Biomedical subjects

Andreas Bernkop-Schnürch

Publications and source records attributed to Andreas Bernkop-Schnürch.

At least 19 recordsLinked to original sources

PubMed2007

Transport characteristics of a beta sheet breaker peptide across excised bovine nasal mucosa.

The purpose of the present study was to investigate the permeation characteristics of the beta sheet breaker peptide AS 602704 (BSB) on excised bovine nasal mucosa using an Ussing chamber model. The influence of various absorption enhancers such as sodium cholate, sodium dodecyl sulfate (SDS), cetrimidum, sodium caprate, Na(2)EDTA, polycarbophil (PCP), the thiomer conjugate polycarbophil-cysteine (PCP-Cys), and poly-l-arginine (poly-l-arg; 100 kDa) was evaluated. Additionally, the influence of temperature and pH on the transport rate as well as the stability of the peptide drug against enzymatic degradation were investigated in vitro. The effective permeability coefficient (P(eff)) of BSB in Krebs-Ringer-buffer (KRB) pH 7.4 was (1.89 +/- 0.44)* 10-5, while in the presence of sodium caprate (0.5%) a P(eff) of (9.58 +/- 1.82)*10-5 was achieved. Rank order of enhancement ratio was sodium caprate > SDS > sodium cholate > Na(2)EDTA > poly-L-arg = PCP-Cys. In case of cetrimidum and PCP even a decrease in the absorption of BSB was determined. Na2EDTA reduced the enzymatic degradation of BSB when exposed to a nasal tissue homogenate by more than the half. An increased lipophilicity of BSB because of a more acidic milieu (pH 5.5) did not lead to an increased transcellular transport. Permeation studies carried out at 4 degrees C compared to 37 degrees C demonstrated a temperature dependent permeation behaviour suggesting an additional active carrier mediated transport. The results obtained within these studies should facilitate the development of a nasal delivery system for AS 602704 for the treatment of Alzheimer's disease.

Administration, Intranasal↗

PubMed2006

Development and in vitro evaluation of a thiomer-based nanoparticulate gene delivery system.

Chitosan-thiobutylamidine was developed and evaluated as a novel tool for gene delivery. The conjugate, displaying 299.1+/-11.5 micromol free thiol groups per gram polymer, formed coacervates with pDNA at a mean size of 125 nm and a zeta potential of +9 mV. Thiol groups, being susceptible for oxidation, were immobilised on the polymeric backbone of chitosan in order to introduce the property of extracellular stability and intracellular pDNA release by forming reversible disulfide bonds. The integrity of the new particles was compared to unmodified chitosan under simulated physiological conditions. Within 10h, pDNA was completely released from chitosan-DNA particles while only 12% were released from the thiomer-based particles. At pH 7, the amount of thiol groups significantly (p<0.05) decreased by more than 25% within 6h. In contrast, in a reducing environment as found intracellularly, chitosan-thiobutylamidine-DNA nanoparticles dissociated continuously, liberating approximately 50% of pDNA within 3h. Transfection studies performed in a Caco2 cell culture evinced the highest efficiency for chitosan-thiobutylamidine-DNA nanoparticles in combination with a glycerol shock solution. The combination of improved stability, enhanced pDNA release under reducing conditions, and higher transfection efficiency identifies chitosan-thiobutylamidine as a promising new vector for gene delivery.

Butylamines↗

PubMed2006

In vivo comparison of various polymeric and low molecular mass inhibitors of intestinal P-glycoprotein.

