Incorporation of water-soluble drugs in albumin microspheres

Development of kojic acid loaded collagen-chitosan nanoparticle as skin lightener product: in vitro and in vivo assessment

In the present study, an ionic gelation and ultrasonic approach was performed to produce kojic acid (KA) loaded chitosan(CS)/collagen(CN) nanoparticle(NP) (CSCN-NP) which aimed to increase the dermal delivery and anti-pigmentation effect. To optimize the CSCN-NP the effect of the amount of CN was investigated. The results showed that increasing CN from 0 to 500 mg increased the mean particle size and entrapment efficiency of KA-CSCN-NP from 266.07 ± 9.30 nm to 404.23 ± 9.44 nm and 17.37 ± 2.06% to 82.34 ± 2.16%, respectively. Differential scanning calorimetry confirmed the amorphous form of KA in CSCN-NP, while scanning electron microscopy revealed that the nanoparticles were spherical. There was no chemical interaction between KA and the other components base on attenuated total reflectance-Fourier transform infrared spectroscopy. The skin permeability test showed that KA-CSCN-NP gel delivered more KA to the dermal layers (29.16 ± 1.67% or 537.26 ± 537.26 μg/cm2) and receiver compartment (15.04 ± 1.47% or 277.15 ± 27.22 μg/cm2) compared to KA plain gel. In vitro cytotoxicity assay demonstrated that the improved KA-CSCN-NP was non-toxic. Dermal irritating test on Wistar rats showed that the KA gel was non-irritating. Furthermore, KA-CSCN-NP was found to inhibit melanin formation to a greater extent than free KA and significantly inhibited L-dopa auto-oxidation (94.80 ± 2.41%) compared to pure kojic acid solution (75.28 ± 3.22%). The observations of this study revealed that the produced KA-CSCN-NP might be used as a potential nano-vehicle for KA dermal administration, thereby opening up innovative options for the management of hyper-melanogenesis problems.

Surfactant-Free Preparation of Biodegradable Hydrogel Microspheres for Protein Release

The preparation of biodegradable hydrogel microspheres in the absence of surfactants was carried out by a two-step procedure which involved the formation of non-crosslinked microspheres from gelatin based on its inherent gelation nature at low temperatures and the subsequent glutaraldehyde (GA) crosslinking. The size of the microspheres was controlled in the range of 3 to 100 μm by changing the concentration of gelatin or GA, the emulsification method, and the crosslinking time. Neutral aqueous solutions of proteins with different isoelectric points (IEPs) and molecular weights (Mws) were infused into freeze-dried hydrogel microspheres to produce protein-incorporated gelatin microspheres. In vitro protein release from the microspheres depended on the protein's IEP but not on the Mw. The incorporated basic proteins with IEPs > 7.0 were released initially from the acidic gelatin microspheres, followed by no substantial release, whereas a larger initial release of the incorporated acidic proteins with IEPs < 7.0 was observed. The basic gelatin microspheres exhibited an opposite relationship between proteins IEP and protein release. Noncharged dextran rapidly diffused out of acidic gelatin microspheres, irrespective of the Mw. These findings indicate that an ionic interaction with gelatin constituted hydrogel microspheres prevented oppositely charged protein from being released from gelatin under in vitro non-degradation conditions.

