programs since these animals clearly respond (even against the rule of the light/dark relation) in contrast to humans in whom response is less evident. For controls, after inserting bioimplants in the animals, we tested their efficiency in vitro and subsequently in vivo, evaluating blood parameters and pharmacological effects of melatonin occurring during the treatment. The final results proved to be interesting in relation to reproductive activity in that regular and programmed births were achieved.

Absorbable Implants↗

PubMed2005

Plasma transglutaminase factor XIII induces microvessel ingrowth into biodegradable hydroxyapatite implants in rats.

Coagulation factor XIII is a member of the transglutaminase-family. Transgluaminases cross-link either fibrin monomers in blood coagulation or extracellular proteins in extracellular matrix formation. In early stages of bone healing migration and proliferation of endothelial cells lead to formation of new vessels. The aim of this study was to investigate the angiogenetic activity of plasma factor XIII in bone defects filled with nanoparticulate hydroxyapatite paste. A critical size defect was created in the tibial head of rats which was not filled in group I. In group II the defect was filled with hydroxyapatite paste, and in group III with hydroxyapatite paste enriched with factor XIII. Ten days after surgery angiogenesis in the defects was assessed using immunohistochemistry and confocal laser scanning microscopy. Ac16 antibody was used to detect activation of factor XIII into factor XIIIA. In defects without biomaterial (group I) vessel-rich connective tissue and diffuse distribution of capillaries was observed. In defects filled with pure hydroxyapatite (group II) formation of capillaries was limited to the host bone-hydroxyapatite interface. In contrast, addition of plasma factor XIII to hydroxyapatite (group III) stimulated formation of vessels within the biomaterial. The current study reveals that factor XIII can improve angiogenesis in hydroxyapatite.

Absorbable Implants↗

PubMed2006

Development and characterization of interleukin-18-loaded biodegradable microspheres.

Immunostimulation represents a promising approach designed to specifically eradicate malignant cells. Since glioma tumour cells hole up in the central nervous system (CNS) in a particularly inauspicious milieu to antitumour immune reactions we here propose a new strategy to revert the properties of this microenvironment by administering an antitumour cytokine into the CNS tumour itself. Thus, biodegradable poly(D,L-lactide-co-glycolide) (PLGA) sustained-release microspheres for stereotaxic implantation loaded with interleukin-18 (IL-18), that is known to exert antitumour activity and trigger immune cell-mediated cytotoxicity, were developed. Different tests for assessing IL-18 bioactivity were set-up and evaluated. A specific bioassay was considered as the most reliable test. The stability and integrity of IL-18 was then verified during the encapsulation process. Consequently, two procedures of IL-18 encapsulation in PLGA microparticles (W/O/W and S/O/W) were investigated. As determined by radiolabelling studies using 125I-IL-18 and a continuous flow system, the in vitro release profile of IL-18 was optimum with S/O/W method with a moderate burst effect and a subsequent progressive discharge of 16.5+/-8.4 ng/day during the next 21 days against 6.1+/-4.2 ng/day with the W/O/W method. Considering analytical testing of IL-18 together with its preserved biological activity after release from microspheres, amounts of the active cytokine obtained with S/O/W method were relevant to plan in vivo evaluation to validate the therapeutic strategy.

Absorbable Implants↗

PubMed1998

Degradation of and intraosseous reactions to biodegradable poly-L-lactide screws: a study in minipigs.

In 20 minipigs an osteotomy of the lumbar spine was done at L3 and fixed with resorbable implants (plate and screws) made of poly-L-lactide. For 24 months postoperatively the cancellous bone surrounding the screws was examined histologically. Specimens from the body of lumbar spine L2 and L4, carrying the screws, were fixed in a series of ethanol immersions and then embedded in methylmethacrylate. Longitudinal and transverse sections were cut with a microtome at 4-5 microns and stained by the Masson-Goldner and Giemsa method for light microscopy. Our investigation confirmed a long degradation period of poly-L-lactide and little inflammatory reaction within the bone during the whole period of observation. For poly-L-lactide the degradation time exceeded the longest follow-up time in this study, 24 months. Polymorphonuclear granulocytes and mononuclear round cells were scarce in all follow-up groups. Osteolytic changes or the emergence of seroma was not observed. Textured bone was evident early close to a thin fibrous capsule surrounding the screws. The remodelling of the bone close to the screws ensues by the formation of osteons.

