Development and Brain Delivery of Chitosan−PEG Nanoparticles Functionalized with the Monoclonal Antibody OX26

The inhibition of the caspase-3 enzyme is reported to increase neuronal cell survival following cerebral ischemia. The peptide Z-DEVD-FMK is a specific caspase inhibitor, which significantly reduces vulnerability to the neuronal cell death. However, this molecule is unable to cross the blood-brain barrier (BBB) and to diffuse into the brain tissue. Thus, the development of an effective delivery system is needed to provide sufficient drug concentration into the brain to prevent cell death. Using the avidin (SA)-biotin (BIO) technology, we describe here the design of chitosan (CS) nanospheres conjugated with poly(ethylene glycol) (PEG) bearing the OX26 monoclonal antibody whose affinity for the transferrin receptor (TfR) may trigger receptor-mediated transport across the BBB. These functionalized CS-PEG-BIO-SA/OX26 nanoparticles (NPs) were characterized for their particle size, zeta potential, drug loading capacity, and release properties. Fluorescently labeled CS-PEG-BIO-SA/OX26 nanoparticles were administered systemically to mice in order to evaluate their efficacy for brain translocation. The results showed that an important amount of nanoparticles were located in the brain, outside of the intravascular compartment. These findings, which were also confirmed by electron microscopic examination of the brain tissue indicate that this novel targeted nanoparticulate drug delivery system was able to translocate into the brain tissue after iv administration. Consequently, these novel nanoparticles are promising carriers for the transport of the anticaspase peptide Z-DEVD-FMK into the brain.

Squalenoyl adenosine nanoparticles provide neuroprotection after stroke and spinal cord injury

There is an urgent need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. However, many drugs with potential neuropharmacological activity, such as adenosine, are inefficient upon systemic administration because of their fast metabolization and rapid clearance from the bloodstream. Here, we show that conjugation of adenosine to the lipid squalene and the subsequent formation of nanoassemblies allows prolonged circulation of this nucleoside, providing neuroprotection in mouse stroke and rat spinal cord injury models. The animals receiving systemic administration of squalenoyl adenosine nanoassemblies showed a significant improvement of their neurologic deficit score in the case of cerebral ischaemia, and an early motor recovery of the hindlimbs in the case of spinal cord injury. Moreover, in vitro and in vivo studies demonstrated that the nanoassemblies were able to extend adenosine circulation and its interaction with the neurovascular unit. This Article shows, for the first time, that a hydrophilic and rapidly metabolized molecule such as adenosine may become pharmacologically efficient owing to a single conjugation with the lipid squalene.

Preparation and in vitro evaluation of chitosan nanoparticles containing a caspase inhibitor

The aim of this work was to develop a formulation for Z-DEVD-FMK, a peptide which is a caspase inhibitor and has been used in experimental animal studies for a decade. Peptide loaded chitosan nanoparticles were obtained by ionotropic gelation process and Z-DEVD-FMK was quantified by an HPLC method. The influence of the initial peptide concentration on the nanoparticle characteristics and release behavior was evaluated. The CS nanoparticles have a particle diameter (Z-average) ranging from approximately 313-412 nm and a positive zeta potential (20-28 mV). The formulation with the initial peptide concentration of 400 ng/ml provided the highest loading capacity (0.46%) and the highest extent of release (65% at 24 h) suggesting the possibility to achieve a therapeutic dose. According to the data obtained, this chitosan-based nanotechnology opens new and interesting perspectives for anticaspase activity.

Preparation and characterization of poly (D,L-lactide-co-glycolide) microspheres for controlled release of poly(L-lysine) complexed plasmid DNA

PURPOSE

To produce and characterize controlled release formulations of plasmid DNA (pDNA) loaded in poly (D,L-lactide-co-glycolide) (PLGA) microspheres both in free form and as a complex with poly (L-lysine).

METHODS

Poly (L-lysine) (PLL) was used to form pDNA/PLL complexes with complexation ratio of 1:0.125 and 1:0.333 w/w to enhance the stability of pDNA during microsphere preparation and protect pDNA from nuclease attack. pDNA structure, particle size, zeta potential, drug loading, in vitro release properties, and protection from DNase I were studied.