Polymeric nanospheres modified with YIGSR peptide for tumor targeting

YIGSR peptide anchored pegylated nanospheres (YIGSR-SN) loaded with 5-fluorouracil (5-FU) were investigated for selective and preferential presentation of carrier contents at angiogenic endothelial cells over-expressing laminin receptors on and around tumor tissue and thus for assessing their targetability. Pegylated nanosphere (SN) without peptide conjugate were used for comparison. The average size of all nanosphere preparations prepared was approximately 108 nm and maximum drug entrapment was 68.5 +/- 5.2%. In vitro endothelial cell binding of nanospheres exhibited 8-fold higher binding of YIGSR-SN to HUVEC in comparison to the SN. Spontaneous lung metastasis and angiogenesis assays show that YIGSR peptide anchored nanospheres are significantly (p <or= 0.05) effective in the prevention of lung metastasis and angiogenesis compared to free 5-FU and SN. In therapeutic experiments, 5-FU, SN, and YIGSR-SN were administered intravenously on day 4 at the dose of 10 mg 5-FU/kg body weight to B16F10 tumor bearing BALB/c mice resulting in effective regression of tumors in YIGSR-SN compared with free 5-FU and SN. Results indicate that YIGSR peptide anchored pegylated nanospheres bearing 5-FU are significantly (p <or= 0.05) active against primary tumor and metastasis than the non-targeted pegylated nanospheres and free drug. Thus, YIGSR peptide anchored pegylated nanospheres hold potential of targeted cancer chemotherapeutics.

Albumin-based nanoparticles as magnetic resonance contrast agents: I. Concept, first syntheses and characterisation

To develop a platform for molecular magnetic resonance imaging, we prepared gadolinium-bearing albumin-polylactic acid nanoparticles in the size range 20-40 nm diameter. Iterative cycles of design and testing upscaled the synthesis procedures to gram amounts for physicochemical characterisation and for pharmacokinetic testing. Morphological analyses showed that the nanoparticles were spheroidal with rough surfaces. Particle sizes were measured by direct transmission electron microscopical measurements from negatively contrasted preparations, and by use of photon correlation spectroscopy; the two methods each documented nanoparticle sizes less than 100 nm and generally 10-40 nm diameter, though with significant intrabatch and interbatch variability. The particles' charge sufficed to hold them in suspension. HSA retained its tertiary structure in the particles. The nanoparticles were stable against turbulent flow conditions and against heat, though not against detergents. MRI imaging of liquid columns was possible at nanoparticle concentrations below 10 mg/ml. The particles were non-cytotoxic, non-thrombogenic and non-immunogenic in a range of assay systems developed for toxicity testing of nanoparticles. They were micellar prior to lyophilisation, but loosely structured aggregated masses after lyophilisation and subsequent resuspension. These nanoparticles provide a platform for further development, based on non-toxic materials of low immunogenicity already in clinical use, not expensive, and synthesized using methods which can be upscaled for industrial production.

Targeted brain delivery of AZT via transferrin anchored pegylated albumin nanoparticles

Hydrophilic drugs/peptides have poor cross Blood-brain permeability. Various drug delivery systems with diverse surfacial characteristics have been reported for effective translocation of drugs across Blood-brain barrier. In present investigation, the potential of engineered albumin nanoparticles was evaluated for brain specific delivery after intravenous administration. Long circulatory PEGylated albumin nanoparticles encapsulating water-soluble antiviral drug azidothymidine (AZT) were prepared by ultra-emulsification method using chemical cross-linking by glutaraldehyde. Surface of the PEGylated nanoparticles was modified by anchoring transferrin as a ligand for brain targeting. Nanoparticles were characterized for their size, polydispersity, surfacial charge, drug loading and in vitro drug release. Fluorescence studies revealed the enhanced uptake of transferrin-anchored nanoparticles in the brain tissues when compared with unmodified nanoparticles. In vivo evaluation was carried out on albino rats to evaluate tissue distribution of engineered nanoparticles after intravenous administration. A significant ((*)P < 0.01) enhancement of brain localization of AZT was observed for transferrin anchored pegylated albumin nanopariticles (Tf-PEG-NPs). Hence, the specific role of transferrin ligand on nanoparticles for brain targeting was confirmed.

