Methotrexateloaded Nanoparticles: Analysis of Drug Content and Study of the Matrix Structure

Chitosan nanoparticles as a new delivery system for the chemotherapy agent tegafur

BACKGROUND

Despite the very efficient antitumor activity of conventional chemotherapy, generally high doses of anticancer molecules must be administered to obtain the required therapeutic action, simultaneously leading to severe side effects. This is frequently a consequence of the development of multidrug resistance by cancer cells and of the poor pharmacokinetic profile of these agents.

OBJECTIVE

In Order to improve the antitumor effect of tegafur and overcome their important drawbacks, we have investigated its incorporation into a drug nanoplatform based on the biodegradable polymer chitosan.

MATERIALS AND METHODS

Two tegafur loading methods were studied: (i) absorption into the polymeric network (entrapment procedure); and (ii) surface deposition (adsorption procedure) in already formed chitosan nanoparticles.

RESULTS

Tegafur entrapment into the polymeric matrix has yielded higher drug loading values and a slower drug release profile, compared to single surface adsorption. The main factores determining the drug loading to chitosan were identified.

DISCUSSION AND CONCLUSION

Such polymeric colloid present very interesting properties for efficient tegafur delivery to cancer.

Study of carbonyl iron/poly(butylcyanoacrylate) (core/shell) particles as anticancer drug delivery systems Loading and release properties

The aim of this study is to develop a detailed investigation of the capabilities of carbonyl iron/poly(butylcyanoacrylate) (core/shell) particles for the loading and release of 5-Fluorouracil and Ftorafur. The anionic polymerization procedure, used to obtain poly(alkylcyanoacrylate) nanoparticles for drug delivery, was followed in the synthesis of the composite particles, except that the polymerization medium was a carbonyl iron suspension. The influence of the two mechanisms of drug incorporation (entrapment in the polymeric network and surface adsorption) on the drug loading and release profiles were investigated by means of spectrophotometric and electrophoretic measurements. The optimum loading conditions were ascertained and used to perform drug release evaluations. Among the factors affecting drug loading, both pH and drug concentration were found to be the main determining ones. For both drugs, the release profile was found to be biphasic, since the drug adsorbed on the surface was released rather rapidly (close to 100% in 1h), whereas the drug incorporated in the polymer matrix required between 10 and 20h to be fully released. The kinetics of the drug release from the core/shell particles was mainly controlled by the pH of the release medium, the type of drug incorporation, and the amount of drug loaded.

Ftorafur loading and controlled release from poly(ethyl-2-cyanoacrylate) and poly(butylcyanoacrylate) nanospheres

In the present work, a method is described to prepare polymeric colloidal nanospheres, consisting of poly(ethyl-2-cyanoacrylate) (PE-2-CA) or poly(butylcyanoacrylate) (PBCA), loaded with the anticancer drug ftorafur. The method is based on the anionic polymerization procedure, often used in the synthesis of poly(alkylcyanoacrylate) nanospheres for drug delivery. A detailed investigation of the capabilities of both polymeric nanoparticles to load this drug is shown. The effect of synthesis residuals and degradation products on the absorbance of supernatants was considered in the loading and release measurement methodologies, because of their potential perturbing influence on the determination of ftorafur concentration in solution. We found the existence of two mechanisms of drug incorporation: absorption or entrapment in the polymeric network, and surface adsorption, detectable by means of zeta potential and spectrophotometric measurements. Among the factors affecting the drug incorporation to the polymer network, the type of polymer, the pH and the drug concentration are the main determining ones. Moreover, the acidity of the medium needs to be controlled in order to avoid the formation of macroaggregates of solids. The optimum loading conditions were used to perform ftorafur release evaluations from polymeric particles, and the influence of the mechanism of drug incorporation, the amount of drug loaded, and the type of polymer on the drug release were studied.

Colloidal stability of magnetite/poly(lactic acid) core/shell nanoparticles

In this work, we describe an experimental investigation on the colloidal stability of suspensions of three kinds of particles, including magnetite, poly(lactic acid) (PLA), and composite core/shell colloids formed by a magnetite core surrounded by a PLA shell. The experiments were performed with dilute suspensions, so that recording the optical absorbance with time gives a suitable indication of the aggregation and sedimentation of the suspensions. The method allowed us to distinguish very accurately between the different surface and magnetic forces responsible for the structures acquired by particle aggregates. Thus, the pure PLA suspensions are very sensitive to ionic strength and almost unaffected by pH changes. On the contrary, the stability of magnetite systems is mainly controlled by pH. The effect of vertical magnetic fields on the stability of magnetite and magnetite/PLA suspensions is also investigated. The PLA shell reduces the magnetic responsiveness of magnetite, but it is demonstrated that the mixed particles can also form structures induced by the field, despite their lower magnetization, and they can be considered in magnetically targeted biomedical applications.

Synthesis and Characterization of Spherical Magnetite/Biodegradable Polymer Composite Particles

A method for preparing colloidal particles formed by a magnetite nucleus and a biodegradable poly(DL-lactide) polymer coating is first described. The method is based on the so-called double-emulsion technique, employed to obtain polymeric spheres loaded with therapeutic drugs, to be used as drug delivery vectors. The aim of this work was to obtain, in a reproducible and rather simple way, colloidal particles that were both magnetic field responsive, and useful as drug delivery systems. In order to investigate to what extent is this target achieved, we compare the structure, chemical composition, and surface properties of the composite particles with those of the nucleus and the coating material. Although the surface properties of the magnetite core are not completely masked, this preliminary study shows that the synthetic new material displays a behavior intermediate between that of magnetite and poly(DL-lactide) spheres. Thus, electrophoresis measurements as a function of pH shows that the isoelectric point (pH(iep)=5.2) of core/shell colloids is in between those of magnetite (pH(iep)=7) and polymer (pH(iep)<2). A similar conclusion is reached when a surface thermodynamic study is performed on the three types of particles: the electron-donor component of the surface free energy of the solids is the quantity that appears to be most sensitive to the surface composition. The fact that poly(DL-lactide) is close to being a nonpolar material gives rise to a measurable decrease in the electron-donor component of the surface free energy, although the effect of coating is also observable in the electron-acceptor and the apolar van der Waals component. Copyright 2001 Academic Press.

Flurbiprofen-loaded nanospheres: analysis of the matrix structure by thermal methods

We report the preparation and evaluation of flurbiprofen loaded-poly-epsilon-caprolactone nanospheres obtained by solvent displacement method. Characterization by thermal methods, infrared spectroscopy and X-ray diffraction analysis can reveal the dispersion state of the drug inside the nanospheres. Such information predicts the stability of the particles and the drug release behaviour. The study has indicated the presence of a molecular dispersed system. In addition, construction of a phase diagram has allowed us to determine the drug/polymer ratios at which flurbiprofen has the highest entrapment efficiency.