Cytotoxicity of 5-fluorouracil entrapped in gelatin microspheres

Gelatin microspheres were prepared by water/oil emulsion polymerization and by cross-linking with glutaraldehyde. For the microsphere preparation procedure, two different gelatin (5 or 10% w/v) and three different glutaraldehyde (5, 0.5 or 0.1% v/v) concentrations were used. The influence of preparation compositions on microsphere recovery, particle size and morphology, swelling and degradation, 5-fluorouracil loading and release, and cytotoxicity were investigated. The concentrations of gelatin and glutaraldehyde influenced the size and surface properties of microspheres. The decrease in gelatin concentration and the increase in glutaraldehyde concentration resulted in the formation of smaller (140.82-71.47 microm for gelatin microspheres with a 5% gelatin content; 297.67-97.44 microm for gelatin microspheres with a 10% gelatin content) microspheres with smoother surface properties. Swelling values were decreased as the amount of glutaraldehyde was increased. In particular, for microspheres with a high glutaraldehyde content (5% v/v), only about 15% were degraded in 12 days, whereas for those with 0.5% (v/v) glutaraldehyde, almost 97% degradation occurred in the same period. The most rapid 5-fluorouracil release was observed from uncross-linked microspheres (about 88% in 4 h), whereas a particular slower release (about 36% in 4 h) profile was obtained for the highly cross-linked ones. Cytotoxicity tests of free and entrapped 5-fluorouracil were carried out with MCF-7 breast cancer cell line. Free 5-fluorouracil produced an immediate effect, whereas entrapped 5-fluorouracil showed a prolonged cytotoxic effect.     

In situ lyophilisation of nifedipine directly in hard gelatine capsules

Hydrophobic drugs present a challenge due to: (i) adhesion and agglomeration; hence the choice of the suitable processing technique to have the drugs into orally administered dosage forms is critical. (ii) Poor dissolution and poor aqueous solubility; hence poor bioavailability. A novel method which is in situ lyophilisation directly in hard gelatin capsule shells was used in this research to enhance the dissolution of nifedipine (a model hydrophobic drug) in the presence of co-povidone, Pluronic^®F-127 and inulin as enhancement excipients (to the best of our knowledge those excipients have not been previously used with nifedipine in lyophilised forms).

Solutions of nifedipine and excipients in a range of concentrations (0.5, 1, 5 and 10%w/v) were prepared using a co-solvent system of tert- butyl alcohol/water mixture. These solutions were filled directly into bodies of size 000 hard gelatin capsule shells and freeze dried. Pure drug and all formulations were characterised by solubility, wetting studies and in vitro dissolution. Also, conformational integrity and thermal characteristics of nifedipine formulations were investigated using FT-IR spectroscopy and differential scanning calorimetry (DSC), respectively. The in situ lyophilisation of nifedipine with excipients, looks a promising method not only to improve the hydrophobic drug dissolution but also to be cost effective.     

Optimization of controlled drug release through interfacial polymerization

Interfacial nylon polymerization was chosen from the different in situ polymerization techniques to assess its utilization for controlled release medication. Sulfadiazine sodium was selected for such investigation, and several polymerization factors were altered during the technique stated. The pharmaceutical properties of the resulting products were used to evaluate the factor under consideration. The total product yield, as well as the product flowability were decidedly superior in the presence of either cross-linked gelatin or calcium alginate as aqueous phase modifiers during polymerization. Particle size was shown to increase depending upon the type and concentration of the included modifier. Scanning electron micrographs have confirmed morphologically the porous nature of the polymer coat. The latter displayed some pronounced effects on the first-order medicament dissolution kinetics.     

Effect of process variables on particle size of gelatin microspheres containing lactic acid

Gelatin microspheres containing lactic acid were prepared by a polymerization technique using glutaraldehyde as the cross-linking agent. Because particle size distribution of microspheres is a vital factor in the characterization of microspheres, the present study was carried out to evaluate the effect of process variables on the microspheres size distribution. It was found that concentration of a gelatin solution is the most important parameter that influences the particle size of microspheres. By using different concentrations of gelatin solution, microspheres with different size ranges were prepared. Both the stirring rate of the system and the volume ratio of aqueous and oil phases exerted a great influence on microsphere-size distribution, whereas, cross-linking time and cross-linker concentration only affected the yield. Lower-phase volume ratios resulted in small uniform microspheres with smooth surfaces and a narrow size range. The effect of emulsifier concentration (span 80), below 1% (w/w, with respect to the weight of the oil phase), on particle size was appreciable. However, at higher concentrations, little effect was observed.     