RESULTS

The microspheres were found to be spherical with average particle size of 3.1-3.5 microm. Drug loading of 0.6% was targeted. Incorporation efficiencies of 35.1% and 29.4-30.6% were obtained for pDNA and pDNA/PLL loaded microspheres respectively. Overall, pDNA release kinetics following the initial burst did not correlate with blank microsphere polymer degradation profile suggesting that pDNA release is convective diffusion controlled. The percentage of supercoiled pDNA in the pDNA and pDNA/PLL loaded microspheres was 16.6 % and 76.7-85.6% respectively. Unencapsulated pDNA and pDNA/PLL degraded completely within 30 minutes upon the addition of DNase I. Encapsulation of DNA/PLL in PLGA microspheres protected pDNA from enzymatic degradation.

CONCLUSIONS

The results show that using a novel process, pDNA can be stabilized and encapsulated in PLGA microspheres to protect pDNA from enzymatic degradation.

Influence of formulation parameters on the characteristics of poly(D, L-lactide-co-glycolide) microspheres containing poly(L-lysine) complexed plasmid DNA

This study describes the influence of polymer type, surfactant type/concentration, and target drug loading on the particle size, plasmid DNA (pDNA) structure, drug loading efficiency, in vitro release, and protection from DNase I degradation of poly(D, L-lactide-co-glycolide) (PLGA) microspheres containing poly(L-lysine) (PLL) complexed pDNA. PLGA microspheres containing pDNA-PLL were prepared using the water-in-oil-in-water (w-o-w) technique with poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) as surfactants in the external aqueous phase. A complex ratio of 1:0.33 (pDNA-PLL, w/w) enhanced the stability of pDNA during microsphere preparation. Higher pDNA-PLL loading efficiency (46.2%) and supercoiled structure (64.9%) of pDNA were obtained from hydrophobic PLGA (M(w) 31000) microspheres compared with hydrophilic PLGA or low-molecular-weight PLGA microspheres. The particle size decreased from 6.6 to 2.2 microm when the concentration of PVA was increased from 1 to 7%. At the same concentration of surfactant, PVA stabilized microspheres showed higher pDNA-PLL loading efficiency (46.2%) than PVP stabilized microspheres (24.1%). Encapsulated pDNA in PLGA microspheres was protected from enzymatic degradation and maintained in the supercoiled form. The pDNA-PLL microspheres showed in vitro release of 95.9 and 84.9% within 38 days from the low-molecular-weight PLGA and hydrophilic PLGA microspheres, respectively, compared to 54.2% release from the hydrophobic, higher-molecular-weight PLGA microspheres. The results suggest loading and release of pDNA-PLL complex can be influenced by surfactant concentration and polymer type.

Systemically administered brain-targeted nanoparticles transport peptides across the blood-brain barrier and provide neuroprotection

Although growth factors and anti-apoptotic peptides have been shown to be neuroprotective in stroke models, translation of these experimental findings to clinic is hampered by limited penetration of peptides to the brain. Here, we show that a large peptide like the basic fibroblast growth factor (bFGF) and a small peptide inhibitor of caspase-3 (z-DEVD-FMK) can effectively be transported to the brain after systemic administration by incorporating these peptides to brain-targeted nanoparticles (NPs). Chitosan NPs were loaded with peptides and then functionalized by conjugating with antibodies directed against the transferrin receptor-1 on brain endothelia to induce receptor-mediated transcytosis across the blood-brain barrier (BBB). Pre-ischemic systemic administration of bFGF- or z-DEVD-FMK-loaded NPs significantly decreased the infarct volume after 2-hour middle cerebral artery occlusion and 22-hour reperfusion in mice. Co-administration of bFGF- or z-DEVD-FMK-loaded NPs reduced the infarct volume further and provided a 3-hour therapeutic window. bFGF-loaded NPs were histologically detected in the brain parenchyma and also restored ischemia-induced Akt dephosphorylation. The neuroprotection was not observed when receptor-mediated transcytosis was inhibited with imatinib or when bFGF-loaded NPs were not conjugated with the targeting antibody, which enables them to cross the BBB. Nanoparticles targeted to brain are promising drug carriers to transport large as well as small BBB-impermeable therapeutics for neuroprotection against stroke.

