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At least 199 records · Page 11Linked to original sources
PubMed2004

Measuring the heterogeneity of protein loading in PLG microspheres using flow cytometry.

Poly (DL-lactide co-glycolide) (PLG) microspheres with mean sizes up to 1 microm containing Fluorescein Isothiocyanate labelled Bovine Serum Albumin (FITC-BSA) were prepared by the water-in oil-in water (w/o/w) emulsion solvent evaporation technique. Protein loading and loading efficiency determined by the BCA total protein assay increased with microsphere size as measured by laser diffractometry. Protein loaded microspheres were analysed using flow cytometry (FC) to provide fast and reproducible measurements of the size and protein loading of individual microspheres within a sample thereby quantifying in detail the batch heterogeneity. The FC analysis demonstrated that as the size of individual microspheres within a batch increased, so the protein loading tended to increase. For example, the protein loading of microspheres increased from 2.7 to 8.9 wt.% as the size of microspheres increased from 0.42 to 1.45 microm, respectively. Measurements taken during a subsequent protein release experiment indicated that smaller microspheres within a sample released their protein more quickly than larger sizes. Flow cytometry has been shown to provide detailed information, at the level of individual microspheres, about the heterogeneity in size and protein loading of a microsphere sample and could thus lead to improvement of the release characteristics of microsphere-based delivery systems for biopharmaceuticals.

Animals↗
PubMed2005

Preparation of uniform sized chitosan microspheres by membrane emulsification technique and application as a carrier of protein drug.

The control of size and size distribution of microspheres is necessary for obtaining repeatable controlled release behavior. The chitosan microspheres were prepared by a membrane emulsification technique in this study. Chitosan was dissolved in 1 wt.% aqueous acetic acid containing 0.9 wt.% sodium chloride, which was used as a water phase. A mixture of liquid paraffin and petroleum ether 7:5 (v/v) containing PO-500 emulsifier was used as an oil phase. The water phase was permeated through the uniform pores of a porous glass membrane into the oil phase by the pressure of nitrogen gas to form W/O emulsion. Then GST (Glutaraldehyde Saturated Toluene) as crosslinking agent was slowly dropped into the W/O emulsion to solidify the chitosan droplets. The preparation condition for obtaining uniform-sized microspheres was optimized. The microspheres with different size were prepared by using the membranes with different pore size, and there was a linear relationship between the diameter of microspheres and pore size of the membranes when the microspheres were in the range of micron size. The smallest chitosan microspheres obtained was 0.4 mum in diameter. This is the first report for preparing the uniform-sized chitosan microspheres by membrane emulsification technique. Uniform chitosan microspheres were further used as a carrier of protein drug. Bovine serum albumin (BSA) as a model drug was loaded in the microspheres and released in vitro. The effects of pH value, diameter and crosslinking degree of microspheres, and BSA concentration on loading efficiency and release behavior were discussed.

Adsorption↗
PubMed2006

Silk microspheres for encapsulation and controlled release.

A method was developed to prepare silk fibroin microspheres using lipid vesicles as templates to efficiently load protein drugs in active form for controlled release. The lipid was subsequently removed by methanol or sodium chloride treatments, resulting in silk microspheres consisting of beta-sheet structure and about 2 mum in diameter. NaCl treated microspheres had smoother surfaces compared to the methanol treatments based on SEM analysis, and both types of microspheres had a mixture of multilamellar and unilamellar structures. A model protein drug, horseradish peroxidase, was encapsulated in the microspheres. Freeze-thaw cycles during preparation led to higher loading of the peroxidase due to improved mixing between the silk and drug, while without this process the drug and silk remained in separate layers or domains in microspheres. This partitioning was determined with fluorescein-labeled silk and rhodamine-labeled dextran. Small molecules such as the enzyme substrate 3,3',5,5'-tetramethylbenzidine, Mw=240 Da, and its oxidized product freely diffused through the MeOH- and NaCl-processed silk microspheres so that enzyme loading and activity could be determined. Enzyme activity was retained during processing and in the final microspheres. The enzyme release profile depended on the NaCl-process used in microsphere preparation. The physically cross-linked beta-sheet structure of silk fibroin and the residual lipids in the microspheres played important roles in controlling enzyme release profiles. The silk microspheres have the potential for diverse applications where controlled protein release from biocompatible, mechanically tough, and slowly biodegradable carriers is desirable.