Solubility of drugs in the presence of gelatin: effect of drug lipophilicity and degree of ionization

The solubility of seven drugs (nitrofurantoin, chlorothiazide, phenobarbital, prednisolone, griseofulvin, diazepam and piroxicam) in the absence and presence of gelatin was measured, at three different pH values (3.7, 5.0 and 7.0) at 37 degrees C. Drugs studied had different physicochemical properties (log P, pK(a), aqueous solubility) and their solubility in presence of 0.1 and 0.5% (w/v) hydrolyzed (and in some cases common) gelatin was estimated. Results show that the solubility of all drugs is significantly enhanced, especially in the presence of 0.5% gelatin. This gelatin-induced enhancement in drug solubility is higher in the pH in which acidic drugs are less ionized, especially for the less lipophilic acidic drugs (nitrofurantoin, chlorothiazide). In all cases, drug solubility in presence of gelatin is correlated with their aqueous solubility. Therefore, the established relationships between aqueous and gelatin solubility can be employed to derive an estimate of the drug solubility in presence of gelatin once its aqueous solubility is known. With the exception of piroxicam which is highly ionized and phenobarbital which is relatively soluble, there seems to be a tendency for larger gelatin-induced increases in solubility as drug lipophilicity increases or aqueous solubility decreases.     

Effect of Process Variables on Particle Size of Gelatin Microspheres Containing Lactic Acid

Gelatin microspheres containing lactic acid were prepared by a polymerization technique using glutaraldehyde as the cross‐linking agent. Because particle size distribution of microspheres is a vital factor in the characterization of microspheres, the present study was carried out to evaluate the effect of process variables on the microspheres size distribution. It was found that concentration of a gelatin solution is the most important parameter that influences the particle size of microspheres. By using different concentrations of gelatin solution, microspheres with different size ranges were prepared. Both the stirring rate of the system and the volume ratio of aqueous and oil phases exerted a great influence on microsphere‐size distribution, whereas, cross‐linking time and cross‐linker concentration only affected the yield. Lower‐phase volume ratios resulted in small uniform microspheres with smooth surfaces and a narrow size range. The effect of emulsifier concentration (span 80), below 1% (w/w, with respect to the weight of the oil phase), on particle size was appreciable. However, at higher concentrations, little effect was observed.     

Studies on solubility and hypoglycemic activity of gliclazide beta-cyclodextrin-hydroxypropylmethylcellulose complexes

This study was undertaken with an objective to increase the dissolution rate and bioavailability of a poorly water soluble drug gliclazide (Gz) by complexation with beta-cyclodextrin (CD) in the presence of hydroxypropylmethylcellulose (HPMC). Phase solubility studies of Gz were performed in aqueous solutions of different concentrations of CD alone and in the presence of some water soluble polymers. Gz-CD complexes were prepared in 1:1 and 1:2 drug:CD molar ratios by autoclaving, neutralization and kneading methods. The complexes were also prepared in the presence of 0.05% w/w HPMC. Physical mixtures of Gz-CD in 1:1 and 1:2 molar ratios were also prepared. Complexes and physical mixtures were characterized and evaluated for in vitro dissolution in distilled water and hypoglycemic activity in rats. CD enhanced the dissolution of Gz to 1.5 to 2.0 fold. Presence of water soluble polymer HPMC in Gz-CD complexes further enhanced the rate and extent of drug dissolution to 2.5 fold. Gz-CD-HPMC complexes were found to be more promising as they produced not only an early onset but also more intense hypoglycemic effect as compared to pure drug powder and commercial tablets.     