Absorbable Implants↗

PubMed2004

Tissue-engineered trachea from sheep marrow stromal cells with transforming growth factor beta2 released from biodegradable microspheres in a nude rat recipient.

OBJECTIVE: The purpose of this study was to evaluate the feasibility of using autologous sheep marrow stromal cells cultured onto polyglycolic acid mesh to develop helical engineered cartilage equivalents for a functional tracheal replacement. We also explored the potential benefit of local delivery of transforming growth factor beta 2 with biodegradable gelatin microspheres. METHODS: Bone marrow was obtained by iliac crest aspiration from 6-month-old sheep and cultured in monolayer for 2 weeks. At confluence, the cells were seeded onto nonwoven polyglycolic acid fiber mesh and cultured in vitro with transforming growth factor beta 2 and insulin-like growth factor 1 for 1 week. Cell-polymer constructs were wrapped around a silicone helical template. Constructs were then coated with microspheres incorporating 0.5 microg transforming growth factor beta 2. The cell-polymer-microsphere structures were then implanted into a nude rat. On removal, glycosaminoglycan content and hydroxyproline were analyzed in both native and tissue-engineered trachea. Histologic sections of both native and tissue-engineered trachea were stained with hematoxylin and eosin, safranin-O, and a monoclonal anti-type II collagen antibody. RESULTS: Cell-polymer constructs with transforming growth factor beta 2 microspheres formed stiff cartilage de novo in the shape of a helix after 6 weeks. Control constructs lacking transforming growth factor beta 2 microspheres appeared to be much stiffer than typical cartilage, with an apparently mineralized matrix. Tissue-engineered trachea was similar to normal trachea. Histologic data showed the presence of mature cartilage. Glycosaminoglycan and hydroxyproline contents were also similar to native cartilage levels. CONCLUSIONS: This study demonstrates the feasibility of engineering tracheas with sheep marrow stromal cells as a cell source. Engineering the tracheal equivalents with supplemental transforming growth factor beta 2 seemed to have a positive effect on retaining a cartilaginous phenotype in the newly forming tissue.

Absorbable Implants↗

PubMed2001

Tissue reactions to particles of bone-substitute materials in intraosseous and heterotopic sites in rats: discrimination of osteoinduction, osteocompatibility, and inflammation.

Two rat models were used to characterize tissue-specific reactions to particles of bone-substitute materials: one for osteocompatibility in a healing tibial wound and the other in a heterotopic, subcutaneous site. Small, unicortical tibial wounds in rats healed spontaneously, beginning with the rapid proliferation of intramedullary woven bone. That temporary bone was resorbed by osteoclasts and finally, the cortical wound was healed with lamellar bone and the medullary space was repopulated with marrow. When various particulate materials were implanted into fresh wounds, three types of reactions were observed. (1) Demineralized bone powder (DBP) and non-resorbable calcium phosphate (nrCP) were incorporated into the reactive medullary and cortical bone. (2) Polymethylmetlhacrylate (PMMA) particles were surrounded with a fibrous layer, but did not impair bone healing. (3) Polyethylene (PE) shards and resorbable calcium phosphates (rCPs) were inflammatory and inhibited osseous repair. Subcutaneous sites showed osteoinductive, fibrotic, or inflammatory responses to these materials. Only DBP induced endochondral osteogenesis subcutaneously. The nrCP evoked a fibrous reaction. In contrast, rCPs, PMMA, and PE shards generated inflammatory reactions with each particle being surrounded by fibrous tissue and large multinucleated giant cells. In conclusion, only DBP showed osteoinductive as well as osteocompatible properties. The nrCP was osteocompatible. The rCPs stimulated various degrees of inflammatory responses. PMMA was osteocompatible and did not interfere with the bone healing process. PE was not osteocompatible and generated foreign body reactions in both sites. Use of the two sites distinguishes osteoinductive, osteocompatible, and inflammatory properties of particles of bone-substitute materials.