Delayed-Action Preparations↗
PubMed2002

Effect of tricaprin on the physical characteristics and in vitro release of etoposide from PLGA microspheres.

The purpose of this article is to examine the effects of tricaprin on the physical characteristics and in vitro release of etoposide from poly (lactic-co-glycolic acid) microspheres. The microspheres were synthesized through the use of a single-emulsion solvent-extraction procedure. Samples from each batch of microspheres were then analyzed for size distribution, drug loading efficiency, surface characteristics, in vitro release, and in vitro degradation of microspheres. Microsphere batches were synthesized using three different etoposide concentrations (15%, 10%, and 5% w/w) with tricaprin concentrations of 25% and 50%. The incorporation of 50% tricaprin significantly increased (p<0.05) the size of the microspheres for all three etoposide concentrations in comparison to microspheres prepared without tricaprin (control). The percentage of tricaprin used did not significantly affect the drug loading efficiency of the microspheres. The addition of tricaprin was shown to significantly increase (p<0.05) the in vitro release of etoposide from the microspheres prepared with all three concentrations of etoposide and the two different tricaprin percentages. Examination of the surface characteristics of the tricaprin loaded microspheres showed a dimpled surface with what appeared to be pockets of tricaprin dispersed throughout. In the in vitro degradation study, the tricaprin microspheres grew very porous as the degradation time increased, but they still retained a recognizable structure even after 30 days of degradation.

Biocompatible Materials↗
PubMed2000

Controlled release of macromolecules from PLA microspheres: using porous structure topology.

Release of hydrophilic macromolecules (FITC-dextran, M(w)=71 and 2000 kDa) from porous poly (D,L-lactic acid), PLA, microspheres was studied by applying percolation theory. Microspheres were prepared by the double emulsion method using high molecular weight PLA. The microspheres showed a percolation threshold, rho(C), at porosity 0. 34. From this parameter, the effective diffusion coefficients, D(eff), and the accessible porosity (total releasable active ingredient), rho(A), of the microspheres were calculated using the Bethe lattice model with coordination number 4. Decreasing porosity of the microspheres decreased the release rate of the active ingredients and a long-term release was observed for the microspheres with porosity close to rho(C). The calculated rho(A) agreed with the experimental data and also the calculated D(eff) for the microspheres with larger porosity (>0.4) was a good estimation to predict the experimentally determined release profiles by applying the continuum structure model (CSM). For microspheres with porosity larger than 0.4 which contained FITC-dextran M(w)=71 kDa, a lag time was observed, which was attributed to delayed saturation of the microspheres with release medium. For microspheres with porosity close to rho(C), the limited number of exit holes on the exterior surface changed the mechanism of release and controlled the release rate rather than the tortuosity of the porous structure of the microspheres.

Algorithms↗
PubMed2002

Precise control of PLG microsphere size provides enhanced control of drug release rate.

An important limitation in the development of biodegradable polymer microspheres for controlled-release drug delivery applications has been the difficulty of specifically designing systems exhibiting precisely controlled release rates. Because microparticle size is a primary determinant of drug release, we developed a methodology for controlling release kinetics employing monodisperse poly(D,L-lactide-co-glycolide) (PLG) microspheres. We fabricated 20-, 40- and 65-microm diameter rhodamine-containing microspheres and 10-, 50- and 100-microm diameter piroxicam-containing microspheres at various loadings from 1 to 20%. In vitro release kinetics were determined for each preparation. Drug release depended strongly on microsphere diameter with 10- and 20-microm particles exhibiting concave-downward release profiles while larger particles resulted in sigmoidal release profiles. Overall, the rate of release decreased and the duration increased with increasing microsphere size. Release kinetics from mixtures of uniform microspheres corresponded to mass-weighted averages of the individual microsphere release kinetics. Appropriate mixtures of uniform microspheres were identified that provided constant (zero-order) release of rhodamine and piroxicam for 8 and 14 days, respectively. Mixing of uniform microspheres, as well as control of microsphere size distribution, may provide an improved methodology to tailor small-molecule drug-release kinetics from simple, biodegradable-polymer microparticles.