Preparation of gelatin microspheres containing lactic acid--effect of cross-linking on drug release

In this study, gelatin microspheres containing lactic acid were prepared by the polymerization technique using glutaraldehyde as the cross-linking agent. Dried microspheres were loaded by immersing them in an aqueous solution of lactic acid. In order to prepare microspheres with an appropriate drug release profile, the effect of time of cross-linking and the amount of cross-linking agent on the swelling properties of microspheres and their release profile were investigated. The microencapsulation efficiency, microspheres appearance, particle size, swelling ratio and drug release profile were also studied. Microspheres prepared with a larger amount of cross-linking agent, or after longer cross-linking time, showed a reduced swelling ratio in aqueous media. In vitro release pattern of lactic acid from gelatin microspheres showed a biphasic profile and the release rates were reduced upon increasing the amount of cross-liking agent and prolonging the cross-linking time.     

Effect of process variables on particle size and viability of Bifidobacterium lactis Bb-12 in genipin-gelatin microspheres

Gelatin microspheres cross-linked with genipin were developed to encapsulate the probiotic Bifidobacterium lactis Bb-12 The effects of different gelatin concentrations (10-19% w/v), bloom strengths (175 and 300), surfactants, stirring rates during emulsion formation and genipin concentrations (0-10 mM) on the microsphere sizes and viability of bacterial cells were investigated. Principal Component Analysis revealed microsphere size distribution differed depending on the presence or absence of surfactants as well as a trend of increasing micropshere size with increasing gelatin concentration and bloom strength. Lower stirring rates resulted in larger microspheres with higher encapsulation yields of bifidobacteria Microsphere size and cell viability were not significantly (p < 0.05) influenced by increasing genipin concentrations up to 10 mM whereas microsphere stability in simulated gastric juice increased with increasing genipin concentration. The encapsulation yields were higher in 175 bloom strength gelatin microspheres than in 300. Cold-stage scanning electron microscopy showed encapsulated bacteria distributed throughout the genipin cross-linked gelatin matrix.     

Effect of process variables on particle size and viability of Bifidobacterium lactis Bb-12 in genipin-gelatin microspheres

Gelatin microspheres cross-linked with genipin were developed to encapsulate the probiotic Bifidobacterium lactis Bb-12 The effects of different gelatin concentrations (10–19% w/v), bloom strengths (175 and 300), surfactants, stirring rates during emulsion formation and genipin concentrations (0–10?mM) on the microsphere sizes and viability of bacterial cells were investigated. Principal Component Analysis revealed microsphere size distribution differed depending on the presence or absence of surfactants as well as a trend of increasing micropshere size with increasing gelatin concentration and bloom strength. Lower stirring rates resulted in larger microspheres with higher encapsulation yields of bifidobacteria Microsphere size and cell viability were not significantly (p?<?0.05) influenced by increasing genipin concentrations up to 10?mM whereas microsphere stability in simulated gastric juice increased with increasing genipin concentration. The encapsulation yields were higher in 175 bloom strength gelatin microspheres than in 300. Cold-stage scanning electron microscopy showed encapsulated bacteria distributed throughout the genipin cross-linked gelatin matrix.     

The effect of gelatin grade and concentration on the migration of solutes into and through glycerogelatin gels

The diffusion of 4-hydroxybenzoic acid and phenobarbitone through glycerogelatin gels was found to be independent of the type of gelatin used. Three types of gelatin, two acid-processed and one alkali-processed were studied, and the bulk viscosities of gels prepared from them was seen to vary considerably. However, the microviscosities of the gels, as measured by ESR, showed no significant differences. Thus microviscosity was the factor governing diffusion. Gelatin concentration in aqueous solutions without glycerol influenced microviscosity and hence diffusion. This is believed to be caused by dissolution of water-soluble fractions of the gelatin. Interstices in the gelatin matrix, though reduced in size when gelatin concentration is raised, are still too large to act as physical barriers to diffusing molecules. It is suggested that hydrated gelatin forms the matrix of glycerogelatin mixtures and that the interstitial fluid, through which migration occurs, consists almost entirely of glycerol and water.     

Cross-linking of hard gelatin carbamazepine capsules: effect of dissolution conditions on in vitro drug release.