Absorbable Implants↗

PubMed2001

Failure strengths of suture vs. biodegradable arrow and staple for meniscal repair: an in vitro study.

A study was performed to determine the in vitro biomechanical behaviour of two 'all inside' meniscal repair techniques (Meniscal Arrow [Bionx Implants Inc.] and Meniscal Staple [Surgical Dynamics Inc.]) and compare these directly with both a horizontal and vertical suture repair. Using 30 fresh bovine medial menisci, vertical 'bucket handle' tears were created 4 mm from the meniscus periphery. Repairs were subsequently performed, using four techniques, with 15 repairs in each group, a horizontally placed 3-metric Ethibond suture, a vertically placed 3-metric Ethibond suture, a single 13-mm arrow and a single 7-mm staple. A tensile test was performed to determine the force at failure for each technique. The mean force at failure of the horizontal and vertical suture groups was 63.2 and 73.9 N, respectively, 44.3 N for the arrow group and 17.8 N for the staple group. The mean forces at failure were significantly different (P < 0.005). The mean tensile strength of the meniscal staple was significantly lower than that of both suture and arrow groups. The 7-mm staple design may not allow adequate interdigitation between the barbed legs and the semicircular collagen fibres of the meniscus.

Absorbable Implants↗

PubMed2005

Phospholipase A2 pathway association with macrophage-mediated polycarbonate-urethane biodegradation.

Activation of the phospholipase A2 (PLA2) pathway is a key cell signaling event in the inflammatory response. The PLA2 family consists of a group of enzymes that hydrolyze membrane phospholipids, resulting in the liberation of arachidonic acid (AA), a precursor to pro-inflammatory molecules. Given the well-documented activating role of biomaterials in the inflammatory response to medical implants, the present study investigated the link between PLA2 and polycarbonate-based polyurethane (PCNU) biodegradation, and the effect that material surface had on PLA2 activation in the U937 cell line. PCNUs were synthesized with poly(1,6-hexyl 1,2-ethyl carbonate)diol, 1,4-butanediol and one of two diisocyanates (hexane 1,6-diisocyanate or 4,4'-methylene bisphenyl diisocyanate) in varying stoichiometries and incubated with adherent U937 cells. PLA2 inhibiting agents resulted in significantly decreased PCNU biodegradation (p < 0.05). Moreover, when activation of PLA2 was assessed (3H-AA release), significantly more 3H-AA was released from PCNU-adherent U937 cells than polystyrene-adherent U937 cells (p < 0.05) which was significantly decreased in the presence of PLA2 inhibitors. The pattern of inhibition of U937 cell-mediated biodegradation and 3H-AA release that was modulated by PCNU surface differences, suggests a role for secretory PLA2 along with cytosolic PLA2. Understanding PCNU activation of intracellular pathways, such as PLA2, will allow the design of materials optimized for their intended use.

Absorbable Implants↗

PubMed2002

A biodegradable composite scaffold for cell transplantation.

