Research Article
Synthesis of nanodiamond–daunorubicin conjugates to overcome multidrug chemoresistance in leukemia

https://doi.org/10.1016/j.nano.2013.07.014Get rights and content

Abstract

Nanodiamonds (NDs) are promising candidates in nanomedicine, demonstrating significant potential as gene/drug delivery platforms for cancer therapy. We have synthesized ND vectors capable of chemotherapeutic loading and delivery with applications towards chemoresistant leukemia. The loading of Daunorubicin (DNR) onto NDs was optimized by adjusting reaction parameters such as acidity and concentration. The resulting conjugate, a novel therapeutic payload for NDs, was characterized extensively for size, surface charge, and loading efficiency. A K562 human myelogenous leukemia cell line, with multidrug resistance conferred by incremental DNR exposure, was used to demonstrate the efficacy enhancement resulting from ND-based delivery. While resistant K562 cells were able to overcome treatment from DNR alone, as compared with non-resistant K562 cells, NDs were able to improve DNR delivery into resistant K562 cells. By overcoming efflux mechanisms present in this resistant leukemia line, ND-enabled therapeutics have demonstrated the potential to improve cancer treatment efficacy, especially towards resistant strains.

From the Clinical Editor

The authors of this study demonstrate superior treatment properties of resistant leukemia cell lines by utilizing nanodiamond vectors loaded with daunorubicin, paving the way to clinical studies in the hopefully not too distant future.

Graphical Abstract

An artistic rendering of ND-R conjugates approaching a cancer cell. ND particles (green) consist of green spheres representing carbon atoms, while DNR molecules, consisting of teal (carbon), blue (nitrogen), gray (hydrogen), red (oxygen) spheres, are attached to the surface of the ND. When resistance develops in cancer, drug efflux can become a serious issue by removing intracellular therapeutics, as shown by blue arrow depicting the efflux of DNR by efflux pumps (yellow). However, ND-enabled delivery has demonstrated the potential to overcome drug efflux and improve treatment outcome, as shown by the ND-mediated DNR entering the nucleus of the cancer cell.

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Section snippets

ND-R loading and optimization

To form ND-R conjugates, DNR was reversibly loaded onto ND platforms. ND and DNR were mixed at various ratios (w/w), followed by adjusting pH to basic conditions to promote binding. After incubation (5 min, 25 °C), the solution was centrifuged (15 min, 2500 rpm, ~ 1450 g) to pellet bound ND-R. Unbound DNR remained in the supernatant and was subsequently removed. This supernatant was used to quantify unbound DNR to calculate the amount of DNR bound. The pelleted ND-R was resuspended in water using

Results

The ND platform was engineered to form a delivery system capable of combating resistant leukemia by shuttling DNR. Requisite of effective delivery vehicles, NDs have demonstrated outstanding biocompatibility.33, 34, 35 Figure 1, B shows the biocompatibility of varying ND concentrations exposed to K562 cells. Remarkably, cells exhibited > 90% viability after exposure to 0.0005-0.5 mg/ml NDs, compared with < 5% viability for positive control (SDS 1%). ND platforms also possess robust binding

Discussion

Cancer therapies can fail due to increases in activity of cellular efflux mechanisms. Higher levels of chemotherapeutic efflux lead to reductions in intracellular drug concentration and subsequent progression of drug insensitivity.9 The three most prominent MDR transporters typically attributed to chemotherapeutic efflux, are ABCB1 (MDR1, P-glycoprotein), ABCC2 (MRP1), and ABCG2 (BCRP, MXR). Overexpression of these transporters has also been correlated with more aggressive phenotypes of cancer

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      Citation Excerpt :

      Cell line studies on a K562 human myelogenous leukemia cell line with multidrug resistance and augmented daunorubicin exposure was carried out for efficacy enhancement demonstration. NDs enhanced the daunorubicin delivery to resistant cells [71]. NDs are used as a drug carrier mainly in any of the forms viz. NDs assemble on a chemical substrate to form a thin film, having interactions with a drug in two dimensions (forming spontaneous clusters also named as NDs hydrogel with low free energy in an aqueous solution), having interactions with a drug in three dimensions [16].

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    D.H. is a co-author of a patent application associated with nanodiamond drug delivery.

    No conflict of interest was reported by the other authors of this paper.

    D.H. gratefully acknowledges support from the National Science Foundation CAREER Award (CMMI-0846323), Center for Scalable and Integrated NanoManufacturing (DMI-0327077), CMMI-0856492, DMR-1105060, V Foundation for Cancer Research Scholars Award, Wallace H. Coulter Foundation Translational Research Award, Society for Laboratory Automation and Screening (SLAS) Endowed Fellowship, Beckman Coulter, National Cancer Institute grant U54CA151880 (The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute or the National Institutes of Health), and European Commission funding program FP7-KBBE-2009-3. E.K.C. gratefully acknowledges support from the Cancer Science Institute of Singapore (RCE CSI Main Grant) and Ministry of Education Academic Research Fund-Tier 1 grant R-184-000-227-112. H.B.M. gratefully acknowledges support from the Northwestern University Mechanical Engineering Department for the Walter P. Murphy fellowship, terminal year Cabell fellowship, and Predictive Science and Engineering Design (PSED) fellowship. This research used resources of the QUEST cluster at Northwestern University and the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357.

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