The aim of this study was to determine if the use of both enzyme and surfactant in the dissolution medium changes the in vitro drug release from cross-linked hard gelatin capsules containing a water-insoluble drug. Hard gelatin capsules were cross-linked by a controlled exposure to formaldehyde resulting in different stressed capsules and carbamazepine (CBZ) was chosen as a drug model. In vitro dissolution studies were conducted using simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) with enzymes. Sodium lauryl sulfate (SLS) was added in the dissolution medium at a concentration of 2% m/v both in SGF and SIF with pepsin and pancreatin, respectively. The percentage of CBZ dissolved was reduced by increasing the degree of gelatin cross-linking. For unstressed hard gelatin capsules, 36% of the CBZ was released after 1 h, lowering to 5% for highly stressed hard gelatin capsules in the SGF. A similar effect was observed with SIF. In the case of moderately stressed hard gelatin capsules, addition of enzyme in the dissolution medium enhanced the percentage of CBZ dissolved. The dissolution level increased from 12% to 39% in SGF with pepsin for hard gelatin capsules cross-linked with 1500 ppm formaldehyde. On the contrary, the use of enzyme in the dissolution medium did not increase the dissolution of CBZ from highly stressed hard gelatin capsules. Surprisingly, the addition of SLS in the medium did not allow the release of the CBZ both in SGF and in SIF. The results of this study demonstrate that the use of enzyme in the dissolution medium is justified for moderately cross-linked hard gelatin capsules. However, the action of a surfactant added in the medium containing enzyme remains unclear.     

Preparation and detection of calcium alginate/bone powder hybrid microbeads for in vitro culture of ADSCs

Abstract

Calcium alginate microbeads have been widely used in tissue engineering application, due to their excellent biocompatibility, biodegradability, enhanced mechanical strength and toughness. Bone powder containing abundant hydroxylapatite, type I collagen and growth factors such as BMP2 and BMP4, possesses good osteoinductive activity. Herein, a hybrid calcium alginate/bone powder microbead was therefore prepared. Afterwards, different seeding density of adipose-derived stem cells (ADSCs) in these hybrid microbeads was discussed systematically for further in vitro expansion. Optimised microbeads suitable for in vitro expansion and differentiation of ADSCs were prepared using the droplet method under overall considering suitable concentrations of calcium alginate and calcium chloride as well as the density of bone powder through an orthogonal experiment. The results showed that the concentration of sodium alginate had the most influence on inside mass transfer and mechanical strength of the hybrid microbeads, secondly the calcium chloride, then the density of bone powder. The hybrid microbeads could be optimally performed while the concentrations of sodium alginate and calcium chloride were 2.5% and 4.5%, as well as 5.0?mg/mL bone powder, respectively. Live/Dead assay showed that the expanded ADSCs differentiated well with an initial embedding density of 5?×?10⁶ cells/mL.     

Gelatin microspheres crosslinked with D,L-glyceraldehyde as a potential drug delivery system: preparation, characterisation, in vitro and in vivo studies

To overcome the restriction in using crosslinked gelatin in the pharmaceutical field, D,L-glyceraldehyde (GAL), a non-toxic crosslinking agent, was proposed. Gelatin microspheres crosslinked with different concentrations of GAL (0.5, 1 or 2%, w/v) and for different time periods (1 or 24 h) were prepared. The effect of the preparation variables was evaluated analysing the extent of crosslinking, the morphological aspect, the particle size and the swelling behaviour. To evaluate the pharmaceutical properties, an antihypertensive drug, clonidine hydrochloride, was chosen as drug model and loaded into the microspheres. Either the increase of the crosslinker concentration or of the crosslinking time period decreased both the swelling and the in vitro drug release processes of the microspheres. After the subcutaneous injection, the loaded microspheres crosslinked with the lowest GAL concentration (0.5%, w/v) or for the shortest time period (1 h) showed a reduction of systolic blood pressure (SBP) similar to that recorded with a clonidine hydrochloride solution having the same drug concentration. Instead, the microspheres crosslinked for 24 h with concentrations of GAL higher than 0.5% (w/v) produced a more gradual and sustained SBP reduction and the antihypertensive effect was maintained until 52-72 h. The biocompatibility studies showed that the microspheres crosslinked with GAL are well tolerated in vivo. These results suggest the potential application of gelatin microspheres crosslinked with GAL as a suitable drug delivery system for the subcutaneous administration.     

In vitro and in vivo evaluation of a fast-disintegrating lyophilized dry emulsion tablet containing griseofulvin.

