Bioadhesive Microparticles Research Articles

A review on recent advantages and evaluation of microparticles and their applications

Microparticles are free spherical dust between 1 and 1000 microns made of synthetic, non-biodegradable, and non-biodegradable polymers. There are two types of microparticles: microcapsules and micro matrix. The main types of microparticles are magnetic microparticles, polymer microparticles, bio-adhesive microparticles, biodegradable polymer microparticles, synthetic polymer microparticles, floating microparticles, and radioactive microparticles. The advantage of microcarriers over nanoparticles is that they do not cross the 100 nm interstitium during lymphatic transport and therefore act locally. Toxic substances can be solidified in the form of micro-encapsulated and dried particles. Moreover, methods to characterize numerous physicochemical parameters like drug release, thermal properties, and particle size are introduced, along with new tests like in vitro leaching tests and floating tests.

Development of sodium carboxymethyl cellulose based polymeric microparticles for in situ hydrogel wound dressing formation

18β-glycyrrhetinic acid (Gly), a natural compound obtained from licorice, is known both for the anti-inflammatory and antioxidant activities and for this reason useful for wound treatment. Due to its poor solubility, Gly is not suitable for formulations used in conventional topical products such as gels, foams and creams. Polymeric bioadhesive microparticles (MP), loaded with Gly, were developed to be introduced in the wound bed and swell, once in contact with the exudate, to form a hydrogel in situ able to close the wound. The MP were prepared by spray drying method from the polymeric solution of polysaccharide sodium carboxymethyl cellulose (CMC) and copolymer Soluplus® (SL). Soluplus® introduction in MP composition, using a 3:1 ratio (CMC/SL wt./wt.), allowed to stabilize Gly in non-crystalline form, favoring the improvement of water solubility, and to obtain a spherical with rugged surface MP morphology. Ex vivo studies showed these MP maintain high swelling capability and are able to form in situ a hydrogel for wound repair. The controlled release of Gly from the hydrogel stimulates keratinocyte growth, potentially supporting the physiological healing processes.

CURCUMIN LOADED POLYMERIC MICROSPHERES FOR VAGINAL DELIVERY: FORMULATION DESIGN, IN VITRO EVALUATION, KINETICS AND STABILITY STUDIES

The main objective of this research is to evaluate a new approach for the preparation of bio adhesive microparticles and to design an innovative vaginal delivery system for curcumin which is able to enhance the drug anticancer activity. Curcumin encapsulated microspheres were prepared by solvent evaporation method. The microspheres were found to be discrete, spherical with free-flowing properties and evaluated for particle size analysis, shape (scanning electron microscopy), drug encapsulation efficiency, FTIR, DSC studies and in vitro release performance. The best selected microsphere formulation (F2, containing drug: polymer ratio 1:2) was incorporated into gels with a bio adhesive polymer. The microencapsulated vaginal gels were evaluated for pH, spreadability, extrudability, viscosity, in vitro drug release, drug release kinetics, bio adhesion test, accelerated stability of selected gel formulation. In vitro drug release rate for selected microencapsulated bio adhesive vaginal gel (FS3 gel, containing 1 % w/w of drug loaded microspheres and 0.6 % w/w of Carbopol 934) was found to sustain curcumin over 12h. The results were then compared statistically and obtained a satisfactory correlation. Thus, in conclusion preparation protocol of microencapsulated vaginal gel study may be adopted for a successful development of newer drug delivery system of other drugs for administration to vagina.

Formulation and Evaluation of Novel Spray-dried Alginate Microspheres as Pulmonary Delivery Systems of Rifampicin in Rats

Abstract: Background: Lung administration of anti-biotics in the dry powder form is promising for improved treatment efficiency for pulmonary infections, as it increases drug concentration at sites of infection while minimizing systemic side effects. For poorly soluble molecules like rifampicin, an anti-tubercular drug encapsulated in particulate system in presence of β-cyclodextrin may improve lung delivery. Materials and Methods: Present study was aimed to evaluate the pharmacokinetic parameters of rifampicin loaded alginate spraydried microparticles administered by pulmonary route. Novel spray-dried sodium alginate microspheres were formulated with β-cyclodextrin to form bioadhesive microparticles for sustained release of rifampicin. The particles without β-cyclodextrin and without drug were also prepared. Intratracheal instillation was adopted for lung delivery in comparison with oral delivery of pure drug. Results: Around 75% microspheres were in the respirable range, with satisfied aerodynamic characteristics. Aqueous solubility and skin permeation of rifampicin were increased significantly in presence of β-cyclodextrin. The in vitro antimycobacterial activity of the formulation showed enhanced activity in presence of β-cyclodextrin. The relative bioavailability of rifampicin alginate microspheres administered by pulmonary route was significantly higher when compared to that of oral route indicating the therapeutic potential of microspheres as a promising alternative to the presently available oral route. Conclusion: Along with sustained release of drug from the particulate formulation, the presence of cyclodextrin has the potential to achieve higher therapeutic efficacy by increasing the solubility and permeation of rifampicin. Key words: Alginate, Aerodymanic Characteristics, β-cyclodextrin, Intratracheal instillation, Pulmonary drug delivery, Spray-dried microspheres.