Several polymers have been reported to modulate drug absorption by inhibition of intestinal P-glycoprotein (P-gp). The aim of the present study was to provide a direct in vivo comparison of delivery systems based on Pluronic P85, Myrj 52 and chitosan-4-thiobutylamidine (Ch-TBA) in vivo in rats, using rhodamine-123 (Rho-123) as representative P-gp substrate. Furthermore, the postulated low molecular mass P-gp inhibitors 6-mercaptopurine and reduced glutathione (GSH) were evaluated in vitro and in vivo. In vitro, the permeation enhancing effect of 6-mercaptopurine, GSH, Pluronic P85, Myrj 52, and the combination of Ch-TBA with GSH was evaluated by using freshly excised rat intestinal mucosa mounted in Ussing-type diffusion chambers. In comparison to buffer only, Rho-123 transport in presence of 100 microm 6-mercaptopurine, 0.5% (w/v) GSH, 0.5% (w/v) Pluronic P85, 0.5% (w/v) Myrj 52 and the combination of 0.5% (w/v) Ch-TBA/ 0.5% (w/v) GSH, was 2.1, 1.6, 1.9, 1.8, 3.0-fold improved, respectively. In vivo in rat, enteric-coated tablets based on Pluronic P85, Myrj 52 or Ch-TBA/GSH increased the area under the plasma concentration time curve (AUC(0-12)) of Rho-123 1.6-fold, 2.4-fold, 4.3-fold, respectively, in comparison to control only. Contrariwise, the low molecular mass excipients 6-mercaptopurine and GSH showed no significant effect in vivo at all. This in vivo study showed that polymeric P-gp inhibitors and especially the delivery system based on thiolated chitosan significantly increased the oral bioavailability of P-gp substrate Rho-123.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2006

Development of a novel method for the preparation of thiolated polyacrylic acid nanoparticles.

PURPOSE: To develop a novel method for the preparation of thiolated polyacrylic acid nanoparticles via ionic gelation. MATERIALS AND METHODS: In a first step nanoparticles were generated by ionotropic gelation of polyacrylic acid (PAA) of three different molecular weights (100, 240 and 450 kDa) and various cations including Ca2+, Mg2+, Zn2+, Al3+ and Fe3+. Via in vitro characterization of the particles (particle size, size distribution and zeta potential) the optimal preparation conditions were established. Taking into consideration, that thiolated polyacrylic acid (PAA-Cys) displays higher mucoadhesive and permeation enhancing properties than unmodified PAA, PAA-Cys nanoparticles were produced in the same manner with Ca2+, as the most promising results concerning particle size and stability of particles could be achieved with this ionic crosslinker. The nanoparticles were stabilized via the formation of inter- and intrachain disulfide bonds within these particles due to oxidation with H2O2. Ca2+ was removed proximately by the addition of EDTA and exhaustive dialysis. RESULTS: Using the preparation method described above PAA-Cys nanoparticles of a mean diameter of about 220 nm (PAA(100)-Cys), 250 nm (PAA(240)-Cys) and 295 nm (PAA(450)-Cys) can be generated. In comparison to PAA nanoparticles ionically crosslinked with Ca2+, the removal of the crosslinker Ca2+ from PAA-Cys particles led to a nearly three-fold decrease in the zeta potential, from about -7 up to -20 mV. Apart from this advantage, covalently crosslinked PAA-Cys nanoparticles were more firm as they remained stable when incubated in hydrochloride solution, whereas ionically crosslinked particles dissolved at pH lower than 5. CONCLUSIONS: This novel nanoparticulate delivery system seems to be a promising vehicle for the administration of therapeutic proteins, genes and antigens via mucosal membranes.

Acrylic Resins↗

PubMed2006

Inhibition of malarial topoisomerase II in Plasmodium falciparum by antisense nanoparticles.

New effective antimalarial agents are urgently needed due to increasing drug resistance of Plasmodium falciparum. Phosphorothioate antisense oligodeoxynucleotides (ODNs) silencing of malarial topoisomerase II gene have shown to possess promising features as anti malarial agents. In order to improve stability and to increase intracellular penetration, ODNs were complexed with the biodegradable polymer chitosan to form solid nanoparticles with an initial diameter of approximately 55 nm. The particle zetapotential depended on the chitosan/ODN mass ratio. Nanoparticles with mass ratio of 2:1 displayed a positive surface charge (+15 mV) whereas particles with 1:1 mass ratio were negatively charged (-20 mV). Additionally nanoparticles were found to protect ODNs from nuclease degradation. P. falciparum K1 strain was exposed to the chitosan/ODN-nanoparticles for 48 h in order to examine the effects of chitosan/antisense (AS) and chitosan/sense (S) oligodeoxynucleotide nanoparticles on malaria parasite growth. Both negatively and positively charged antisense nanoparticles as well as free antisense ODNs (in a final concentration of 0.5 microM) showed sequence specific inhibition compared with sense sequence controls. However, nanoparticles were much more sequence specific in their antisense effect than free ODNs. Nanoparticles with negative surface charge exhibited a significantly stronger inhibitory effect ( approximately 87% inhibition) on the parasite growth in comparison to the positive ones ( approximately 74% inhibition) or free ODNs ( approximately 68% inhibition). This is the first study demonstrating the susceptibility of P. falciparum to antisense nanoparticles.