Development of a fast-disintegrating lyophilized dry emulsion (LDE) tablet that enhanced the in vitro dissolution and in vivo absorption of griseofulvin (GF) is presented. The LDE tablets were prepared by freeze-drying o/w emulsions of GF, a drug for which bioavailability is known to be enhanced by fat co-administration. Oil-in-water emulsions were prepared using a gelatin solution (2%, w/v) as the water phase and medium chain triglycerides (Miglyol) or sesame oil as the oil phase. In addition, different emulsifiers were evaluated. The influence of formulation parameters on the disintegration and in vitro dissolution of GF from LDE tablets along with other tablet characteristics were investigated. A significant influence of the emulsifier type on the tablet disintegration time was seen (p<0.01). Results obtained from dissolution studies showed that LDE tablets of GF improved the dissolution rate of the drug compared to the plain drug. The extent of absorption of GF from a selected LDE tablet formulation as compared to an immediate release conventional tablet as reference after single oral dose (125mg) administration was determined in four healthy subjects using a randomized crossover design. In this study, the rate of absorption of GF from LDE tablet was faster than that from the reference tablet and had significantly higher (p=0.02) peak plasma concentration (more than three times higher) and shortened time to C(max) by 4h (p=0.014). The extent of absorption expressed by AUC was 85% larger as compared to the commercial tablet. Stability results, after 6 months storage of LDE tablets at 25 degrees C and 60% relative humidity, showed a slight increase in disintegration time and residual moisture content, while results from dissolution studies showed slightly slower initial drug release.     

Effect of magnesium carbonate on the solubility,dissolution and oral bioavailability of fenofibric acid powder as an alkalising solubilizer

To investigate the possibility of developing a novel oral pharmaceutical product using fenofibric acid instead of choline fenofibrate, the powder properties, solubility, dissolution and pharmacokinetics in rats of fenofibrate, choline fenofibrate and fenofibric acid were compared. Furthermore, the effect of magnesium carbonate, an alkalising agent on the solubility, dissolution and oral bioavailability of fenofibric acid was assessed, a mixture of fenofibric acid and magnesium carbonate being prepared by simple blending at a weight ratio of 2/1. The three fenofibrate derivatives showed different particle sizes and melting points with similar crystalline shape. Fenofibric acid had a significantly higher aqueous solubility and dissolution than fenofibrate, but significantly lower solubility and dissolution than choline fenofibrate. However, the fenofibric acid/magnesium carbonate mixture greatly improved the solubility and dissolution of fenofibric acid with an enhancement to levels similar with those for choline fenofibrate. Fenofibric acid gave lower plasma concentrations, AUC and C_max values compared to choline fenofibrate in rats. However, the mixture resulted in plasma concentrations, AUC and C_max values levels not significantly different from those for choline fenofibrate. Specifically, magnesium carbonate increased the aqueous solubility, dissolution and bioavailability of fenofibric acid by about 7.5-, 4- and 1.6-fold, respectively. Thus, the mixture of fenofibric acid and magnesium carbonate at the weight ratio of 2/1 might be a candidate for an oral pharmaceutical product with improved oral bioavailability.     

Rapidly absorbed solid oral formulations of ibuprofen using water-soluble gelatin

Rapidly absorbed oral dosage forms of ibuprofen using water-soluble gelatin (hydrolysate of common gelatin: mean mol. wt: 6000) have been studied and compared with tablets prepared with common gelatin (mean mol. wt: 100,000) and commercial tablets. Spray-dried and speed-kneaded powders, two types of granules and tablets were prepared with water-soluble gelatin. The in-vitro dissolution rates of water-soluble gelatin preparations were significantly faster than those of commercial tablets, whereas the tablets prepared using common gelatin had slower dissolution rates than commercial tablets. Water-soluble gelatin enhanced the dissolution rate of ibuprofen by improving the wettability of the drug particle surface by water, without any interaction in solution and the solid state. The absorption behaviour of various preparations was evaluated in four beagle dogs. The peak concentration time (tmax) of the water-soluble gelatin preparations was significantly shorter than that of tablets prepared with common gelatin and commercial tablets. The maximum concentration (cmax) and the area under the serum concentration-time curve (AUCo-10 h) were similar in all cases. The serum concentration profiles of water-soluble gelatin solid preparations were almost the same as those of the solutions. On the other hand, the profiles of the common gelatin tablets were similar to those of the commercial tablets. The mean absorption time (MAT) from water-soluble gelatin preparations was about 0.7 h, while the MAT from commercial tablets and common gelatin tablets was about 1.2 h. The differences in the MAT of water-soluble gelatin preparations and commercial tablets or common gelatin tablets were the same as the differences in mean dissolution time (MDT) in gastrointestinal fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of soft gelatin on digoxin absorption.