Preparation, characterization and in vivo distribution of terbutaline sulfate loaded albumin microspheres

Terbutaline sulfate is widely used as a bronchodilator for the treatment of bronchial asthma, chronic bronchitis and emphysema. As it has a short biological half-life, a long acting terbutaline sulfate formulation is desirable to improve patient compliance. Bovine serum albumin microspheres were prepared by an emulsion polymerization method using glutaraldehyde as the crosslinking agent. All microspheres were spherical and smooth with the mean particle size in the range of 22-30 microm. Drug release from the BSA microspheres displayed a biphasic pattern characterized by an initial fast release, followed by a slower release. The released amount was decreased with an increase in the glutaraldehyde concentration. In the absence of trypsin, the time required for complete degradation of microspheres was increased from 144 to 264 h when the glutaraldehyde concentration increased from 0.1 to 0.7 ml. In the presence of trypsin, a linear relationship was obtained between the degradation rates and trypsin concentrations, indicating that saturation was not reached under the experimental conditions. Biodistribution studies indicated that the degree of uptake by the lungs was higher than that of the other organs. All these results demonstrated that terbutaline sulfate loaded microspheres can be used for passive lung targeting.

Adjuvancy enhancement of muramyl dipeptide by modulating its release from a physicochemically modified matrix of ovalbumin microspheres. II. In vivo investigation

In the present study, sustaining the release of adjuvants was investigated using microspheres as a means to increase the immune response (i.e. efficacy) and, ultimately, to reduce adverse effects to vaccine components. To date, most attempts have focused on sustaining the release of antigens. The utility of currently used vaccine adjuvants may be improved by sustaining their release. The development, modification and characterization of a two-component microsphere vaccine delivery system was demonstrated in our previous report [Puri et al., J. Control. Release (2000) in press]. Briefly, ovalbumin (OVA) was utilized as the model antigen (Ag) and delivery matrix and MDP or threonyl-MDP served as the model adjuvants. The release pattern of MDP was modulated from a physicochemically modified matrix of OVA microspheres (OVA-MSs). The purpose of the present study was to evaluate the adjuvancy of MDP in mice by modulating its release from OVA-MSs. Mice were immunized intradermally (i.d.) with various preparations of OVA-MSs, using a single-shot-immunization technique. Positive and negative control preparations were evaluated as well. An inverse relationship was observed between the in vitro release rate of MDP and the in vivo OVA-specific IgG antibody (Ab) immune response in mice. These results demonstrated that modulating the release pattern of MDP or threonyl-MDP enhanced their adjuvant effect. In conclusion, the current results demonstrate that the sustained and controlled release of adjuvants is extremely important for inducing a high level and prolonged period of immunostimulation while potentially minimizing therapy-limiting adverse effects.

Adjuvancy enhancement of muramyl dipeptide by modulating its release from a physicochemically modified matrix of ovalbumin microspheres. I. In vitro characterization

The weak immunogenicity of subunit vaccines has necessitated research into the development of novel adjuvants and methods to enhance the adjuvancy associated with vaccine delivery systems. The purpose of the present study was to modulate the release of muramyl dipeptide (MDP) from a physicochemically modified matrix of ovalbumin microspheres (OVA-MSs). A two-component MS vaccine delivery system was fabricated, which utilized OVA as the antigen and delivery matrix, and MDP as the adjuvant. The MSs were prepared from OVA using a water/oil emulsion method, followed by suspension cross-linking using glutaraldehyde. The MS matrix was modified with respect to the degree of cross-linking by varying the concentration of glutaraldehyde and matrix density, a function of disulfide-bond formation. The modifications in the MS matrix were characterized using SDS-PAGE, scanning electron microscopy, differential scanning calorimetry, and thin layer wicking (TLW). The in vitro release of MDP and OVA from the various preparations of OVA-MSs exhibited triphasic and biphasic profiles, respectively. The degree of cross-linking and the matrix density were found to be significant physicochemical parameters that affected the release profiles of MDP and OVA through two mechanisms: controlled surface erosion and bulk degradation of the MSs.