Animals↗

PubMed2006

In vivo evaluation of an oral delivery system for P-gp substrates based on thiolated chitosan.

Recently, thiolated polymers, so called thiomers, have been reported to modulate drug absorption by inhibition of intestinal P-glycoprotein (P-gp). The aim of the present study was to provide a proof-of-principle for a delivery system based on thiolated chitosan in vivo in rats, using rhodamine-123 (Rho-123) as representative P-gp substrate. In vitro, the permeation enhancing effect of unmodified chitosan, chitosan-4 thiobutylamidine (Ch-TBA) and the combination of Ch-TBA with reduced glutathione (GSH) was evaluated by using freshly excised rat intestinal mucosa mounted in Ussing-type chambers. In comparison to buffer only, Rho-123 transport in presence of 0.5% (w/v) chitosan, 0.5% (w/v) Ch-TBA and the combination of 0.5% (w/v) Ch-TBA/0.5% (w/v) GSH, was 1.8-fold, 2.6-fold, 3.8-fold improved, respectively. Furthermore, enteric-coated tablets based on unmodified chitosan or Ch-TBA/GSH, were investigated in vivo. In rats, the Ch-TBA/GSH tablets increased the area under the plasma concentration time curve (AUC0-12) of Rho-123 by 217% in comparison to buffer control and by 58% in comparison to unmodified chitosan. This in vivo study showed that a delivery system based on thiolated chitosan significantly increased the oral bioavailability of P-gp substrate Rho-123.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2006

Elaboration and characterization of thiolated chitosan-coated acrylic nanoparticles.

The aim of the present work was to investigate the use of thiolated chitosan in the development of polysaccharide-coated nanoparticles in order to confer specific functionality to the system. After chemical modification of commercial and hydrolysed chitosan (400,000 and 9400 g/mol respectively), thiolated chitosans were used to elaborate particles in the nano-range. They were characterized in terms of size and surface charge measurement. Both analysis showed nanoparticles of mean hydrodynamic diameter around 200 nm and positive zeta potential values, indicating the presence of the cationic polysaccharide at the nanoparticle surface. Moreover, the Ellman's reaction was used to demonstrate the presence of thiol groups at the particle surface. The observation of nanoparticles by scanning electronic microscopy (SEM) showed spherical nanoparticles for all formulations. This new system, combining both the advantages of thiolated polymers and colloidal particles can be proposed as an original drug carrier system for mucosal delivery of biotechnology products.

Chitosan↗

PubMed2006

Thiomers: preparation and in vitro evaluation of a mucoadhesive nanoparticulate drug delivery system.