Biocompatible Materials↗
PubMed2003

Poly(lactide-co-glycolide) microspheres containing bupivacaine: comparison between gamma and beta irradiation effects.

The beta- and gamma-irradiation effects on stability of microspheres made of poly(lactide-co-glycolide) 50:50 copolymer (PLGA) containing bupivacaine (BU) were studied. Microspheres containing 10, 25, and 40% w/w, respectively, of BU were prepared by spray drying and irradiated in air with beta- and gamma-irradiation at a dose of 25 kGy. Morphology (atomic force microscopy, particle-size analysis), physico-chemical characteristics (DSC and FT-IR spectroscopy), drug content and in vitro dissolution profile of microspheres were all determined; the stability of irradiated microspheres was evaluated over a 9-month period. The decrease of BU content in gamma-irradiated microspheres was almost always constant independent of the amount of BU per sample, therefore it was in inverse proportion to drug loading (range between 5 and 15%). BU release rate increased immediately after irradiation and increased slightly until 90 days of storage. As far as beta-irradiated microspheres are concerned, BU content decreased in a significant way (approximately 3%) only in microspheres containing 10% w/w of BU. Immediately after irradiation, drug release rate in beta-irradiated microspheres increased less than in the corresponding gamma-irradiated microspheres, and it did not change further over the following storage period. BU-loaded microspheres have been shown to be more stable against beta- than gamma-irradiation. AFM revealed that the surface roughness of the irradiated microspheres increases depending on irradiation. As such, if a parameter is quantifiable, it is proposed as a marker of degradation due to ionizing radiation.

Anesthetics, Local↗
PubMed1999

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.

DNA Adducts↗
PubMed2000

Pharmacokinetics of prolonged-release CPT-11-loaded microspheres in rats.

CPT-11-containing microspheres composed of poly-D,L-lactic acid or poly (D,L-lactic acid-co-glycolic acid) copolymers were prepared by an oil-in-water evaporation method. The size and shape of the microspheres were examined, and the drug release rates were analyzed from the in vitro release profiles. CPT-11 aqueous solution was intravenously or intraperitoneally injected at 10 mg/kg, and microspheres were intraperitoneally administered at 50 mg eq CPT-11/kg in rats. The microspheres had an average diameter of around 10 microm and their shape was spherical. All the microspheres contained CPT-11 in a lactone form, and their drug contents and release profiles were basically similar to those of previous microspheres. After i.v. injection of CPT-11 solution, the CPT-11 plasma concentration decreased quickly, SN-38 decreased slowly at a much lower level, and SN-38 glucuronide (SN-38G) declined very slowly at a higher level than SN-38. The plasma concentration of CPT-11 reached a maximum at 30 min after i.p. administration of CPT-11 solution. The area under the plasma concentration-time curve (AUC) of CPT-11 after i.p. administration was somewhat lower compared with that after i.v. administration, but the plasma concentration-time profiles of SN-38 and SN-38G were nearly identical between i.v. and i.p. administration. An i.p. administration of the microspheres resulted in gradually increasing or almost constant CPT-11 levels. The levels of SN-38 were also stable during the observation period (4 days) except for the slowest releasing microsphere in which SN-38 was not detected after 24 h following administration. Intraperitoneal administration of any of the microspheres resulted in stable and similar levels of SN-38G after 24 h following administration. When judging from apparent simple pharmacokinetic analysis, an inconsistency was found between the in vitro drug release and the plasma level to a fair extent, but overall the in vivo drug release rate from microspheres was considered parallel to the in vitro one. The microspheres showing a faster release of CPT-11 exhibited higher plasma levels of CPT-11 and SN-38, explaining the previous results that efficacy was better when the in vitro release rate was higher. That the SN-38 level could be attained to a certain extent even at the range of modest or low plasma concentration of CPT-11 in each administration may be related to the non-linear metabolic conversion from CPT-11 to SN-38.

Animals↗
PubMed1988

Chromatographic studies of mitomycin C degradation in albumin microspheres.