Preparation and characterization of poly(D,L-lactide-co-glycolide) microspheres for controlled release of human growth hormone

The purpose of this research was to assess the physicochemical properties of a controlled release formulation of recombinant human growth hormone (rHGH) encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) composite microspheres. rHGH was loaded in poly(acryloyl hydroxyethyl) starch (acHES) microparticles, and then the protein-containing microparticles were encapsulated in the PLGA matrix by a solvent extraction/evaporation method. rHGH-loaded PLGA microspheres were also prepared using mannitol without the starch hydrogel microparticle microspheres for comparison. The detection of secondary structure changes in protein was investigated by using a Fourier Transfer Infrared (FTIR) technique. The composite microspheres were spherical in shape (44.6 +/- 2.47 microm), and the PLGA-mannitol microspheres were 39.7 +/- 2.50 microm. Drug-loading efficiency varied from 93.2% to 104%. The composite microspheres showed higher overall drug release than the PLGA/mannitol microspheres. FTIR analyses indicated good stability and structural integrity of HGH localized in the microspheres. The PLGA-acHES composite microsphere system could be useful for the controlled delivery of protein drugs.

Formulation and in vitro-in vivo evaluation of buccoadhesive morphine sulfate tablets

Buccoadhesive controlled-release systems for the delivery of morphine sulfate were prepared by compression of hydroxypropyl methylcellulose (HPMC) with carbomer (CP), which served as the bioactive adhesive compound. The release behavior of systems containing 30 mg of morphine sulfate and various amounts of the two polymers was found to be non-Fickian. The adhesion force was significantly affected by the mixing ratio of HPMC and CP in the tablet, and the weakest adhesion force was observed at a ratio of 1:1 (HPMC:CP). Interpolymer complex formation was confirmed between HPMC and CP in acidic medium by turbidity, viscosity, and FT-IR measurements. The amount absorbed (percentage of the drug loaded) of the controlled-release buccoadhesive tablets in six healthy volunteers and was 30 +/- 5%.

Stability of Antimicrobial Decapeptide (KSL) and Its Analogues for Delivery in the Oral Cavity

PURPOSE

To investigate the stability of KSL, an antimicrobial decapeptide, and its analogues, in human saliva and simulated gastric fluid for delivery in the oral cavity.

MATERIALS AND METHODS

The degradation products of KSL in human saliva and simulated gastric fluid were separated by reversed-phase HPLC and their structures were identified by electrospray ionization-mass spectrometry. Analogues of KSL were synthesized by solid-phase synthesis procedure. Their enzymatic stabilities and antimicrobial activities were studied.

RESULTS

KSL was degraded by the peptide bond cleavages at Lys(6)-Val(7) in the human saliva and Phe(5)-Lys(6) in simulated gastric fluids. Three analogues of KSL were synthesized; the Lys(6) residue was either methylated (KSL-M), or replaced with Trp (KSL-W), or the d-form of Lys (KSL-D). The KSL analogues were much more stable than the native KSL, with the rank order of stability being KSL-D > KSL-W > KSL-M > KSL in human saliva. However, in simulated gastric fluid, while KSL-D was still stable, KSL-W was significantly degraded. In addition, KSL-D significantly lost the antimicrobial activity, whereas KSL-W completely preserved the activity against several oral bacteria. In a chewing gum formulation, KSL-W showed a more sustained release profile as compared with the native KSL.

CONCLUSION

This study suggests that KSL-W could be used as an antiplaque agent in a chewing gum formulation.

Development of a peptide-containing chewing gum as a sustained release antiplaque antimicrobial delivery system

The objective of this study was to characterize the stability of KSL-W, an antimicrobial decapeptide shown to inhibit the growth of oral bacterial strains associated with caries development and plaque formation, and its potential as an antiplaque agent in a chewing gum formulation. KSL-W formulations with or without the commercial antibacterial agent cetylpyridinium chloride (CPC) were prepared. The release of KSL-W from the gums was assessed in vitro using a chewing gum apparatus and in vivo by a chew-out method. A reverse-phase high-performance liquid chromatography method was developed for assaying KSL-W. Raw material stability and temperature and pH effects on the stability of KSL-W solutions and interactions of KSL-W with tooth-like material, hydroxyapatite discs, were investigated. KSL-W was most stable in acidic aqueous solutions and underwent rapid hydrolysis in base. It was stable to enzymatic degradation in human saliva for 1 hour but was degraded by pancreatic serine proteases. KSL-W readily adsorbed to hydroxyapatite, suggesting that it will also adsorb to the teeth when delivered to the oral cavity. The inclusion of CPC caused a large increase in the rate and extent of KSL-W released from the gums. The gum formulations displayed promising in vitro/in vivo release profiles, wherein as much as 90% of the KSL-W was released in a sustained manner within 30 minutes in vivo. These results suggest that KSL-W possesses the stability, adsorption, and release characteristics necessary for local delivery to the oral cavity in a chewing gum formulation, thereby serving as a novel antiplaque agent.