It was the aim of this study to develop a mucoadhesive nanoparticulate delivery system. Nanoparticles were generated by in situ gellation of the thiomer chitosan-4-thiobutylamidine (chitosan-TBA) with tripolyphosphate (TPP) followed by stabilization via the formation of inter- and intrachain disulfide bonds by oxidation with H(2)O(2) in various concentrations. Afterwards TPP was removed by exhaustive dialysis at pH 1-2. Incorporation of the model compound fluorescein diacetate (FDA) was achieved by incubation of this fluorescence marker, dissolved in acetonitrile, with aqueous particle suspensions for 1h at room temperature. Mucoadhesion studies were performed on porcine intestinal mucosa. Results showed that the preparation method described above leads to nanoparticles of a mean diameter of 268+/-15 nm and a FDA load of 2%. Due to the removal of the anionic crosslinker TPP, the zeta potential of the nanoparticles was raised from 4+/-1 up to 19+/-2 mV without loosing stability of the nanoparticles. The more H(2)O(2) was added to the particles, the more inter- and intrachain disulfide bonds were formed. The more thiol groups were oxidized within the particles, however, the lower was the improvement in mucoadhesive properties. Nevertheless, even when 91% of all thiol groups on the nanoparticles were oxidized, their mucoadhesive properties were still twice as high as the mucoadhesive properties of unmodified nanoparticles. Thiolated chitosan nanoparticles show a two-fold higher zeta potential (I), improved stability (II) and more than doubled mucoadhesive properties (III) than corresponding unmodified chitosan nanoparticles. Therefore, they seem to be advantageous over ionically crosslinked chitosan nanoparticles.

Adhesiveness↗

PubMed2006

Development of a novel method for the preparation of submicron particles based on thiolated chitosan.

It was the aim of this study to develop a simple method for the production of thiolated chitosan particles without being ionically crosslinked. In the first step, thiolated chitosan was ionically gelated with tripolyphosphate (TPP) and sulphate in aqueous solution forming submicron particles and microparticles, respectively. In the next step, thiol groups in and on the particles were partially oxidized forming stabilizing inter- and intramolecular disulfide bonds. As the degree of oxidation can be controlled during the production process, the share of thiol and disulfide groups can be adjusted on demand. Thereafter the polyanions were removed. Utilizing this novel preparation method stable particles of a mean size of 366 +/- 30 nm and a zeta potential of around + 11.3 +/- 1.3 mV can be produced using TPP as ionic crosslinker. On average 83% of all thiol groups were oxidized. In contrast, particles did not remain stable after removing sulphate as temporary auxiliary ionic crosslinker. Neither ionically nor covalently crosslinked particles were degraded by lysozyme under physiological conditions. Utilizing the novel method described here allows a simple production of thiolated chitosan particles without losing the cationic charge of chitosan.

Biodegradation, Environmental↗

PubMed2006

Thiolated chitosans: design and in vivo evaluation of a mucoadhesive buccal peptide drug delivery system.

PURPOSE: Intravenous application of pituitary adenylate cyclase-activating polypeptide (PACAP) has been identified as a promising strategy for the treatment of type 2 diabetes. To generate a more applicable formulation, it was the aim of this study to develop a sustained buccal delivery system for this promising therapeutic peptide. METHODS: 2-Iminothiolane was covalently bound to chitosan to improve the mucoadhesive and permeation-enhancing properties of chitosan used as drug carrier matrix. The resulting chitosan-4-thiobutylamidine conjugate was homogenized with the enzyme inhibitor and permeation mediator glutathione (gamma-Glu-Cys-Gly), Brij 35, and PACAP (formulation A). The mixture was lyophilized and compressed into flat-faced discs (18 mm in diameter). One formulation was additionally coated on one side with palm wax (formulation B). Tablets consisting of unmodified chitosan and PACAP (formulation C) or of unmodified chitosan, Brij 35, and PACAP (formulation D) served as controls. Bioavailability studies were performed in pigs by buccal administration of these test formulations. Blood samples were analyzed via an ELISA method. RESULTS: Formulations A and B led to an absolute bioavailability of 1%, whereas PACAP did not reach the systemic circulation when administered via formulations C and D. Moreover, in the case of formulations A and B, a continuously raised plasma level of the peptide drug being in the therapeutic range could be maintained over the whole period of application (6 h). Formulations A and B were removed by moderate force from the buccal mucosa after 6 h, whereas formulations C and D detached from the mucosa 4 h after application. CONCLUSION: The study reveals this novel mucoadhesive delivery system to be a promising approach for buccal delivery of PACAP.

Adhesiveness↗

PubMed2006

In vivo evaluation of a nasal insulin delivery system based on thiolated chitosan.