Serum albumins and polylactic acid (PLA) have been used as bioerodable polymers in the preparation of drug-containing microspheres for parenteral drug delivery. The albumin microsphere may be prepared via either chemical cross-linking or heat denaturation of the protein. Heat-denatured albumin microspheres containing mitomycin C (MMC) have been used in pre-clinical and clinical investigations. Due to the high reactivity of MMC as a bifunctional alkylating agent, a study on the stability of MMC in the albumin and PLA microspheres has been carried out using a high-performance liquid chromatographic (HPLC) method. Human serum albumin (HSA) microspheres were prepared using an emulsion method via either heat denaturation at 120 or 170 degrees C or the use of 0.5 M biacetyl as a cross-linking agent. The PLA microspheres were prepared by an emulsion method at 55 degrees C. HPLC analysis of the HSA microspheres showed that about 37% of MMC was converted to 2,7-diaminomitosene derivatives in microspheres prepared by heat denaturation at 120 degrees C. The degradation increased to 82% when the microspheres were prepared with a denaturation temperature of 170 degrees C. The use of biacetyl as a cross-linking agent in the preparation of HSA microspheres resulted in a complete degradation of the incorporated MMC. Biacetyl was found to interact with MMC leading to the formation of 7-aminomitosene derivatives. In contrast to the albumin system, MMC may be incorporated into PLA microspheres without degradation.

Albumins↗
PubMed2003

In vitro and in vivo evaluation of mucoadhesive microspheres consisting of dextran derivatives and cellulose acetate butyrate.

The objective of this study was to evaluate mucoadhesive properties and gastrointestinal transit of microspheres made of oppositely charged dextran derivatives and cellulose acetate butyrate (CAB). The microspheres were prepared by emulsion solvent evaporation method. A reference microsphere was made of lactose instead of dextran derivatives. Microspheres with a diameter of 425-710 microm were examined for in vitro mucoadhesion by the everted sac method. The results indicated that the percentage of adherence to the rat small intestine was affected by the amount of dextran derivatives in the microspheres. After 1.5h, the adhering percent of the reference microspheres and the microspheres containing 50% of dextran derivatives were 34 and 74%, respectively. Then gastrointestinal transit after oral administration to rats was evaluated by counting the microspheres remaining in the stomach and small intestine. The microspheres containing 40% of dextran derivatives adhered to the stomach rather than the small intestine. Mathematical analysis revealed that the time required for 50% of microspheres to leave the stomach was 1.42h, three times longer than the reference. These findings suggest that the microsphere is a promising device as a multiple-unit mucoadhesive system.

Adhesiveness↗
PubMed1999

A heterogeneously structured composite based on poly(lactic-co-glycolic acid) microspheres and poly(vinyl alcohol) hydrogel nanoparticles for long-term protein drug delivery.

PURPOSE: To prepare a heterogeneously structured composite based on poly (lactic-co-glycolic acid) (PLGA) microspheres and poly(vinyl alcohol) (PVA) hydrogel nanoparticles for long-term protein drug delivery. METHODS: A heterogeneously structured composite in the form of PLGA microspheres containing PVA nanoparticles was prepared and named as PLGA-PVA composite microspheres. A model protein drug, bovine serum albumin (BSA), was encapsulated in the PVA nanoparticles first. The BSA-containing PVA nanoparticles was then loaded in the PLGA microspheres by using a phase separation method. The protein-containing PLGA-PVA composite microspheres were characterized with regard to morphology, size and size distribution, BSA loading efficiency, in vitro BSA release, and BSA stability. RESULTS: The protein-containing PLGA-PVA composite microspheres possessed spherical shape and nonporous surface. The PLGA-PVA composite microspheres had normal or Gaussian size distribution. The particle size ranged from 71.5 microm to 282.7 microm. The average diameter of the composite microspheres was 180 microm. The PLGA-PVA composite microspheres could release the protein (BSA) for two months. The protein stability study showed that BSA was protected during the composite microsphere preparation and stabilized inside the PLGA-PVA composite microspheres. CONCLUSIONS: The protein-containing PLGA-PVA composite may be suitable for long-term protein drug delivery.

Biocompatible Materials↗
PubMed1993

Determinants of release rate of tetanus vaccine from polyester microspheres.

