Paclitaxel and quercetin nanoparticles co-loaded in microspheres to prolong retention time for pulmonary drug delivery

Abstract

High drug resistance, poor water solubility, short half-life, and low local drug concentration are obstacles for successful delivery of chemotherapeutic drugs for lung cancer. A new method involving the use of nanoparticles (NPs) for pulmonary delivery is proposed. However, use of NPs is limited by the particle size range for pulmonary drug delivery considering that NPs cannot be deposited directly into the lungs. NPs polymerized into microspheres (polymeric microspheres, PMs) will result in suitable particle sizes and retain the advantages of nanodrugs after redispersion when applied in pulmonary delivery. We report the development of novel NPs in the form of PMs loaded with paclitaxel (PTX) and quercetin (QUE) double drugs based on the synthesis of oleic acid-conjugated chitosan (OA-CTS) for pulmonary delivery. This approach is aimed toward prolonging PTX retention time in the presence of QUE and bypassing P-glycoprotein drug efflux pumps. NPs loaded with PTX or QUE were prepared with 11% substitution degree using OA-CTS as the carrier by ionic cross-linking method, which NPs loaded with PTX or QUE were used in the preparation of PMs by spray-drying. The diameters of the PMs ranged from 1 to 5 μm which had uniform size range. Scanning electron microscopy showed that PMs were polymers formed by a large number of NPs and readily redispersed (after redispersion, size of NPs ranged between 250 and 350 nm) in water within 1 h. PMs displayed slow-release characteristics at pH 4.5 and 7.4. The in vivo pharmacokinetic and biodistribution studies suggested that PMs exhibit prolonged circulation time and a markedly high accumulation in the lung. The obtained results indicate that PMs can serve as a promising pulmonary delivery system for combined pharmacotherapy using hydrophobic anticancer drugs.

Keywords: nanoparticles; oleic acid-conjugated chitosan; paclitaxel; polymeric microspheres; pulmonary delivery; quercetin.

Figure 1

(A) FT-IR spectra of CTS and the mixtures of OA and CTS at weight ratios from 1:5 to 4:5. (B) FT-IR spectra of CTS, OA-CTS, OA-CNPs, PTX, PTX-OA-CNPs, QUE, QUE-OA-CNPs, blank PMs, and PMs. (C) DSC thermograms and (D) XRD patterns of OA-CTS, PTX, PTX-OA-CNPs, QUE, QUE-OA-CNPs, physical mixture of all solid objects, and PMs. Abbreviations: FT-IR, Fourier transform infrared spectroscopy; CTS, chitosan; OA, oleic acid; OA-CTS, OA-conjugated CTS; OA-CNPs, OA-CTS nanoparticles; PTX, paclitaxel; PTX-OA-CNPs, nanoparticles loaded with PTX; QUE, quercetin; QUE-OA-CNPs, nanoparticles loaded with QUE; PMs, polymeric microspheres; DSC, differential scanning calorimetry; XRD, X-ray diffraction.

Figure 2

TEM image of (A) OA-CNPs, (B) PTX-OA-CNPs, and (C) QUE-OA-CNPs. (D) Particle size and PDI of NPs after redispersibility of PMs at 37°C as a function of time. Abbreviations: TEM, transmission electron microscopy; OA-CNPs, oleic acid-conjugated chitosan NPs; PTX-OA-CNPs, NPs loaded with paclitaxel; QUE-OA-CNPs, nanoparticles loaded with quercetin; PDI, polydispersity index; NPs, nanoparticles; PMs, polymeric microspheres.

Figure 3

(A) Schematic illustration of PMs and the redispersed PMs. SEM image of PMs with scale bar of (B) 5 μm, (C) 2 μm, and (D) 500 nm. (E) TEM analysis of particle size distribution and zeta potential after redispersibility of PMs. Abbreviations: PMs, polymeric microspheres; PDI, polydispersity index; SEM, scanning electron microscopy; TEM, transmission electron microscopy; PTX-OA-CNPs, nanoparticles loaded with paclitaxel; QUE-OA-CNPs, nanoparticles loaded with quercetin.

Figure 4

In vitro release profiles of QUE, PTX, and PMs obtained using the dialysis method at 37°C in (A) 0.2 M PBS (pH 7.4) and (B) 0.2 M PBS (pH 4.5). Data shown are the mean ± standard deviations (n=3). Abbreviations: QUE, quercetin; PTX, paclitaxel; PMs, polymeric microspheres; PBS, phosphate buffer saline.

Figure 5

(A) Percentage hemolysis versus concentration of PMs. Data shown are the mean ± standard deviations (n=3, **P<0.01). (B) Hemolysis assay of PTX, QUE, and PMs. Abbreviations: PMs, polymeric microspheres; PTX, paclitaxel; QUE, quercetin.

Figure 6

(A) The mean plasma concentration–time profiles of PTX and QUE after single intravenous administration and combined intravenous administration in rat plasma. (B) The mean plasma concentration–time profiles of PTX and QUE after combined intravenous administration and pulmonary administration in rat plasma. Data shown are the mean ± standard deviations (n=6). Abbreviations: PTX, paclitaxel; QUE, quercetin; PMs, polymeric microspheres.

Figure 7

Concentration of PTX and QUE accumulated in different organs measured using HPLC at 0.5, 1, 3, and 6 h after (A and B) single intravenous administration, (C and D) combined intravenous administration, and pulmonary administration (E and F). Abbreviations: PTX, paclitaxel; QUE, quercetin; HPLC, high-performance liquid chromatography.

Scheme 1

Synthesis and preparation scheme of PMs. Abbreviations: PMs, polymeric microspheres; CTS, chitosan; OA, oleic acid; OA-CTS, OA-conjugated CTS; EDC, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; NHS, N-hydroxysuccinimide; PTX, paclitaxel; TPP, sodium tripolyphosphate; QUE, quercetin; PTX-OA-CNPs, nanoparticles loaded with PTX; QUE-OA-CNPs, nanoparticles loaded with QUE.