Chewing gum of antimicrobial decapeptide (KSL) as a sustained antiplaque agent: preformulation study

The purpose of this study was to investigate the potential of KSL, an antimicrobial decapeptide, which has been shown to inhibit the growth of oral bacterial strains associated with caries development and plaque formation, to act as an antiplaque agent in a chewing gum formulation. A reversed-phase high-performance liquid chromatography method was developed for KSL and found to be stability-indicating. KSL was stable in acetate buffer at pH 4 and artificial saliva. On the affinity of KSL to tooth-like materials, the KSL showed favorable interaction with hydroxyapatite discs pretreated with human saliva. A chewing gum formulation of KSL was prepared based on conventional procedures and the release of KSL from the gum was studied in vitro using the chewing apparatus and in vivo by a chew-out method. The gum formulations showed promising in vitro/in vivo release profiles, in which 70-80% KSL was released in a sustained manner over 20 min of chewing time. This study suggests that KSL in a gum formulation is suitable for the delivery in the oral cavity, thereby serving as a novel antiplaque agent.

Treatment of malignant gliomas with mitoxantrone-loaded poly (lactide-co-glycolide) microspheres

OBJECTIVE

Mitoxantrone (MTZ) has potent in vitro activity against malignant glioma cell lines, but it cannot be used effectively as a systemic agent for the treatment of brain tumors because of its poor central nervous system penetration. However, MTZ-loaded poly(lactide-co-glycolide) (PLGA) microspheres may be injected into the peritumoral area and into tumor tissue to provide effective and sustained local drug concentrations without causing systemic side effects.

METHODS

Fisher rats were randomized into three groups. The first group (n = 9) was concomitantly implanted with rat glioma (RG2) cells and blank PLGA microspheres. The second group (n = 6) was implanted with RG2 cells and MTZ-loaded PLGA microspheres. The third group (n = 9) was implanted with RG2 cells, and MTZ-loaded PLGA microspheres were injected into the same area after 7 days. Animals were sacrificed on Day 15 or 35. Tumor volumes were measured after hematoxylin and eosin staining. Distribution kinetics of MTZ in the brain was determined by high-performance liquid chromatography in nine rats injected with MTZ-loaded microspheres.

RESULTS

The tumor volumes were 76 +/- 11 and 107 +/- 11 mm (mean +/- standard error) on Days 15 (n = 6) and 35 (n = 3), respectively, in the control group. In rats treated with MTZ-loaded microspheres on Day 7, tumor volumes were significantly reduced to 17 +/- 4 and 23 +/- 2 mm on Days 15 (n = 6) and 35 (n = 3), respectively. No tumor formation was observed when glioma cells and MTZ-loaded PLGA microspheres were implanted concomitantly (n = 6). No systemic side effects or parenchymal inflammatory infiltration were observed in either group of rats. Brain MTZ concentration was highest at the injection site and declined with time and distance from the injection site and with time.

CONCLUSION

These data demonstrate that MTZ-loaded PLGA microspheres can deliver therapeutic concentrations of drug to the tumor and prevent glioma growth without causing side effects. This treatment method may increase the efficiency of antineoplastic therapy and positively impact survival.

Stability of poly(L-lysine)-complexed plasmid DNA during mechanical stress and DNase I treatment

The aim of this study was to investigate the formation and stability of complexes between plasmid DNA (pDNA) and poly(L-lysine) (PLL). Formation of pDNA/PLL complexes with various ratios was determined by a fluorescence spectrophotometric method using fluorescamine. The effects of sonication, vortexing, and exposure to DNase I on the stability of free pDNA and pDNA/PLL complexes are discussed. A linear correlation between PLL added and PLL bound was obtained with overall reaction efficiency of 84.2-92.6%. Sonication degraded both free and PLL-complexed pDNA within 15 sec of vortexing. However, vortexing did not alter the stability of free and complexed pDNA. Dramatic increase in the protection of pDNA in pDNA/PLL complexes was observed in the DNase I digestion experiment; 68.1-89.0% of total pDNA in the pDNA/PLL complexes was protected from DNase I digestion compared to only 19.2% of total pDNA that remained undegraded after DNase I treatment of free pDNA. An increase in the PLL/pDNA ratio led to an increase in the protection of supercoiled pDNA; 15.5-38.2% of supercoiled pDNA pin PLL/pDNA complexes was protected after DNase I treatment. The results show that complexation of pDNA with PLL can stabilize the supercoiled structure of pDNA for the development of biodegradable microspheres as a delivery system for pDNA. Stability of pDNA/PLL complex can be monitored by PicoGreen dye and fluorescence densitometric assay methods.