The aim of this study was the preparation and in vivo evaluation of a nasal insulin delivery system based on thiolated chitosan. 2-Iminothiolane was covalently attached to chitosan. The resulting conjugate (chitosan-TBA) exhibited 304.9 +/- 63.5 micromol thiol groups per gram polymer. Microparticles were prepared via a new precipitation-micronization technique. The microparticulate delivery system comprised insulin, reduced glutathione and chitosan-TBA (Chito-TBA/Ins) or unmodified chitosan (Chito/Ins) and control microparticles were composed of insulin and mannitol (Mannitol/Ins). Due to a hydration process the size of Chito-TBA/Ins and Chito/Ins microparticles increased in phosphate buffer pH 6.8 2.6- and 2.2-fold, respectively. Fluorescent-labeled insulin-loaded chitosan-TBA microparticles showed a controlled release over 4 h. Chito-TBA/Ins administered nasally to rats led to an absolute bioavailability of 6.9 +/- 1.5%. The blood glucose level decreased for more than 2 h and the calculated absolute pharmacological efficacy was 4.9 +/- 1.4%. Chito/Ins, in comparison, displayed a bioavailability of 4.2 +/- 1.8% and a pharmacological efficacy of 0.7 +/- 0.6%. Mannitol/Ins showed a bioavailability of 1.6 +/- 0.4% and no reduction of the blood glucose level at all. According to these findings microparticles comprising chitosan-TBA seem to have substantial higher potential for nasal insulin administration than unmodified chitosan.

Administration, Intranasal↗

PubMed2006

Improved synthesis and in vitro characterization of chitosan-thioethylamidine conjugate.

The aim of this study was to establish improved reaction conditions for the synthesis of chitosan-thioethylamidine (Ch-TEA) conjugate and to evaluate the properties of the obtained Ch-TEA conjugate. The influence of different factors on the coupling reaction, such as concentration of chitosan solution, employment of reducing agent and deprotection of S-acetyl groups, was evaluated. The cohesive properties and stability of the obtained conjugate were evaluated by disintegration test and by oxidation experiments, respectively. The adhesive properties of Ch-TEA conjugate were evaluated in vitro on freshly excised porcine mucosa via tensile studies and the rotating cylinder method. The permeation-enhancing effect of Ch-TEA conjugate was evaluated in Ussing-type chambers by using rhodamine 123 as model compound. The resulting conjugate displayed 225 micromol immobilized free thiol groups and 102 micromol disulfide bonds per gram polymer. The degree of modification depends mostly on the chitosan concentration employed and the deprotection of S-acetyl groups with hydroxylamine. During oxidation studies the amount of thiol groups decreased by 61%. Disintegration studies of tablets comprising Ch-TEA demonstrated stability for 48 h. In tensile studies, the total work of adhesion of the conjugate was determined to be 5.1-fold increased in comparison to unmodified chitosan. Results from the rotating cylinder method showed more than a 13-fold increase in the adhesion time of thiolated chitosan versus unmodified chitosan. The apparent permeability coefficient (Papp) of the system 0.5% (w/v) Ch-TEA conjugate with 5% (w/v) glutathione was calculated to be 5.35 x 10(-8)cm/s, while the Papp value of the system 0.5% (w/v) unmodified chitosan was 1.73 x 10(-8)cm/s. These features should render Ch-TEA useful as an excipient for various drug delivery systems.

Adhesiveness↗

PubMed2006

Degradation of teriparatide by gastro-intestinal proteolytic enzymes.

Teriparatide, a recombinant parathyroid hormone (1-34) is the first approved agent for the treatment of osteoporosis that stimulates new bone formation. Currently, the drug is administered daily by s.c. injection. Because of the obvious advantages of oral teriparatide administration, the development of such a delivery system would be of great benefit. Besides other barriers, the enzymatic barrier caused by gastro-intestinal (GI) proteolytic enzymes is believed to be responsible for negligible teriparatide oral bioavailability. It was therefore the aim of the study to evaluate the stability of teriparatide towards a variety of GI proteases under physiological conditions. Results indicate that teriparatide is entirely degraded by trypsin, chymotrypsin and pepsin within 5 min. In contrast, even after 3 h of incubation with elastase about 85% of undegraded teriparatide could still be detected. Within an incubation period of 3 h in the presence of rat small intestinal mucosa, approximately half of the teriparatide was degraded. Experiments with isolated aminopeptidase N demonstrated that this membrane bound peptidase is primarily involved in the degradation process. Results gained from and recorded in this study provide a precise characterisation of the enzymatic barrier for oral teriparatide administration and represents a prerequisite for the development of oral teriparatide delivery systems.

