Doxorubicin-loaded nanospheres bypass tumor cell multidrug resistance.

We have demonstrated that in vitro resistance of tumor cells to doxorubicin (Dox) can be fully circumvented by using doxorubicin-loaded nanospheres (Dox-NS), consisting of biodegradable polyisohexylcyanoacrylate polymers of 300 nm diameter and containing 2.83 mg of Dox per 31.5 mg of polymer. Five different multidrug-resistant cell lines, characterized by mdr1 amplification, were used in this study: Dox-R-MCF7, a human breast adenocarcinoma; SKVBL1, a human ovarian adenocarcinoma; K562-R, a human erythroleukemia; and two murine lines: P388-Adr-R, a monocytic leukemia of DBA2 mouse, and LR73MDR, a Chinese hamster ovarian cell line. These lines were 38.7, 210, 232, 143 and 20 times more resistant than their corresponding sensitive counterparts, respectively. Using Dox-NS, we obtained complete reversion of drug resistance in vitro, i.e. cell growth inhibition comparable with that obtained with sensitive cells exposed to free Dox. In vivo, we significantly prolonged the survival of DBA2 mice which had previously received P388-Adr-R cells by i.p. injections of Dox-NS, while free Dox injection was ineffective toward this rapidly growing tumor. (Prolongation of survival time: 115% vs 167% after Dox vs Dox-NS treatment, respectively.) Using the MCF7 cell line and its resistant variant, we studied the intracellular concentration and the cytoplasmic and nuclear distribution of Dox by laser microspectrofluorometry (LMSF). In sensitive cells, we observed a similar accumulation and distribution of Dox whatever the form of Dox delivery, i.e. whether free or carried by nanospheres. Analysis by LMSF showed that 99% of intranuclear Dox was bound to DNA after treatment with both forms of Dox. Of Dox, 81 and 83% were found in the intranuclear compartment of sensitive cells incubated with free Dox and Dox-NS, respectively. Resistant cells incubated with Dox-NS accumulated the same amount of Dox as sensitive cells incubated with free Dox or with Dox-NS. Dox, when loaded in nanospheres, bypasses the efflux mechanism responsible for multidrug resistance. LMSF analysis showed that Dox, transported and released by nanospheres, interacts with DNA identically in sensitive and resistant cells.

Isobutyl cyanoacrylate nanoparticles as a solid phase for an efficient immunoradiometric assay.

The interaction of monoclonal antibodies and seric proteins with cyanoacrylic nanoparticles was investigated. A high binding capacity, rapid kinetics of adsorption as well as a good stability of the linkage were found. Furthermore, the immunoreactivity was conserved after coating antibody to nanoparticles. A new competitive immunoradiometric assay was also proposed for determination of alpha-fetoprotein amounts as low as 0.1 ng per assay.

Physicochemical and morphological characterization of polyisobutyl cyanoacrylate nanocapsules.

Two different polymerization mechanisms of alkyl cyanoacrylates were compared with regard to their morphological and physico-chemical characteristics. Cyanoacrylates were polymerized by simple emulsification into an aqueous medium or by interfacial polymerization in an o/w type emulsion. Suspensions of particles obtained by these two mechanisms show dramatic differences when studied for their turbidity, refractive index, and stability following centrifugation. These observations are consistent with the fact that nanoparticles obtained by emulsion polymerization are known to be formed by a full polymer core, while nanocapsules obtained by interfacial polymerization were thought to consist of an internal oil droplet surrounded by a polymeric wall. This theory was further confirmed by an electron microscopic examination of the internal structures of the two types of polymeric aggregates.

Ampicillin-loaded liposomes and nanoparticles: comparison of drug loading, drug release and in vitro antimicrobial activity.

In this paper, we report the physico-chemical properties of negatively charged liposomes and of polyisohexylcyanoacrylate nanoparticles loaded with ampicillin. Although the carriers were of the same size (200 nm), drug-loading capacity was 20 times higher for nanoparticles than for liposomes. After freeze-drying or storage at +4 degrees C, no drug escaped from polymeric nanoparticles. On the other hand, in the same conditions, ampicillin leaked rapidly from liposomes. Drug release in foetal calf serum was gradual (of zero order) with nanoparticles, whereas it was rapid with liposomes. Finally, the antimicrobial activity of ampicillin-entrapped liposomes or nanoparticles was studied in vitro.

Effectiveness of nanoparticle-bound ampicillin in the treatment of Listeria monocytogenes infection in athymic nude mice.

The effectiveness of nanoparticle-bound ampicillin was tested in the treatment of experimental Listeria monocytogenes infection in congenitally athymic nude mice. Nanoparticles of polyisohexylcyanoacrylate (PIHCA) 187 +/- 13 nm in diameter were bound to ampicillin at an ampicillin/PIHCA ratio of 0.2:1. The proportion of ampicillin bound was 90% +/- 3%. After adsorption onto nanoparticles, the therapeutic activity of ampicillin increased dramatically over that in the free state. Thus, 2.4 mg of nanoparticle-bound ampicillin (three doses of 0.8 mg each) had a greater therapeutic effect than 48 mg of free ampicillin (three doses of 16 mg each). These results might provide an incentive for further development of intracellular targeting of antibiotics on biodegradable polymeric carriers.