Preparation and characterization of glycoprotein-resistant starch complex as a coating material for oral bioadhesive microparticles for colon-targeted polypeptide delivery.

For effective oral delivery of polypeptide or protein and enhancement their oral bioavailability, a new resistant starch-glycoprotein complex bioadhesive carrier and an oral colon-targeted bioadhesive delivery microparticle system were developed. A glycoprotein, concanavalin A (Con A), was successfully conjugated to the molecules of resistant starch acetate (RSA), leading to the formation of resistant starch-glycoprotein complex. This Con A-conjugated RSA film as a coating material showed an excellent controlled-release property. In streptozotocin (STZ)-induced type II diabetic rats, the insulin-loaded microparticles coated with this Con A-conjugated RSA film exhibited good hypoglycemic response for keeping the plasma glucose level within the normal range for totally 44-52 h after oral administration with different insulin dosages. Oral glucose tolerance tests indicated that successive oral administration of these colon-targeted bioadhesive microparticles with insulin at a level of 50 IU/kg could achieve a hypoglycemic effect similar to that by injection of insulin at 35 IU/kg. Therefore, the potential of this new Con A-conjugated RSA film-coated microparticle system has been demonstrated to be capable of improving the oral bioavailability of bioactive proteins and peptides.

Preparation and characterization of bioadhesive microparticles comprised of low degree of quaternization trimethylated chitosan for nasal administration: effect of concentration and molecular weight.

Toward the development of microparticulate carriers for nasal administration, N-trimethylchitosan chloride (TMC) of low molecular weight (LMW) and high molecular weight (HMW) and low degree of quaternization (16% and 27%, respectively) was co-formulated into microparticles comprising of dipalmatoylphosphatidylcholine (DPPC) and poly(lactic-co-glycolic) acid (PLGA) via the spray-drying technique. The chitosan derivatives were characterized by means of nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and Fourier transfrom infrared (FTIR) spectroscopy. The size and morphology of the produced microparticles were assessed by scanning electron microscopy (SEM), whereas their mucoadhesive properties were investigated by means of atomic force microscopy-force spectroscopy (AFM-FS). The results showed that microparticles exhibit mucoadhesion when TMC is present on their surface above a threshold of TMC (>0.3% w/w).

Improvement of an encapsulation process for the preparation of pro- and prebiotics-loaded bioadhesive microparticles by using experimental design

The purpose of this study was to design a new vaginal bioadhesive delivery system based on pectinate–hyaluronic acid microparticles for probiotics and prebiotics encapsulation. Probiotic strains and prebiotic were selected for their abilities to restore vaginal ecosystem. Microparticles were produced by emulsification/gelation method using calcium as cross-linking agent. In the first step, preliminary experiments were conducted to study the influence of the main formulation and process parameters on the size distribution of unloaded microparticles. Rheological measurements were also performed to investigate the bioadhesive properties of the gels used to obtain the final microparticles. Afterwards an experimental design was performed to determine the operating conditions suitable to obtain bioadhesive microparticles containing probiotics and prebiotics. Experimental design allowed us to define two important parameters during the microencapsulation process: the stirring rate during the emulsification step and the pectin concentration. The final microparticles had a mean diameter of 137 μm and allowed a complete release of probiotic strains after 16 h in a simulated vaginal fluid at +37 °C.

MR imaging of biodegradable polymeric microparticles: A potential method of monitoring local drug delivery

Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) was encapsulated into biodegradable, bioadhesive polymeric microparticles to enable noninvasive monitoring of their local intravesical delivery with MRI. The microparticles were characterized by contrast agent encapsulation and release kinetics, T(1) relaxation rates, and contrast enhancement in vivo. The level of Gd-DTPA loading into microparticles was 14.3 +/- 0.6 mug/mg polymer. The measured T(1) relaxation rates of the microparticles showed a direct dependence on Gd-DPTA content. Both 1.5T and 4.7T MR scanners were used to image murine bladders instilled intravesically with Gd-DTPA-loaded particles in vivo. MR images showed ring-shaped regions of enhancement inscribing the bladder wall, which were attributed to the microparticles that were preferentially adherent to the mucosa lining the urothelium. The images of controls exhibited no such enhancement. The normalized signal intensities measured from post-instillation images were significantly greater (P < 0.05) than those in the pre-instillation images. Contrast enhancement was observed for at least 5 days after the initial instillation, although the enhancement decreased due to microparticle degradation or mucosa renewal. The localized distribution of biodegradable, bioadhesive microparticles encapsulating Gd-DTPA was successfully visualized with MRI in vivo, allowing particle-mediated delivery to be temporally and spatially monitored noninvasively.