An investigation of the intradermal route as an effective means of immunization for microparticulate vaccine delivery systems

Among the common routes of parenteral immunization, the skin is the only site that can function as an immune organ. Skin-associated lymphoid tissue contains specialized cells that enhance the immune response. The intercellular space in the skin interstitium provides a connection to the lymphatic capillaries and vessels that terminate in peripheral immune organs like the lymph nodes and spleen. The potential of intradermal immunization with microparticulate vaccine delivery systems was investigated in this study. The microparticulates used were muramyl dipeptide (MDP) loaded ovalbumin microspheres (OVA-MSs) and fluorescent latex microspheres of fixed sizes of 2.3 and 2.1 microm diameter, respectively. Similar doses of OVA-MSs were injected subcutaneously (s.c.) and intradermally (i.d.) in mice. The induced OVA-specific IgG antibody immune response was found to be significantly higher in i.d. immunized mice as compared to those injected s.c. The sc and i.d. administration of fluorescent latex microspheres in mice demonstrated that the uptake and translocation of microspheres from the site of injection depends primarily upon the surface area of the microspheres. The enhancement in antibody production upon i.d. administration was explained on the basis of (i) an increased surface area of microspheres and a lower number of microspheres per injection site, and (ii) an increased probability of interaction with the immune cells of the skin. Efficient lymph node targeting observed from the id administered microspheres may be the result of both of these factors. The results of this study demonstrated that the intradermal route is an effective means of immunization for microparticulate vaccine delivery systems, requiring lower doses and resulting in a higher immune response as compared to the traditionally used sc route.

Determining the absolute surface hydrophobicity of microparticulates using thin layer wicking

Surface hydrophobicity is an important factor in the transport of microparticulates (MPs) across biological barriers. We have previously shown in our laboratory that the surface properties of polystyrene MPs influence the diffusion and transport through gastrointestinal (GI) mucus and mucin. Unfortunately, most currently used methods for evaluating the surface hydrophobicity of MPs involve a relative measurement resulting in a rank order rather than an absolute hydrophobicity value. Obtaining an absolute assessment of hydrophobicity is necessary in order to obtain meaningful comparisons and correlations across laboratories, polymers, methods of fabrication, and so on. A modified thin layer wicking (TLW) technique was developed and validated to allow for the determination of absolute surface hydrophobicity of intact MPs. The TLW method was validated by constructing a standard curve and comparing the rate of solvent rise through MPs dried on microscope slides to the known contact angle of PLGA polymers. MPs with surface contact angles ranging between 67.04 degrees and 90.18 degrees were evaluated using the TLW technique. The modified TLW technique was also successfully validated using surface-modified polystyrene and OVA MPs. Based on the results of the current study, the modified TLW technique appears to be a reliable and quantitative method for assessing the surface hydrophobicity of intact MPs.

Albumin nanospheres as carriers for passive drug targeting: an optimized manufacturing technique

PURPOSE

The purpose of this study was to develop a new method to produce albumin particles in the sub-200-nanometer range with a narrow size distribution and in a controlled and reproducible manner.

METHODS

A new emulsion crosslinking method was developed using ultrasound and static mixing as homogenization steps and a central composite design was used to evaluate the influence of different process parameters on particle size, polydispersity and yield.

RESULTS

Response surface analysis allowed the location of the most important factors. Of all the factors investigated, only the albumin concentration and the aqueous phase volume showed a significant influence on response parameters. Albumin nanospheres with sizes below 200 nm in diameter and very narrow size distributions were obtained in high yields ( > 80%).

CONCLUSIONS

This study describes a new preparation method for albumin nanoparticles which are suitable for future drug targeting studies.

Albumin microspheres as a drug delivery system: relation among turbidity ratio, degree of cross-linking, and drug release

The degree of cross-linking of albumin microspheres, with and without drug, was assessed using turbidity measurements carried out in the presence of water and the protein denaturant guanidine hydrochloride (GuHCl) at a concentration that disrupted noncovalent bonds while having no effect on covalent bonds. The measurements allowed calculation of a turbidity ratio (TG/TW), expressed as the ratio of the turbidity of albumin microspheres in 6 M GuHCl (TG) divided by that in water (TW). A linear relation existed between TG/TW and the (i) temperature at which the microspheres were prepared, (ii) concentration of the cross-linking agent glutaraldehyde, and (iii) time of exposure to a second cross-linking agent, formaldehyde vapor, three conditions that increase the degree of cross-linking. The turbidity ratio also increased as the concentration of the albumin solution used to prepare the microspheres increased from 25 to 50%. Drug release from the microspheres consisted of an initial, rapid, burst followed by a second, slower, phase. The rates in both release phases were inversely related to the turbidity ratio, suggesting that this parameter has utility as an indicator of the degree of cross-linking in albumin microspheres.