Combination of Paclitaxel and R-flurbiprofen loaded PLGA nanoparticles suppresses glioblastoma growth on systemic administration

Malignant gliomas are highly lethal. Delivering chemotherapeutic drugs to the brain in sufficient concentration is the major limitation in their treatment due to the blood-brain barrier (BBB). Drug delivery systems may overcome this limitation and can improve the transportation through the BBB. Paclitaxel is an antimicrotubule agent with effective anticancer activity but limited BBB permeability. R-Flurbiprofen is a nonsteroidal antienflammatory drug and has potential anticancer activity. Accordingly, we designed an approach combining R-flurbiprofen and paclitaxel and positively-charged chitosan-modified poly-lactide-co-glycolic acid (PLGA) nanoparticles (NPs) and to transport them to glioma tissue. NPs were characterized and, cytotoxicity and cellular uptake studies were carried out in vitro. The in vivo efficacy of the combination and formulations were evaluated using a rat RG2 glioma tumor model. Polyethylene glycol (PEG) modified and chitosan-coated PLGA NPs demonstrated efficient cytotoxic activity and were internalized by the tumor cells in RG2 cell culture. In vivo studies showed that the chitosan-coated and PEGylated NPs loaded with paclitaxel and R-flurbiprofen exhibited significantly higher therapeutic activity against glioma. In conclusion, PLGA NPs can efficiently carry their payloads to glioma tissue and the combined use of anticancer and anti-inflammatory drugs may exert additional anti-tumor activity.

Preparation and characterization of PLGA nanospheres for the targeted delivery of NR2B-specific antisense oligonucleotides to the NMDA receptors in the brain

Treatment of central nervous system (CNS) diseases with potentially useful pharmaceuticals is prevented by the blood-brain barrier (BBB). The BBB is a unique protective barrier in the body. It is formed by epithelial-like tight junctions, which are expressed by the brain capillary endothelial cells. Although most molecules are potentially active in the CNS, they cannot readily enter the brain because of their properties. Antisense oligonucleotides (ODNs) have a great potential as neuropharmaceuticals; however, the large size and polar nature of nucleic acid drugs prevent these molecules from bypassing the BBB and readily entering the CNS following systemic administration. One approach to improve both the pharmacokinetics and the pharmacodynamics of ODNs involves the use of sustained-release polymer formulations, such as poly(lactide-co-glycolide) (PLGA) nanoparticulate systems. In this study, nanospheres were prepared by the emulsification diffusion technique and characterized in terms of particle size, surface morphology, encapsulation efficiency, in vitro release profiles and ODN stability. The nanospheres produced were spherical with homogenous size distribution. Nanospheres were prepared with different encapsulation efficiency. Release profiles of formulations were also evaluated. The results show that formulations with different ODN content exhibited different release profiles. Moreover, the chemical integrity of ODN during the processes was conserved. These results demonstrate that a stable ODN formulation could be prepared utilizing PLGA nanospheres as a potential delivery system for the treatment of CNS diseases.

In vitro studies on enhancing effect of sodium glycocholate on transbuccal permeation of morphine hydrochloride

During the perioperative period, gastric emptying rate and first-pass metabolism limit the use of peroral morphine. Buccal mucosa appears to be a potential site for delivery of morphine as it provides direct entry into the system circulation thereby avoiding the hepatic first-pass effect. However, the low permeability of the buccal epithelium results in a low flux of the drug. The use of a penetration enhancer is required to improve the bioavailability of the drug via buccal route. In this study, the enhancing effect of sodium glycocholate (GC) used at 10 mM and 100 mM concentrations on permeation of morphine hydrochloride (MPH) across the porcine buccal mucosa was studied in vitro. Furthermore, in conjunction with its permeation, accumulation of GC in the tissue with time was also studied in order to elucidate the relationship between GC and enhanced mucosal permeation of the drug. Franz diffusion cells were used in the experiments. Permeation of MPH was increased in the presence of 100 mM GC with an enhancement factor of 9.3 whereas no enhancement was obtained with 10 mM GC. The calculated permeability coefficient for MPH in the presence of 100 mM GC was 2.35 x 10(-5) cm/s. Accumulation of GC at 100 mM in the tissue appears to be more significant at 100 mM concentration which correlated well with the increased permeation of the drug. GC was diffused through the buccal epithelium significantly at 100 mM concentration. Interaction of GC with the tissue appears to be more significant at 100 mM concentration compared to 10 mM concentration, thus resulting in a significant enhancing effect.