Efficacy of Paclitaxel Released From Bio-Adhesive Polymer Microspheres on Model Superficial Bladder Cancer

We aimed to promote the efficacy of paclitaxel in intracavitary treatment of superficial transitional cell carcinoma of the bladder by designing bio-adhesive microspheres capable of achieving controlled release of the drug at the urothelium/urine interface. Poly(methylidene malonate 2.1.2) microspheres encapsulating paclitaxel were prepared by a single emulsion method. Bioactivity of the released paclitaxel was confirmed by assessing cytotoxicity on MBT-2, a bladder cancer cell line. Biodistribution of particles after bladder instillation was assessed by confocal microscopy and scanning electron microscopy. In vivo studies were performed in Balb/c mice after bladder cancer was induced by BBN (N-n-Butyl-N-butan-4-ol-nitrosamine) in drinking water. The efficacy of intravesical injections of conventional and microsphere paclitaxel was assessed by histology and survival rates. Spherical 5 microm microspheres with 5% weight per weight paclitaxel loading ensured sustained release of bioactive paclitaxel. After bladder instillation the microspheres adhered to the mucosa and remained in the bladder lumen for at least 48 hours. In the BBN induced bladder cancer model compared with controls the 9-week survival rate was significantly improved by 2 injections of paclitaxel bio-adhesive microparticles. Microscopic evaluation confirmed the lower incidence of carcinoma in situ and high grade transitional cell carcinoma after injections of paclitaxel bio-adhesive microparticles compared with controls and with injections of similar doses of the conventional paclitaxel formulation. Intravesical administration of poly(methylidene malonate 2.1.2) paclitaxel microspheres is a promising approach for intracavitary chemotherapy of superficial bladder cancer.

Bioadhesion: new possibilities for drug administration?

Bioadhesion (and mucoadhesion) is the process whereby synthetic and natural macromolecules adhere to mucosal surfaces in the body. If these materials are then incorporated into pharmaceutical formulations, drug absorption by mucosal cells may be enhanced or the drug released at the site for an extended period of time. For synthetic polymers, such as the chitosans, carbopols and carbomers, the mechanism of bio/mucoadhesion is the result of a number of different physicochemical interactions. Biological bio/mucoadhesives, such as plant lectins, show specific interactions with cell surfaces and mucin and are seen as the 'second generation' bioadhesives. Bioadhesive systems for drug administration via the buccal and nasal cavities are nearing the market; in the case of nasal bioadhesion, bioadhesive microparticles are used. A bioadhesive formulation for drug administration to the vagina is in use. The gastrointestinal tract is proving a more difficult site because of the rapid turnover of mucus, and relatively constant transit time, but intensive research is in progress. Micro- and nano-particles, coated with either bio/mucoadhesive polymers or specific biological bioadhesives, are showing some promise, but will require considerable research and development before reaching the market.

Induction of secretory immunity with bioadhesive poly (D,L-lactide-co-glycolide) microparticles containing Streptococcus sobrinus glucosyltransferase.

The effect of mucosal delivery of Streptococcus sobrinus glucosyltransferase (GTF) in bioadhesive poly (D,L-lactide-co-glycolide) (PLGA) microparticles on induction of salivary IgA and serum IgG antibody responses was measured in Sprague-Dawley rats. Preparations of GTF/PLGA/gelatin microparticles, or PLGA/gelatin microparticles or GTF in alum, were administered four times at weekly intervals by intranasal or intragastric routes. Two subcutaneous injections of GTF in PLGA/gelatin microparticles or in alum were given to separate groups of rats. Significant elevations in salivary IgA antibody levels to S. sobrinus GTF were observed only in the groups immunized intranasally 28 days after immunizations were begun. Five of six rats given the GTF microparticles intranasally had positive salivary IgA antibody responses to GTF, and the mean salivary IgA antibody level of this group was 30-fold higher than any other mucosally or systemically immunized group. Salivary IgA responses in the GTF-microparticle group remained significantly higher than all other mucosally immunized groups for at least 10 weeks after the primary immunization. All rats in this group demonstrated aspects of anamnesis following a more limited secondary course of intranasal administration. Intranasal administration of GTF in microparticles also induced a serum IgG response to GTF in some rats. After secondary intranasal GTF microparticle administration, several rats had sustained serum IgG antibody levels that were within the range of sera from rats subcutaneously injected with GTF in microparticles or in alum. Thus intranasal delivery of GTF-containing bioadhesive microparticles induced the highest and longest lasting salivary immune response of any mucosal or systemic route or vehicle tested and could be expected to be a useful method for induction of mucosal immunity.

Microencapsulated fluorinated gases for use as imaging agents

It has been discovered that the incorporation of fluorinated gases, especially a perfluorocarbon such as octafluoropropane, into synthetic polymeric microparticles, significantly enhances echogenicity as compared with microparticles having air incorporated therein. The microencapsulated perfluorocarbon is manufactured with a diameter suitable for the targeted tissue to be imaged, for example, for intravenous or oral administration. In one embodiment, bioadhesive microparticles are formed for enhanced imaging of mucosal surfaces.