Microspheres of human serum albumin with barbiturates: effect of drug partition coefficient on preparation and drug release

Human serum albumin microspheres were prepared with a series of barbiturates by the thermal denaturation method. The barbiturates were of similar general physicochemical properties but different partition coefficients. The total drug content of microspheres was dependent on the partition coefficient, and an increase in the partition coefficient caused a decrease in the drug content of finished microspheres due to drug migration to the outer organic phase during preparation. The ensemble drug release from microspheres was followed by the paddle method and by potentiometric titration with a pH-stat. Nonlinear regression analysis showed the best fit for the spherical Higuchi equation, especially first-order kinetics (biphasic). The drug partition coefficient affected the release in such a way that drugs with higher partition coefficients were released faster and to a greater extent than those with lower coefficients.

Passive vectoring of a colloidal carrier system for sodium stibogluconate: preparation, characterization and performance evaluation

The intracellular residence of the Leishmania parasite in the cells of the reticuloendothelial system--predominantly the liver and spleen--prompted the development of a polymeric, particulate, colloidal carrier system for the antileishmanial drug sodium stibogluconate. The system was pharmaceutically characterized for shape, size, structural integrity, electrokinetic properties and in vitro drug release. The relationship between such physical parameters as size, electrophoretic mobility and surface charge and the effectiveness of the system is discussed. Subsequent in vivo studies in rats revealed that the carrier system successfully vectored the drug to the site of infection.

Laser balloon angioplasty: potential for reduction of the thrombogenicity of the injured arterial wall and for local application of bioprotective materials

Mitigation of adverse biologic reactivity after balloon angioplasty is necessary before the incidence of restenosis can be appreciably reduced. A brief review of experimental evidence supports the hypothesis that the thrombogenicity of the injured arterial wall can be reduced by a suitable level of thermal denaturation or cross-linking of thrombogenic proteins. In addition, the concept of local pharmacologic therapy, which can be provided with laser balloon angioplasty at the site of arterial injury, is introduced. Preliminary in vitro and in vivo data suggest that guide catheter-injected albumin-heparin conjugates fabricated as water-insoluble microspheres remain adherent to the injured luminal surface and deeper arterial layers after physical trapping by the inflated balloon and subsequent laser/thermal exposure. The combination of initially adequate luminal morphology, reduction of the thrombogenicity of the injured arterial wall and application of local pharmacologic therapy with laser balloon angioplasty may eventually prove helpful in reducing the incidence of restenosis.

Cyclophosphamide loaded albumin microspheres II. Release characteristics

The purpose of this investigation was to evaluate the release characteristics of cyclophosphamide (CP) from glutaraldehyde stabilized human serum albumin microspheres, and to study the effect of the extent of cross-linking, the amount of the stabilizing agent and the size of the microspheres on the in vitro release of CP. Microspheres were prepared by emulsion polymerization method using two different volumes (0.1 and 0.7 ml) of glutaraldehyde solution (25 per cent) and two different crosslinking durations (15 min and 1 h). The resulting mean particle size of the microspheres also varied between 2.5 microns and 3.7 microns. The total CP content in microspheres was analysed from the surface drug and the entrapped drug.

Albumin microspheres. I: Physico-chemical characteristics

Albumin microspheres are biodegradable particles which can be readily radiolabelled and synthesized in the size range of 1 to 200 microns. During the last 30 years extensive efforts have been made towards the design and development of this carrier for the purpose of diagnosis and drug delivery. This review presents a thorough discussion on the physico-chemical characteristics of albumin microspheres.