1 The influence of encapsulation in soft gelatin on the absorption of digoxin from a solvent mixture of polyethylene glycol 400 90% W/W, ethanol 6% W/W, propylene glycol 3% W/W and water 1% W/W was studied in eight healthy volunteers. 2 Each volunteer received 0.6 mg digoxin as solution alone, as three intact capsules containing digoxin solution, as three capsules containing digoxin solution sectioned in half and as three capsules containing digoxin solution dissolved in water prior to administration. 3 There was no significant difference between the four treatments in terms of area under the plasma concentration--time curves for 7 h, peak plasma concentrations, time to peak or in the cumulative urinary excretion for 6 days. 4 It is suggested that a constituent of the solvent rather than the presence of or encapsulation within soft gelatin may be the determining factor in enhanced absorption of digoxin from soft gelatin capsules as compared to aqueous solution or tablets of rapid dissolution rate.     

Examination of self-crosslinked gelatin as a hydrogel for controlled release.

A gelatin matrix crosslinked by extensive dehydration was examined for use in controlled drug delivery in this preliminary investigation. Crosslinking is necessary to prevent gelatin dissolution and immediate drug release at body temperature. Treatment at 105 degrees C and reduced pressure induced crosslinking in discs prepared from Type B gelatin. Crosslinking was evaluated by determining changes in gelatin solubility at 37 degrees C in a USP paddle dissolution apparatus. The crosslinking treatment was reproducible and resulted in 90% of the original gelatin mass remaining after 12 h in water and in phosphate buffer solutions of pH 3 and 6.4. The treated gelatin discs remained intact for greater than 24 h at pH 6.4. Chlorpromazine.HCl (CPZ) was incorporated as a model drug by soaking the treated gelatin discs in an aqueous solution of the drug. Release of CPZ at 37 degrees C in the dissolution apparatus was fitted to an empirical equation. A coefficient of this equation was used as the initial release rate for comparison between different release profiles. The roles of drug solubility, matrix swelling and erosion, and potential drug-matrix interactions were examined by conducting release studies at pH values of 3, 4, 6.4, and 7.4. The insoluble, un-ionized form of the drug had the slowest release rate. The soluble, ionized form under conditions of maximum swelling and a possible drug-matrix repulsive interaction had the fastest release rate. General electrostatic drug-matrix interactions were noted which could influence the drug release rate depending on conditions of the study. The times for 50% release of CPZ ranged from 1.8 to 11.3 h.     

The influence of polymorphism on the manufacturability and in vitro dissolution of sulindac-containing hard gelatin capsules

Abstract

Context: Drug polymorphism could affect drug product dissolution, manufacturability, stability and bioavailability/bioequivalence. The impact of polymorphism on the manufacturability and in vitro dissolution profiles of sulindac capsules has not been studied yet.

Objective: To evaluate the impact of polymorphism on the manufacturability and in vitro dissolution of sulindac hard gelatin capsules.

Materials and methods: Sulindac crystal forms I and II (SLDI and SLDII, respectively) were prepared and characterized. Powder formulations containing one of the polymorphs, lactose and magnesium stearate (at three different levels) were prepared and their flow properties determined. Hard gelatin capsules were filled with the formulations and tested for fill-weight variations. Drug dissolution for SLDI- and SLDII-containing hard gelatin capsules was determined.

Results: Differences in flow properties for each polymorph were observed, as well as for their formulations, which in turn affected capsule weight homogeneity. Statistically significant differences in the rate and extent of drug release were observed between SLDI- and SLDII-containing capsules.

Discussion: Formulations containing SLDI showed a better manufacturability and a better dissolution profile than those with SLDII.

Conclusion: Sulindac crystalline form I was the best candidate for hard gelatin capsule formulation because of its technological and in vitro dissolution properties.