In vitro and in vivo evaluation of poly(methylidene malonate 2.1.2) microparticles behavior for oral administration

The brain tissue response to biodegradable poly(methylidene malonate 2.1.2)-based microspheres in the rat

The aim of this study was to follow the in vivo biodegradation as well as to appreciate the brain tissue response to poly(methylidene malonate 2.1.2) (PMM 2.1.2)-based microspheres implanted into the rat brain. Ninety-three adult Sprague-Dawley female rats were engaged in the study in which 54 underwent stereotactic implantation of blank gamma-sterilized PMM 2.1.2-based microspheres, prepared by an emulsion-extraction method. Twelve rats were implanted with the same 5-fluorouracil (5-FU)-loaded microspheres. Seventeen controls received the suspension medium alone (carboxymethylcellulose aqueous solution). The animals were sacrificed on post-operative days 1, 2, 8 and months 1, 2, 3, 6, 9, 12, 15 and 18. The brains were dissected, frozen, cut in a freezing microtome, and the slides were processed for immunohistological evaluation and scanning electron microscopy. During the first few days, the moderate inflammatory response to blank or loaded PMM 2.1.2 microspheres was largely a consequence of the mechanical trauma that occurs during surgery. The macrophagous-microglial reaction was similar to the one typically found following any damage in the CNS. There were also no differences in GFAP reactivity between the implanted animals and the controls. Blank microspheres began to degrade between 3 and 6 months, while 5-FU microspheres degraded between 8 days and 1 month. The polymer degradation generated in both cases a pronounced inflammatory and immunological reaction, leading to an important cell loss, a cerebral atrophy and to the death of several animals. PMM 2.1.2 was thus shown to be inadequate for intracerebral drug delivery.

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.

Polymeric particulates to improve oral bioavailability of peptide drugs

Oral administration remains the most convenient way of delivering drugs. Recent advances in biotechnology have produced highly potent new molecules such as peptides, proteins and nucleic acids. Due to their sensitivity to chemical and enzymatic hydrolysis as well as a poor cellular uptake, their oral bioavailability remains very low. Despite sophisticated new delivery systems, the development of a satisfactory oral formulation remains a challenge. Among the possible strategies to improve the absorption of drugs, micro- and nanoparticles represent an exciting approach to enhance the uptake and transport of orally administered molecules. Increasing attention has been paid to their potential use as carriers for peptide drugs for oral administration.

This article reviews the most common manufacturing methods for polymeric particles and the physiology of particle absorption from the gastrointestinal (GI) tract. In a second part, the use of polymeric particulate systems to improve the oral absorption of insulin is discussed.

Bioadhesive characterization of poly(methylidene malonate 2.12) microparticle on model extracellular matrix

The efficacy of a drug delivery system is predicated on its retention in the target tissue. Microparticle is one of the most popular and effective drug delivery configurations. Recently, it has been shown that the interaction between drug-loaded microparticles and tissues is related to the effectiveness of paclitaxel delivery to the bladder wall of mice for treating superficial bladder cancer. In this study, the adhesive interaction between poly(methylidene malonate 2.12) or PMM 2.1.2 microparticles and collagen, which serves as the model extracellular matrix for bladder wall, was probed with confocal reflectance interference contrast microscopy (C-RICM), single-particle compressive force measurement and contact mechanics theory. Young's modulus of single PMM 2.1.2 microparticle was determined as 1.56 +/- 0.25 x 10(4)N/m(2). For plain PMM 2.1.2 microparticle in water (pH 5.5), the degree of deformation (a/R) on collagen coated substrate decreased from 0.77 to 0.26 against the increase of mid-plane diameter from 2 to 18 microm. The adhesion energy of PMM 2.1.2 microparticle was determined from Maguis-JKR theory and remained at around 1.5 mJ/m(2) against the increase of particle diameter. At pH 4, the average degree of particle deformation and adhesion energy was increased by 11% and 32%, respectively, in comparison with that at pH 5.5. The loading of paclitaxel in PMM 2.1.2 microspheres enhanced the deformation and adhesion of microspheres at pH 5.5. It is hypothesized that the electrostatic repulsion between paclitaxel and collagen at pH 4 reduces the adhesion energy of PMM 2.1.2-paclitaxel microsphere. This study may offer insight for design of future microparticulate delivery systems by providing the experimental and theoretical tools to study the bioadhesive interaction between drug-loaded microparticles and model extracellular matrices.

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

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

Intravesical administration of poly(methylidene malonate 2.1.2) paclitaxel microspheres is a promising approach for intracavitary chemotherapy of superficial bladder cancer.

Surface-engineered nanoparticles for multiple ligand coupling

The design of surface-engineered nanoparticles for targeting to specific sites is a major challenge. To our knowledge, no study in the literature deals with ligand functionalization of biodegradable nanoparticles through biotin-avidin interactions. With the aim of conceiving small-sized nanoparticles which can be easily functionalized with a variety of ligands or mixtures thereof, biotinylated and PEGylated biotin-poly(ethylene glycol)-poly(epsilon-caprolactone) (B-PEG-PCL) copolymers were synthesized and used to prepare nanoparticles of around 100 nm. Avidin, followed by biotinylated wheat germ agglutinin as a model lectin, were coupled to their surface by taking advantage of the strong biotin-avidin complex formation. The cytotoxicity of the nanospheres towards Caco-2 cells in culture was negligible (more than 82% cell survival for nanoparticle concentrations up to 300 microg/well). The amount of radiolabeled poly(lactic acid) (PLA) or PEG-PLA nanoparticles associated with Caco-2 cells was only 0.7% and 1.5% of the amount added, respectively. This value was increased to 8.5% when a sufficient amount of lectin was bound to the PEG-PLA copolymer. After further studies, the biotin-PEG-coated nanoparticles could be helpful tools for studying the interaction between cells and functionalized nanoparticles with various surface characteristics (PEG layer density and thickness, ligand type and density).