Effects of microencapsulated monosialoganglioside GM1 on cholinergic neurons

The preparation, physical characterization and effects of microcapsules containing the monosialoganglioside GM1 in an in vivo rat model are described herewith. Several preparations of microcapsules were obtained differing in physical and chemical properties. Human serum albumin (HSA) microcapsules with or without GM1 are spherical in shape, have a consistent particle size (8-10 microns in diameter) and are devoid of large pores. In agreement with our previous work, we now provide further evidence that GM1 can prevent shrinkage and the decrease of choline acetyltransferase activity in the nucleus basalis magnocellularis (NBM) of the rat following a unilateral cortical lesion. In the present study we examined the effect of microencapsulated GM1 in this in vivo rat model. Local application of HSA-microencapsulated GM1 (in doses comparable to those obtained by i.c.v. administration) onto the surface of the lesioned cortex prevents both the biochemical and morphological degenerative changes in the NBM of rats with unilateral devascularizing cortical lesions. The results from these studies show that microencapsulated GM1 can be applied successfully and a prolonged controlled release of this drug obtained, thus avoiding surgical implantation of a cannula.

Factorial design based optimization of the formulation of albumin microspheres containing adriamycin

The use of factorial design in the formulation of adriamycin-associated albumin microspheres, using the heat-stabilization technique, is illustrated. The effect of stabilization temperature, protein concentration and stabilization time on the entrapment and recovery of adriamycin in microspheres have been investigated using a 2 x 4 x 4 factorial design. The associated drug content in unwashed and four times washed microspheres was determined using HPLC. Maximum drug association and drug recovery were obtained from microspheres synthesised using 25 per cent w/v albumin solution and stabilized at 120 degrees C for 2.5 min. Under these conditions, the entrapped and total associated drug content of the microspheres was about 4 per cent and 12 per cent w/w respectively, and the drug recovery was about 75 per cent. The in vitro dissolution study carried out using dynamic dialysis revealed that the release of adriamycin from these particles follows a bi-phasic pattern. The results demonstrate that use of short stabilization time, low protein concentration and low stabilization temperature are required for the formulation of microspheres with high adriamycin content.

Microencapsulated monosialoganglioside GM1: physical properties and in vivo effects

The prevention of the decrease of choline acetyltransferase (ChAT) enzymatic activity was achieved by applying GM1 in an animal model for studying retrograde degenerations of cholinergic neurons. Devascularizing lesions of the rat cortex led to a significant decrease in activity of ChAT in the nucleus basalis magnocellularis (NBM), but this decrease was effectively prevented by GM1 administration either centrally or locally in a microencapsulated form. Compared with the relatively large dose of GM1 which has to be given when the drug is administered. i.p. microencapsulated GM1 applied locally and directly over the lesioned cortical surface seems to be effective in much lower doses.

Radioprotective activity of ethylcellulose microspheres containing WR 2721, after oral administration

Ethylcellulose microspheres containing WR 2721 were prepared by the emulsion-solvent evaporation technique. No significant loss or degradation of this phosphorothioate was noted during preparation. Oral administration of these microspheres to mice gave an important lowering of WR 2721 toxicity and an enhancement of its radioprotective activity with a D.R.F. of about 1.7-1.8 over 2-3 h. This action is explained by the protection of WR 2721 from acid hydrolysis and degradation in the gastro-intestinal tract. The adsorption of a fraction of WR 2721 onto the surface of microspheres constitutes an inconvenience. This study confirms the interest of such carriers for providing important sustained radioprotection after oral administration.

Albumin microspheres for intra-articular drug delivery: investigation of their retention in normal and arthritic knee joints of rabbits

The retention of 131I-labelled albumin microspheres and microsphere-entrapped [131I]rose bengal was investigated in normal and experimentally arthritic knee joints of rabbits. Albumin microspheres were cleared slowly from the joint cavity and no significant difference was observed between normal and inflamed joints. Entrapment of rose bengal within albumin microspheres was found to delay the clearance of the drug from the joint when compared with a solution of rose bengal. In addition, the retention time for entrapped rose bengal was dependent on the degree of inflammation present.