Controlled-release formulations based on poly(lactic) (PLA) and poly(lactic/glycolic) acid (PLGA) microspheres containing tetanus vaccine were designed. The polymers forming the microspheres were L-PLA of different molecular weights and DL-PLGA, 50:50. These microspheres were prepared by two solvent elimination procedures, both using a double emulsion, and were characterized for size, morphology, and toxoid release kinetics. The influence of formulation variables such as polymer type, vaccine composition, and vaccine/polymer ratio was also investigated. Both techniques yielded microspheres with similar size, morphology, and release properties. Microsphere size was dependent on the type of polymer and the presence of the surfactant L-alpha-phosphatidylcholine, which led to a reduction in microsphere size. On the other hand, the release kinetics of encapsulated protein were affected by the polymer properties (ratio lactic/glycolic acid and molecular weight) as well as by the vaccine composition, vaccine loading, and microsphere size. Moreover, for some formulations, a decrease in microsphere size occurred simultaneously, with an increase in porosity leading to an augmentation of release rate. The changes in the PLA molecular weight during in vitro release studies indicated that release profiles of tetanus toxoid from these microspheres were only marginally influenced by polymer degradation. A significant fraction of protein (between 15 and 35%) was initially released by diffusion through water-filled channels. In contrast, the decrease in the PLGA molecular weight over the first 10 days of incubation suggested that erosion of the polymer matrix substantially affects protein release from these microspheres. Among all formulations developed, two differing in microsphere size, polymer hydrophobicity, and release profile were selected for in vivo administration to mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Dissolution, stability, and morphological properties of conventional and multiphase poly(DL-lactic-co-glycolic acid) microspheres containing water-soluble compounds.

Multiphase microspheres of poly(DL-lactic-co-glycolic acid) (PLGA) containing water-soluble compounds were prepared by a multiple-emulsion solvent evaporation technique. These compounds were dissolved in the aqueous phase of a W/O emulsion with soybean oil as the oil phase. This emulsion was dispersed throughout the matrix of the microsphere. The morphological properties of the multiphase microspheres during in vitro dissolution studies were compared to those of conventional microspheres prepared from the same polymer. Drug release from the multiphase microspheres was characterized by an initial uniform release for the first 20 days followed by a more rapid phase of drug release. Chlorpheniramine maleate (CPM) and brilliant blue (BB) were the soluble model compounds investigated. The release rates of these agents from the multiphase microspheres were independent of the drug content in the microspheres. The release profiles from the conventional microspheres showed a lag time of 10 and 16 days for the CPM and BB, respectively. The dissolution rate of the model soluble compounds from the conventional microspheres increased as the loading in the microspheres increased. No differences in the degradation rate of the PLGA from the multiphase and the conventional microspheres were seen during the dissolution studies.

Acetonitriles↗
PubMed1993

Polyanhydride microspheres that display near-constant release of water-soluble model drug compounds.

A new method to prepare polyanhydride microspheres capable of near-constant sustained release of low molecular weight, water-soluble molecules is presented. The polyanhydrides used were poly(fatty acid dimer) (PFAD), poly(sebacic acid) (PSA), and their copolymers [P(FAD-SA)]. Acid orange 63 (AO), acid red 8 (AR), and p-nitroaniline, were used as model release molecules. P(FAD-SA) microspheres containing the molecules with or without gelatin were prepared by a modified solvent evaporation method using a double emulsion. The microspheres were spherical with diameters of 50-125 microns and encapsulated more than 85% of the molecule, irrespective of the compound used. Near-zero-order degradation kinetics were observed for 5 days as judged by sebacic acid (SA) release. Microsphere degradation was pH sensitive, being enhanced at high pH, and became more stable in acidic conditions, irrespective of the incorporation of gelatin in the matrix. For the gelatin-free microspheres, a close correlation of SA release and AO release was observed (2% loading), suggesting a release mechanism that was controlled dominantly by degradation. However, the incorporation of gelatin into the microsphere significantly extended the periods of molecule release from P(FAD-SA) microspheres, although the degradation profile of the microspheres themselves was quite similar to that of gelatin-free microspheres. It is possible that an interaction between FAD monomers and gelatin molecules causes continued release, even after the polymer matrix completely degrades (even after complete degradation, FAD monomers remain because of their poor water solubility). Thermal analysis of polyanhydride microspheres at different degradation stages demonstrated that a crystalline structure was formed between gelatin and the FAD monomers produced with microsphere degradation.(ABSTRACT TRUNCATED AT 250 WORDS)

Calorimetry, Differential Scanning↗
PubMedDate not supplied

Effect of tabletting compaction pressure on alginate microspheres.

