Strategy for chemotherapeutic delivery using a nanosized porous metal-organic framework with a central composite design

Abstract

Background: Enhancing drug delivery is an ongoing endeavor in pharmaceutics, especially when the efficacy of chemotherapy for cancer is concerned. In this study, we prepared and evaluated nanosized HKUST-1 (nanoHKUST-1), nanosized metal-organic drug delivery framework, loaded with 5-fluorouracil (5-FU) for potential use in cancer treatment.

Materials and methods: NanoHKUST-1 was prepared by reacting copper (II) acetate [Cu(OAc)₂] and benzene-1,3,5-tricarboxylic acid (H₃BTC) with benzoic acid (C₆H₅COOH) at room temperature (23.7°C±2.4°C). A central composite design was used to optimize 5-FU-loaded nanoHKUST-1. Contact time, ethanol concentration, and 5-FU:material ratios were the independent variables, and the entrapment efficiency of 5-FU was the response parameter measured. Powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption were used to determine the morphology of nanoHKUST-1. In addition, 5-FU release studies were conducted, and the in vitro cytotoxicity was evaluated.

Results: Entrapment efficiency and drug loading were 9.96% and 40.22%, respectively, while the small-angle X-ray diffraction patterns confirmed a regular porous structure. The SEM and TEM images of the nanoHKUST-1 confirmed the presence of round particles (diameter: approximately 100 nm) and regular polygon arrays of mesoporous channels of approximately 2-5 nm. The half-maximal lethal concentration (LC₅₀) of the 5-FU-loaded nanoHKUST-1 was approximately 10 µg/mL.

Conclusion: The results indicated that nanoHKUST-1 is a potential vector worth developing as a cancer chemotherapeutic drug delivery system.

Keywords: 5-fluorouracil; drug delivery; nano-MOFs; nanoparticles.

Figure 1

Low-angle and wide-angle XRD spectra of nanoHKUST-1. Notes: (A) Low-angle XRD spectra of nanoHKUST-1. Small peak at 2–3 indicates internal regular porous structure, which confirms sample was a porous material. (B) Wide-angle XRD spectra of nanoHKUST-1. XRD patterns of synthetic nanoHKUST-1 (black) and standard HKUST-1 (red). XRD patterns of sample show same peaks as those of standard, which confirms the high purity of nanoHKUST-1. Peaks patterns of sample account for rough appearance of nanosized particles. Abbreviations: XRD, X-ray diffraction; nanoHKUST-1, nanosized HKUST-1.

Figure 2

SEM and TEM images of morphology of nanoHKUST-1. Notes: (A) SEM images of morphology of nanoHKUST-1. Particles show regular round, uniform distribution, with no adhesion and a size of 50–100 nm. Single-particle surface is rough, indicating existence of pores. (B) TEM images of morphology of nanoHKUST-1 showing a pore diameter of 2–5 nm. The white part of the inset in B is pore canal, and the black part is pore wall. Abbreviations: SEM, scanning electron microscopy; TEM, transmission electron microscopy; nanoHKUST-1, nanosized HKUST-1.

Figure 3

Nitrogen adsorption–desorption isotherms and pore size distribution of HKUST-1. Notes: (A) Nitrogen adsorption–desorption isotherms. Hysteresis loop phenomenon appears in the range of relative high pressure, indicating the existence of channels in sample. (B) BJH pore size distributions. First peak shows average pore size was approximately 2–5 nm. Peak approximately 10 nm wide was caused by interstitial pore generated by accumulation of particles. P refers to liquid nitrogen saturation vapour pressure; P₀ refers to equilibrium vapour pressure; v refers to pore volume; r refers to pore radius. Abbreviation: BJH, of Barrett-Joyner-Halenda.

Figure 4

SEM images of morphology of 5-FU-loaded nanoHKUST-1. Morphological structure of carriers was not obviously changed compared with that of drug-loaded carriers. Abbreviations: SEM, scanning electron microscopy; 5-FU, 5-fluorouracil.

Figure 5

DSC patterns. Notes: Patterns of (A) 5-FU, (B) nanoHKUST-1, and (C) 5-FU-loaded nanoHKUST-1. Result shows curves before and after drug loading were similar and began to decompose at 337.5°C, while 5-FU decomposed at 272°C. Drug-loading process proved to have no effect on thermal stability of nanoHKUST-1. Abbreviations: DSC, differential scanning calorimetry; 5-FU, 5-fluorouracil; nanoHKUST-1, nanosized HKUST-1; DTA, differential thermal analysis.

Figure 6

Three-dimensional map of X₁ (contact time), X₂ (ethanol concentration), and X₃ (5-FU:nanoHKUST-1 ratios) after interaction of independent variables. Optimized ethanol concentration was 70%, drug-loading ratio was 7:1, and delivery time was 96 h. Abbreviations: 5-FU, 5-fluorouracil; nanoHKUST-1, nanosized HKUST-1.

Figure 7

In vitro release curves for 5-FU (blue line) and 5-FU-loaded nanoHKUST-1 (red line). After approximately 10 h, 90% of 5-FU was found in release medium, while only 60% of drug was released from NPs. Every trial was repeated three times. All values are shown as mean ± SD. Abbreviations: 5-FU, 5-fluorouracil; NPs, nanoparticles; SD, standard deviation; nanoHKUST-1, nanosized HKUST-1.

Figure 8

Comparison of cytotoxicities of 5-FU, empty nanoHKUST-1, and 5-FU-loaded nanoHKUST-1 using MTT assay. Toxicity of nanoHKUST-1 was lowest, while that of 5-FU-loaded nanoHKUST-1 was highest. Each concentration was repeated in six wells. All values are shown as mean ± SD. Abbreviations: 5-FU, 5-fluorouracil; SD, standard deviation; nanoHKUST-1, nanosized HKUST-1.