Amino Acid Sequence↗

PubMed2006

Oral peptide delivery: are there remarkable effects on drugs through sulfhydryl conjugation?

In oral peptide delivery, the gap between convenient administration and low blood concentration has to be minimized. We found that oral peptide drugs have not only to pass the various commonly known barriers encountered with the gastrointestinal tract but that these drugs, under certain conditions, have also to be seen as redox partners for thiol bearing substrates. The interaction of glutathione (GSH) with peptides via thiol-disulfide exchange reactions was investigated for three peptides, vasotocin, oxytocin and octreotide. The extent of thiol-disulfide exchange reactions was investigated by liquid chromatography (LC) and further confirmed by hyphenation to electrospray ionization (ESI) and MALDI-TOF mass spectrometry (MS). We found that the presence of aromatic amino acid residues in the neighbourhood of the disulfide bond minimizes the thiol-disulfide interaction: oxytocin was degraded more than 80% with 1% reduced glutathione at pH 3.0 and vasotocin more than 40% under the same conditions. In the case of octreotide no interaction with GSH was observed. The obtained results revealed that thiol-disulfide exchange reactions have an important impact on the alteration of peptide drugs and proteins in the gastrointestinal tract.

Administration, Oral↗

PubMed2006

The potential of cystine-knot microproteins as novel pharmacophoric scaffolds in oral peptide drug delivery.

Within this study, the potential of three clinically relevant microproteins (SE-AG-AZ, SE-EM and SE-EP) with cystine-knot architecture as pharmacophoric scaffolds for oral peptide delivery was investigated. Cystine-knot microproteins (CKM) were analysed regarding their stability towards the most important gastrointestinal secreted and membrane bound proteases in physiological concentrations. In addition, their permeation behaviour through freshly excised rat intestinal mucosa as well as important parameters such as aggregation behaviour, stability in rat plasma and isoelectric point were evaluated and compared to the properties of the model peptide drugs bacitracin and insulin. Aggregation studies indicate that under physiological conditions between 25 and 70% of the CKMs occur as monomers, whereas the rest forms di- and trimers. Pepsin and elastase cause no or only minor degradation to CKMs, whereas trypsin and chymotrypsin degrade CKMs extensively. Removing the theoretical chymotrypsin cleavage site from a CKM, however, led to stabilization towards this protease. Two of the three evaluated CKMs are stable against membrane bound proteases. P(app) values were determined to be 5.96 +/- 0.98 x 10(-6) and 6.63 +/- 0.47 x 10(-6) cm/s. In conclusion, this study indicates that CKM are promising novel pharmacophoric scaffolds for oral peptide delivery.

Administration, Oral↗

PubMed2006

Oral gene delivery: Strategies to improve stability of pDNA towards intestinal digestion.

PURPOSE: Gastrointestinal (GI) nucleases are responsible for a rapid presystemic degradation of orally administered transgenes. Within the current study, the activity of these degrading enzymes as well as the effect of various nuclease inhibitors on the degradation process were evaluated in order to assess their potential as auxiliary agents in oral gene delivery. METHODS: Digestion assays of pDNA with DNaseI and in GI juices were performed in absence and presence of inhibitors. Consequently, a chitosan conjugate with covalently bound ethylendiaminetetraacetic acid disodium salt dihydrat (EDTA) was synthesized and its nuclease inhibitory properties were evaluated. RESULTS: Small intestinal juice was shown to possess a nuclease activity per millilitre corresponding to 0.02 Kunitz units of DNaseI. Inhibition studies revealed that inhibitory activity followed the ranking: EDTA > sodium dodecyl sulfate (SDS) > aurintricarboxylic acid (ATA) > poly (acrylic acid) > cysteine. The chitosan-EDTA conjugate offered good nuclease inhibiting properties. CONCLUSION: This study determined the nuclease activity of native porcine small intestinal juice as well as enterocytes homogenate. Moreover, several promising strategies to overcome this enzymatic barrier were identified.

