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The effect of ligand lipophilicity on the nanoparticle encapsulation of Pt(IV) prodrugs.

ABSTRACT: In an effort to expand the therapeutic range of platinum anticancer agents, several new approaches to platinum-based therapy, including nanodelivery, are under active investigation. To better understand the effect of ligand lipophilicity on the encapsulation of Pt(IV) prodrugs within polymer nanoparticles, the series of compounds cis,cis,trans-[Pt(NH3)2Cl2L2] was prepared, where L = acetate, propanoate, butanoate, pentanoate, hexanoate, heptanoate, octanoate, nonanoate, and decanoate. The lipophilicities of these compounds, assessed by reversed-phase HPLC, correlate with the octanol/water partition coefficients of their respective free carboxylic acid ligands, which in turn affect the degree of encapsulation of the Pt(IV) complex within the hydrophobic core of poly(lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-PEG-COOH) nanoparticles. The most lipophilic compound investigated, cis,cis,trans-[Pt(NH3)2Cl2(O2C(CH2)8CH3)2], displayed the best encapsulation. This compound was therefore selected to evaluate the effect of increased platinum concentration on encapsulation. As the platinum concentration was increased, there was an initial increase in encapsulation followed by a decrease due to macroscopic precipitation. Maximal loading occurred when the platinum complex was present at a 40% w/w ratio with respect to polymer during the nanoprecipitation step. Particles formed under these optimal conditions had diameters of approximately 50 nm, as determined by transmission electron microscopy.

SUBMITTER: Johnstone TC

PROVIDER: S-EPMC3773226 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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The effect of ligand lipophilicity on the nanoparticle encapsulation of Pt(IV) prodrugs.

Johnstone Timothy C TC Lippard Stephen J SJ

Inorganic chemistry 20130716 17

In an effort to expand the therapeutic range of platinum anticancer agents, several new approaches to platinum-based therapy, including nanodelivery, are under active investigation. To better understand the effect of ligand lipophilicity on the encapsulation of Pt(IV) prodrugs within polymer nanoparticles, the series of compounds cis,cis,trans-[Pt(NH3)2Cl2L2] was prepared, where L = acetate, propanoate, butanoate, pentanoate, hexanoate, heptanoate, octanoate, nonanoate, and decanoate. The lipoph ...[more]

PMID: 23859129

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Project description:Over the last decades, gold nanoparticles (AuNPs) have proven to be remarkable tools for drug delivery and theranostic applications in cancer treatment. On the other hand, Pt(IV) prodrugs have been employed as an interesting alternative to the more common Pt(II) complexes, such as cisplatin, for cancer chemotherapy. Searching to design an image-guided nanocarrier to deliver selectively Pt(IV) prodrugs to tumors expressing the gastrin releasing peptide receptor (GRPR), we have synthesized small core AuNPs carrying a thiolated DOTA derivative, a GRPR-targeting bombesin analog (BBN[7-14]) and a Pt(IV) prodrug attached to the AuNPs without (AuNP-BBN-Pt1) or with a PEGylated linker (AuNP-BBN-Pt2 and AuNP-BBN-Pt3). In the GRPR+ prostate cancer PC3 cell line, the cytotoxic activity of the designed AuNP-BBN-Pt nanoparticles is strongly influenced by the presence of the PEGylated linker. Thus, AuNP-BBN-Pt1 displayed the lowest IC50 value (9.3 ± 2.3 µM of Pt), which is comparable to that exhibited by cisplatin in the same cell line. In contrast, AuNP-BBN-Pt1 showed an IC50 value of 97 ± 18 µM of Pt in the non-tumoral RWPE-1 prostate cells with a much higher selective index (SI) towards PC3 cells (SI = 10) when compared with cisplatin (SI = 1.3). The AuNPs were also successfully labeled with 67Ga and the resulting 67Ga-AuNP-BBN-Pt were used to assess their cellular uptake in PC3 cells, with AuNP-BBN-Pt1 also displaying the highest cellular internalization. Finally, intratumoral administration of 67Ga-AuNP-BBN-Pt1 in a PC3 tumor-bearing mice showed a prolonged retention of the nanoparticle compared to that of cisplatin, with optimal in vivo stability and 20% of the injected platinum remaining in the tumor after 72 h post-injection. Furthermore, microSPECT imaging studies confirmed the uptake and considerable retention of the 67Ga-labeled AuNPs in the tumors. Overall, these results show the potential of these targeted AuNPs loaded with Pt(IV) prodrugs for prostate cancer theranostics.

Project description:The possibility of spontaneous self-assembly of dicarboxylato Pt(IV) prodrugs and the consequences on their uptake in cancer cells have been evaluated in different aqueous solutions. Four Pt(IV) complexes, namely, (OC-6-33)-diacetatodiamminedichloridoplatinum(IV), Ace, (OC-6-33)-diamminedibutanoatodichloridoplatinum(IV), But, (OC-6-33)-diamminedichloridodihexanoatoplatinum(IV), Hex, and (OC-6-33)-diamminedichloridodioctanoatoplatinum(IV), Oct, have been dispersed in i) milliQ water, ii) phosphate buffered saline, and iii) complete cell culture media (RPMI 1640 or DMEM) containing fetal bovine serum (FBS). The samples have been analyzed by dynamic light scattering (DLS) to measure the size and distribution of the nanoparticles possibly present. The zeta potential offered an indication of the stability of the resulting aggregates. In the case of the most lipophilic compounds of the series, namely, Oct and to a lesser extent Hex, the formation of nanosized aggregates has been observed, in particular at the highest concentration tested (10 μM). The cell culture media had the effect to disaggregate these nanoparticles, mainly by virtue of their albumin content, able to interact with the organic chains via noncovalent (hydrophobic) interactions. For Oct, at the highest concentration employed for the uptake tests (10 μM), the combination between passive diffusion and endocytosis of the self-assembled nanoparticles makes the cellular uptake higher than in the presence of passive diffusion only. During the study of cellular uptake on A2780 ovarian cancer cells pretreated with cytochalasin D, a statistically significant inhibition of endocytosis was observed for Oct. In these experimental conditions, the relationship between uptake and lipophilicity becomes almost linear instead of exponential. Since Oct anticancer prodrug is active at nanomolar concentrations, where the aggregation in culture media is almost abolished, this phenomenon should not significantly impact its antiproliferative activity.

Dataset Information

The effect of ligand lipophilicity on the nanoparticle encapsulation of Pt(IV) prodrugs.

Publications

The effect of ligand lipophilicity on the nanoparticle encapsulation of Pt(IV) prodrugs.

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