Alginate and alginate-hydroxypropylmethylcellulose (HPMC) microspheres were prepared by the emulsification method. The compaction of microspheres for producing tablet dosage forms raises concerns about possible damage to microsphere walls with subsequent unpredictable dissolution rates. The effect of different compaction pressures on the integrity of the microspheres was investigated. The addition of a diluent, microcrystalline cellulose (MCC), was required to make compacts containing alginate and alginate-HPMC microspheres. Compacts containing alginate-HPMC (7:3) microspheres had the highest crushing strength followed by compacts containing alginate-HPMC (9:1) microspheres and alginate microspheres. However, compact crushing strength did not vary significantly with increased compaction pressures over the range of compaction pressures investigated. Differences in the drug release profiles of the original non-compacted and compacted alginate and alginate-HPMC microspheres were slight and not marked. Although dentation and distortion of the microspheres were observed with increasing compaction pressures, the microspheres generally remained intact, with minimal rupture/fracture.

Alginates↗
PubMedDate not supplied

Effect of adding non-volatile oil as a core material for the floating microspheres prepared by emulsion solvent diffusion method.

Eudragit microspheres, to float in the gastrointestinal tract, were prepared to prolong a gastrointestinal transit time. To enhance their buoyancy, non-volatile oil was added to the dispersed phase. When an oil component was not miscible with water, over 90% was entrapped within the microspheres and prolonged the floating time of the microspheres. Depending on the solvent ratio, the morphologies of the microspheres were different and the best result was obtained when the ratio of dichloromethane:ethanol:isopropanol was 5:6:4. As the isopropanol portion increased, the time to form microspheres was delayed and the amount of fibre-like substance produced was decreased, due to the slow diffusion rate of the solvent. Compared with microspheres prepared without non-volatile oil, the release rate of the drug from microspheres was faster in all cases tested, except the microspheres containing mineral oil. The solubility of the drug in the non-volatile oil affected the release profiles of the drugs. The non-volatile oil tends to decrease the glass transition temperature of prepared microspheres and change the release profile. The internal morphology of the microspheres was slightly different depending on the entrapped oil phase used. Tiny spherical objects were present at the inner surface of microspheres and the inside of the shell.

Acrylates↗
PubMedDate not supplied

Positively charged gelatin microspheres as gastric mucoadhesive drug delivery system for eradication of H. pylori.

Gastric mucoadhesive drug delivery systems are very promising for eradication of Helicobacter pylori (H. pylori), a spiral bacterium that resides in the gastric mucus layer and at the mucus-epithelial cell interface. New positively charged biodegradable microspheres were prepared using aminated gelatin by surfactant-free emulsification in olive oil, followed by a cross-linking reaction with glutaraldehyde. The amino group contents of the modified gelatin and the microspheres were determined using a 2,4,6-trinitrobenzenesulfonic acid method. With the increase of glutaraldehyde concentration, the amino group content of the microspheres decreased accordingly. The influence of glutaraldehyde concentration, cross-linking reaction time, drug-loading patterns, and type of release media on the in vitro release characteristics of amoxicillin from the microspheres was investigated. Amoxicillin release rate from the modified gelatin microspheres was significantly reduced compared with that from gelatin microspheres. Furthermore, the release was decreased with the increase of glutaraldehyde concentration and/or cross-linking time. On the other hand, a faster release was observed in a lower pH release medium and/or using a lower pH solution for amoxicillin loading. The gastric mucoadhesive properties of the microspheres were evaluated using RITC-labeled microspheres in an isolated rat stomach. The gastric mucoadhesion of the modified gelatin microspheres was markedly improved compared with that of gelatin microspheres. The modified gelatin microsphere proves to be a possible candidate delivery system for the effective eradication of H. pylori.

Adhesives↗