Cell transplantation is rapidly becoming a therapeutic option to treat disease and injury. However, standard techniques for cell seeding on non-woven polymer meshes or within gels may not be suitable for immediate implantation or surgical manipulations of freshly isolated cells. Therefore, a biodegradable composite system was developed as a way to rapidly entrap cells within a support of predefined shape to potentially facilitate cell delivery into a target site (e.g. meniscal tears in the avascular zone). The composite construct consisted of freshly isolated cells, in this case pig chondrocytes, entrapped in a fibrin gel phase and dispersed throughout the void volume of a polyglycolic acid (PGA) non-woven mesh. Composites were cultured for up to 4 weeks. In vitro degradation of fibrin gel was evaluated via gel-entrapped urokinase. At 28 days in culture, glycosaminoglycan (GAG) content per cell in the composite scaffolds was 2.6 times that of the PGA-only cell construct group and 88% that of native pig cartilage. Total collagen content per cell in the composite scaffolds was not significantly different from the PGA-only cell construct group (P > 0.02) and represented 40% of the value determined for native cartilage. Varying the concentration of entrapped urokinase could effect controlled degradation of fibrin gel.

Absorbable Implants↗

PubMed2004

Biocompatible Nb2O5 thin films prepared by means of the sol-gel process.

Thin biocompatible oxide films with an optimised composition and structure on the surface of titanium and its alloys can improve the implant integration. The preparation of these thin oxide layers with the intended improvement of the surface properties can be realised by means of the sol-gel process. Nb2O5 is a promising coating material for this application because of its extremely high corrosion resistance and thermodynamic stability. In this study, thin Nb2O5 layers ( < 200 nm) were prepared by spin coating of polished discs of cp-titanium with a sol consisting of a mixture of niobium ethoxide, butanol and acetylacetone. The thickness, phase composition, corrosion resistance and the wettability of the oxide layers were determined after an optimisation of the processing parameters for deposition of oxide without any organic impurities. The purity of the oxide layer is an important aspect in order to avoid a negative response to the cell adhesion. The biocompatibility of the oxide layers which was investigated by in vitro tests (morphology, proliferation rate, WST-1, cell spreading) is improved as compared to uncoated and TiO2 sol-gel coated cp-titanium concerning the spreading of cells, collagen I synthesis and wettability.

3T3 Cells↗

PubMed2004

Bone formation and bioresorption after implantation of injectable beta-tricalcium phosphate granules-hyaluronate complex in rabbit bone defects.

The objective of this study was to evaluate the effects of a complex of beta-tricalcium phosphate (beta-TCP) granules and 3.5% hyaluronate (beta-TCP granules-HY complex) compared with a beta-TCP block, in terms of osteoconductivity and biodegradability, to determine whether this complex would be a good candidate for bone void filler. Both materials were implanted into cavities drilled in rabbit femoral condyles. New bone formation and mineral apposition rate were evaluated to analyze osteoconductivity, whereas residual beta-TCP within the defects and tartrate-resistant acid phosphatase (TRAP) cellular activity were studied for beta-TCP resorption. The results show that both the beta-TCP block and the beta-TCP granules-HY complex support bone ingrowth; however, bioresorption was rapid for beta-TCP granules-HY but weak for beta-TCP block. This biodegradation mechanism was considered to be a cell-mediated disintegration by numerous TRAP-positive giant cells. The time lag between the peak value of TRAP-positive giant cell population and that of new bone formation rate suggests that a coupling-like phenomenon could be occurring in the beta-TCP-filled bone defects. In addition, beta-TCP granules-HY complex, which is an injectable, pastelike material, has similar osteoconductive properties to beta-TCP block. Thus, this complex may be useful as a bone filler in clinical application.

Absorbable Implants↗

PubMed2005

Understanding the biodegradation of polyurethanes: from classical implants to tissue engineering materials.

