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We identified that the chemical linkage of the anticancer drug doxorubicin onto squalene, a natural lipid precursor of the cholesterol's biosynthesis, led to the formation of squalenoyl doxorubicin (SQ-Dox) nanoassemblies of 130-nm mean diameter, with an original "loop-train" structure. This unique nanomedicine demonstrates: (i) high drug payload, (ii) decreased toxicity of the coupled anticancer compound, (iii) improved therapeutic response, (iv) use of biocompatible transporter material, and (v) ease of preparation, all criteria that are not combined in the currently available nanodrugs. Cell culture viability tests and apoptosis assays showed that SQ-Dox nanoassemblies displayed comparable antiproliferative and cytotoxic effects than the native doxorubicin because of the high activity of apoptotic mediators, such as caspase-3 and poly(ADP-ribose) polymerase. In vivo experiments have shown that the SQ-Dox nanomedicine dramatically improved the anticancer efficacy, compared with free doxorubicin. Particularly, the M109 lung tumors that did not respond to doxorubicin treatment were found inhibited by 90% when treated with SQ-Dox nanoassemblies. SQ-Dox nanoassembly-treated MiaPaCa-2 pancreatic tumor xenografts in mice decreased by 95% compared with the tumors in the saline-treated mice, which was significantly higher than the 29% reduction achieved by native doxorubicin. Concerning toxicity, SQ-Dox nanoassemblies showed a fivefold higher maximum-tolerated dose than the free drug, and moreover, the cardiotoxicity study has evidenced that SQ-Dox nanoassemblies did not cause any myocardial lesions, such as those induced by the free doxorubicin treatment. Taken together, these findings demonstrate that SQ-Dox nanoassemblies make tumor cells more sensitive to doxorubicin and reduce the cardiac toxicity, thus providing a remarkable improvement in the drug's therapeutic index.

A rapid and sensitive high performance liquid chromatographic (HPLC) assay utilizing fluorimetric detection (excitation at 480 nm, emission at 560 nm) for the determination of doxorubicin in dog blood was developed and validated. Treatment of blood samples containing doxorubicin with AgNO3 (as protein precipitant) resulted in appearance of an additional peak in the chromatogram of doxorubicin at 11.5 min along with the parent peak (tR = 5.5 min). The latter peak was not found when treated with other protein precipitants such as trichloroacetic acid and methanol. Construction of a calibration curve based on the area of the first peak alone did not result in linearity of the curve. However, summation of areas of both peaks resulted in a curve with good linearity and coefficient of determination (R2 = 0.9985). Appearance of the second peak may be due to the interaction of doxorubicin with cellular components of blood in the presence of AgNO3 leading to the formation of a complex with reduced polarity. Analysis of the quality control samples showed good accuracy (96.7-100.42) and precision (RSD = 2.6-5.7%). The proposed method could be advantageous in estimation of doxorubicin incorporated into targeted delivery systems that concentrate in blood cells and quantify the absolute blood concentration of doxorubicin.

The aim of the study is to determine and compare the pharmacokinetics and tissue distribution of Doxorubicin (Dox) delivered as solution or through nanoparticles after intravenous (i.v.) and intraperitoneal (i.p.) injection. Doxorubicin loaded poly(butyl cyanoacrylate) nanoparticles were synthesized by dispersion polymerization (DP) and emulsion polymerization (EP) techniques. The drug loaded DP and EP nanoparticles were administered by i.v. or i.p. routes and the respective pharmacokinetics and tissue distribution were determined. Both types of nanoparticles significantly enhanced the elimination half-life (T(1/2)), mean residence time (MRT) AUC(0-8), AUC(0-infinity) and AUMC(0-8) of Dox in blood after i.v. injection. Dox delivered through DP nanoparticles rapidly disappeared from blood and distributed to the organs of reticuloendothelial system (RES). But, the clearance of Dox delivered through EP nanoparticles from blood was slower than this of the DP nanoparticles and Dox solution. After i.p. injection, the Dox loaded into DP nanoparticles quickly appeared in blood and undergone rapid distribution to the organs of RES, while the Dox loaded into EP nanoparticles absorbed slowly into blood and remained in the circulation for longer time. The absorption into blood of Dox delivered through DP and EP nanoparticles after i.p. injection was relatively rapid and higher than Dox solution. The T(1/2), MRT, AUC(0-8), AUC(0-infinity) and AUMC(0-8) of Dox in blood were significantly higher and the clearance (Cl) was lower than for the Dox solution after i.p. injection. The tissue concentrations of Dox delivered through nanoparticles after i.p. injection were significantly lower than after i.v. injection. The bioavailability (F) of Dox was greatly enhanced by DP (approximately 1.9 fold) and EP nanoparticles (approximately 2.12 fold) compared to Dox solution after i.p. injection. EP nanoparticles significantly enhanced the bioavailability, MRT, T(1/2), AUC(0-8), AUC(0-infinity) and AUMC(0-8) of Dox than DP nanoparticles. This signifies the advantage of EP nanoparticles in increasing the elimination half-life of Dox both after i.v. and i.p. injection and enhanced bioavailability after i.p. injection, which is expected to improve the therapeutic efficacy of Dox and reduce the Dox-associated systemic toxicity. Importantly, both DP and EP nanoparticles greatly reduced the distribution of Dox to heart both after i.v. and i.p. injection, suggesting their potential in reducing Dox-associated cardiotoxicity.

The objective of this study is to enhance the delivery of Doxorubicin hydrochloride to Dalton's lymphoma solid tumour through poly(butyl cyanoacrylate) (PBC) nanoparticles. Doxorubicin loaded PBC (DPBC) nanoparticles were prepared by emulsion polymerization and characterized by particle size analysis, zeta potential and scanning electron microscopy. Doxorubicin HCl (Dox) and DPBC nanoparticles were radiolabeled with 99mTc by reduction method using stannous chloride and optimized the labeling parameters to obtain high labeling efficiency. The in vitro stability of 99mTc-labeled complexes was determined by DTPA and cysteine challenge test. The labeled complexes showed very low transchelation and high in vitro and serum stability. 99mTc labeled complexes of Dox and DPBC nanoparticles were administered subcutaneously below the Dalton's lymphoma tumour and biodistribution was studied. The distribution of DPBC nanoparticles to the blood, heart and organs of RES such as liver, lung and spleen was biphasic with a rapid initial distribution, followed by a significant decrease later at 6 h post-injection. The distribution of Dox to tissues was very low initially and increased significantly at 6 h post-injection indicating its accumulation at the injection site for a longer time. The concentration of DPBC nanoparticles was also found high in tissues at 6 h post-injection indicating their accumulation at the subcutaneous site and consequent disposition to tissues with time. A significantly high tumour uptake of DPBC nanoparticles (approximately 13 fold higher at 48 h post-injection) (P <0.001) was found compared to free Dox. The tumour concentrations of both Dox and DPBC nanoparticles increased with time indicating their slow penetration from the injection site into tumour. The concentration of DPBC nanoparticles in the femur bone in the tumour region was also significantly higher (P <0.001) than free Dox and increased with time. The study signifies the advantage of delivering Dox to Dalton's lymphoma through PBC nanoparticles by facilitating enhanced tumour uptake and prolonged tumour retention, which are expected to lead to greater therapeutic effect in the form of tumour regression.