Administration, Oral↗

PubMed2005

Thiolated chitosan microparticles: a vehicle for nasal peptide drug delivery.

The goal of this study was to develop a microparticulate delivery system based on a thiolated chitosan conjugate for the nasal application of peptides. Insulin was used as model peptide. For thiolation of chitosan 2-iminothiolane was covalently linked to chitosan. The resulting chitosan-TBA (chitosan-4-thiobutylamidine) conjugate featured 304.89+/-63.45 micromol thiol groups per gram polymer. 6.5% of these thiol groups were oxidised. A mixture of the chitosan-TBA conjugate, insulin and the permeation mediator reduced glutathione were formulated to microparticles. Control microparticles comprised unmodified chitosan and insulin. As second control served mannitol-insulin microparticles. All microparticulate systems were prepared via the emulsification solvent evaporation technique. In 100 mM phosphate buffer pH 6.8 chitosan-TBA-insulin microparticles swelled 4.39+/-0.52-fold in size, whereas chitosan based microparticles did not swell at all. Chitosan-TBA microparticles showed a controlled release of fluorescein isothiocyanate (FITC)-labelled insulin over 6 h. Nasal administered chitosan-TBA-insulin microparticles led to an absolute bioavailability of 7.24+/-0.76% (means+/-S.D.; n=3) in conscious rats. In contrast, chitosan-insulin microparticles and mannitol-insulin microparticles exhibited an absolute bioavailability of 2.04+/-1.33% and 1.04+/-0.27%, respectively (means+/-S.D.; n=4). Because of these results microparticles comprising chitosan-TBA and reduced glutathione seem to represent a useful formulation for the nasal administration of peptides.

Administration, Intranasal↗

PubMed2005

Evaluation of the potential of air jet milling of solid protein-poly(acrylate) complexes for microparticle preparation.

It was the aim of this study to evaluate the potential of air jet milling for the preparation of protein-loaded microparticles in industrial quantities. The model protein horseradish peroxidase was incorporated via co-precipitation in carbomer (NaC934P) (1:100) and a poly(methacrylate) (Eudragit L100-55) (1:100) used as carrier matrix. Co-precipitation of the model protein and each polymer in aqueous solution was achieved either by a pH-shift or by the addition of various non-solvents. Dried protein/polymer complexes (desiccator under vacuumization at 4 degrees C with silica blue gel) were ground with an air jet mill and resulting microparticles were investigated regarding protein load, remaining protein activity, size distribution and shape. Results of this study showed that the polymer used and the method of co-precipitation has a great impact on protein load. Using carbomer a maximum protein load of 60 +/- 1% was achieved, whereas in case of Eudragit L100-55 the maximum was 78 +/- 5% (means +/- SD; n = 3-4). Using petroleum ether, isopropanol or tetrahydrofurane as non-solvents led to significantly higher protein loads than a pH-shift from 7 to 5, 4 and 3.5, respectively. Determination of the remaining protein activity after milling showed, that the grinding air pressure (GAP) has a major impact on protein stability. In case of Eudragit L100-55 at a GAP of 4.5 bar peroxidase activity was almost completely lost, whereas 42 +/- 1% loss in activity was determined at a GAP of 2.5 bar. The mean particle size of protein/carbomer and protein/poly(methacrylate) particles was determined to be 3.6-5.2 and 4.5-8.7 microm at a GAP of 2.5 bar and 2.7-3.1 and 2.4-3.1 microm at a GAP of 4.5 bar, respectively. Generally, 90% of all particles were in the range of 3-16 microm. All particles were of spherical shape exhibiting a non-porous surface. According to these results, air jet milling seems to represent a novel method for the large-scale production of protein drug loaded microparticles.

Acrylic Resins↗