After almost half a century of use in the health field, polyurethanes (PUs) remain one of the most popular group of biomaterials applied for medical devices. Their popularity has been sustained as a direct result of their segmented block copolymeric character, which endows them with a wide range of versatility in terms of tailoring their physical properties, blood and tissue compatibility, and more recently their biodegradation character. While they became recognized in the 1970s and 1980s as the blood contacting material of choice in a wide range of cardiovascular devices their application in long-term implants fell under scrutiny with the failure of pacemaker leads and breast implant coatings containing PUs in the late 1980s. During the next decade PUs became extensively researched for their relative sensitivity to biodegradation and the desire to further understand the biological mechanisms for in vivo biodegradation. The advent of molecular biology into mainstream biomedical engineering permitted the probing of molecular pathways leading to the biodegradation of these materials. Knowledge gained throughout the 1990s has not only yielded novel PUs that contribute to the enhancement of biostability for in vivo long-term applications, but has also been translated to form a new class of bioresorbable materials with all the versatility of PUs in terms of physical properties but now with a more integrative nature in terms of biocompatibility. The current review will briefly survey the literature, which initially identified the problem of PU degradation in vivo and the subsequent studies that have led to the field's further understanding of the biological processes mediating the breakdown. An overview of research emerging on PUs sought for use in combination (drug + polymer) products and tissue regeneration applications will then be presented.

Absorbable Implants↗

PubMed2005

The in vivo and in vitro degradation behavior of poly(trimethylene carbonate).

The in vivo and in vitro degradation behavior of poly(trimethylene carbonate) (PTMC) polymers with number average molecular weights of 69 x 10(3), 89 x 10(3), 291 x 10(3) and 457 x 10(3)g/mol (respectively abbreviated as PTMC(69), PTMC(89), PTMC(291) and PTMC(457)) was investigated in detail. PTMC rods (3mm in diameter and 4mm in length) implanted in the femur and tibia of rabbits degraded by surface erosion. The mass loss of high molecular weight PTMC(457) specimens was 60wt% in 8 wks, whereas the mass loss of the lower molecular weight PTMC(89) specimens in the same period was 3 times lower. PTMC discs of different molecular weights immersed in lipase solutions (lipase from Thermomyces lanuginosus) degraded by surface erosion as well. The mass and thickness of high molecular weight PTMC(291) discs decreased linearly in time with an erosion rate of 6.7 microm/d. The erosion rate of the lower molecular weight PTMC(69) specimens was only 1.4mum/d. It is suggested that the more hydrophilic surface of the PTMC(69) specimens prevents the enzyme from acquiring a (hyper)active conformation. When PTMC discs were immersed in media varying in pH from 1 to 13, the non-enzymatic hydrolysis was extremely slow for both the high and low molecular weight samples. It can be concluded that enzymatic degradation plays an important role in the surface erosion of PTMC in vivo.

Absorbable Implants↗

PubMed1998

Early peripheral nerve healing in collagen and silicone tube implants: myofibroblasts and the cellular response.

Injuries to peripheral nerves innervating a limb cause paralysis, and can necessitate amputation. The inability of the nerves to regenerate spontaneously and the limitations of autograft procedures led to the development of treatments involving insertion of the nerve ends into prosthetic tubular devices. Previous work showed that 'entubulation' of the nerve ends in a silicone tube containing a specific porous, resorbable collagen-GAG (CG) copolymer, serving as an analog of extracellular matrix, improved regeneration compared to an empty silicone tube. However, long-term treatment with silicone tubes produced constriction that caused partial degradation of the regenerated axons; for this and other reasons, implementation of a nondegradable tube may require a second surgical procedure for removal. In this study the silicone tube was replaced with porous and non-porous collagen tubes in order to produce fully degradable devices. CG-filled collagen tubes and controls (CG-filled silicone tubes and empty collagen and silicone tubes) were implanted in a 10-mm gap in the rat sciatic nerve, with three rats in each group. The regeneration was evaluated after six weeks using light microscope images of cross sections of the nerve that were digitized and analyzed. Histograms of the diameters of the axons were generated and compared. The cellular response to the implanted biomaterials was assessed histologically, and immunohistochemistry was performed using an antibody to alpha-smooth muscle actin in order to determine the presence of myofibroblasts (contractile cells). Axonal regrowth was comparable in porous collagen, non-porous collagen, and silicone tubes filled with a CG matrix. These results support the implementation of a degradable collagen tube in place of a silicone device. Confirming earlier work, regeneration through the silicone and collagen tubes was enhanced by the CG copolymer, compared to empty tubes. A notable finding was a continuous layer of myofibroblasts on the surfaces of all of the six silicone tube prostheses, but on the inner surface of only one of six collagen tubes (Fisher's exact tests; P < 0.01). This is the first report of contractile capsules around silicone tubes, and supports the use of degradable collagen tubes in peripheral nerve regeneration. Macrophages were found bordering both the silicone and collagen tubes, and in the case of the collagen tubes, appeared to be participating in the regulation of the tubes.