Preparation and Characterization of Biocompatible Chitosan Nanoparticles for Targeted Brain Delivery of Peptides

Here, we describe a nanocarrier system that can transfer chitosan nanoparticles loaded with either small peptides such as the caspase inhibitor Z-DEVD-FMK or a large peptide like basic fibroblast growth factor across the blood-brain barrier. The nanoparticles are selectively directed to the brain and are not measurably taken up by the liver and spleen. Intravital fluorescent microscopy provides an opportunity to study the penetration kinetics of nanoparticles loaded with fluorescent agents such as Nile red. Nanoparticles functionalized with anti-transferrin antibody and loaded with peptides efficiently provided neuroprotection when systemically administered either as a formulation bearing a single peptide or a mixture of them. Failure of brain permeation of the nanoparticles after inhibition of vesicular transcytosis by imatinib as well as when nanoparticles were not functionalized with anti-transferrin antibody indicates that this nanomedicine formulation is rapidly transported across the blood-brain barrier by receptor-mediated transcytosis.

Preparation and characterization of salmon calcitonin-biotin conjugates

This study was performed to prepare and characterize the biotinylated Salmon calcitonin (sCT) for oral delivery and evaluate the hypocalcemic effect of biotinylated-sCTs in rats. Biotinylated sCTs was characterized by using high performance liquid chromatography (HPLC) and MALDITOF-MS. The effect of biotinylation on permeability across Caco-2 cell monolayers was examined. Their hypocalcemic effect was determined in rats. Mono- and di-bio-sCTs were separated by reverse phase HPLC. The molecular weights of mono-bio-sCT and di-bio-sCT were determined to be 3,660.5 and 3,900.2 Da, respectively. The permeability of biotinylated-sCTs across Caco-2 cell monolayers was observed with a significant enhancement compared with sCT. Intrajejunal (ij) administration of mono-bio-sCT and di-bio-sCT resulted in sustained reduction in serum calcium levels, with a maximum reduction (% max(d)) of 21.6% and 30% after 4 h and 6 h of application, respectively. The biotin conjugation of sCT may be a promising strategy for increasing the oral bioavailability of sCT and achieving sustained calcium-lowering effects.

Histologic and histomorphometric assessment of eggshell-derived bone graft substitutes on bone healing in rats

OBJECTIVE

The objective of this study was to histologically and histomorphometrically evaluate the efficacy of the new formulations of eggshell-derived calcium carbonate in rats.

STUDY DESIGN

The study was conducted on 30 adult male rats. Four standardized and circular intrabony defects were created in the both maxilla and mandibula of each animal. Three different graft materials were prepared as follows: 1) Material A: Eggshell-derived calcium carbonate combined with carrageenan gel, 2) Material B: Eggshell-derived calcium carbonate combined with xanthan gum gel, and 3) Material C: Eggshell-derived calcium carbonate powder. The right mandibular defect sites were grafted with Material A in all animals, and defects on the left were grafted with Material B. Defects on the right side of maxilla were received Material C in all animals, and all left maxillary defects were remained untreated as controls. The animals were sacrificed either postoperatively on the 15th day, postoperatively on the 30th day or postoperatively on the 45th day. Histomorphometric measurements were made of the areas of newly formed bone, necrotic bone, fibrous tissue and residual graft material.

RESULTS

Material A exhibited the highest level of osteoid formation followed by Material B and Material C on the 45th day. In terms of osteoid formation, statistically significant differences were observed between graft materials and controls at 45th day compared to 15th and 30th day (p<0.05).

CONCLUSIONS

Eggshell-derived graft substitutes in both gel and powder forms are biocompatible materials which may have the potential to enhance the new bone formation. Key words:Bone graft material, bone defects, eggshell, histopathological evaluation, rat.