Absorbable Implants↗

PubMed2002

A histological study on experimental tooth movement into bone induced by recombinant human bone morphogenetic protein-2 in beagle dogs.

OBJECTIVE: The purpose of this preliminary study was to examine experimental tooth movement into newly generated bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2). METHOD: After extraction of the maxillary first premolars, bone defects were surgically created in eight adult beagle dogs using a 5-mm-diameter trepan bar. According to which material was grafted into the bone defects, animals were divided into the following four groups: (1) the rhBMP-2 group in which rhBMP-2 with a poly[ D,L-(lactide-co-glycolide)]/gelatin sponge complex was implanted; (2) the spongiosa group in which spongiosa from the tibia was grafted; (3) the nongrafted group in which no material was embedded; and (4) the control group in which only tooth extraction was performed. The osteoinductive activity of rhBMP-2 and tooth movement into the newly generated bone were examined by histological and morphometric comparisons of each group. RESULTS: Considerable new bone formation was observed at the grafted site both in the rhBMP-2 and in the spongiosa groups. The area of generated bone in the rhBMP-2 group was significantly greater than that in the spongiosa group. Newly generated bone, in both the rhBMP-2 and spongisosa groups, showed a similar histological response to orthodontic force as in normal alveolar bone in the control group. However, root resorption occurred on the pressure side in the rhBMP-2 group. CONCLUSION: These results indicated that rhBMP-2 might constitute an alternative material to autogeneous bone grafting for alveolar cleft defects. Further studies regarding tooth movement into generated bone induced by rhBMP-2 are suggested.

Absorbable Implants↗

PubMed2001

Scleral plug of biodegradable polymers containing ganciclovir for experimental cytomegalovirus retinitis.

PURPOSE: To evaluate the efficacy of a biodegradable scleral plug containing ganciclovir (GCV) in a rabbit model of human cytomegalovirus (HCMV) retinitis. METHODS: To develop a rabbit model for HCMV retinitis, HCMV solution was injected once into the vitreous cavity of pigmented rabbits. The treated animals were divided into three groups: group A received no treatment, group B was treated once with GCV solution, and group C was treated with a scleral plug containing GCV. Rabbits in group B received an intravitreal injection of GCV solution 1 week after HCMV inoculation. In group C, the scleral plug containing GCV was implanted in the vitreous of the rabbits 1 week after HCMV inoculation. Ophthalmoscopically, vitreoretinal findings in each group were graded from 0+ to 4+ every week for 4 weeks after HCMV injection. RESULTS: Eyes of group A rabbits showed whitish retinal exudates and vitreous opacities 3 days after HCMV inoculation. These materials increased gradually until 3 weeks after HCMV inoculation. Scores for vitreoretinal lesions were significantly lower in eyes of group B rabbits compared with those of group A at 1 week after GCV injection (P < 0.05). However, vitreoretinal inflammation in eyes of group B rabbits increased again thereafter, and no significant difference in inflammation between groups A and B was found 2 weeks after GCV injection. In eyes of group C, scores for vitreoretinal lesions were significantly lower compared with those in both group A and group B at 3 weeks after HCMV inoculation (P < 0.01). CONCLUSIONS: The results demonstrated that sustained release of GCV into the vitreous cavity with biodegradable scleral plugs was effective for the treatment of experimentally induced HCMV retinitis in rabbits.

Absorbable Implants↗