Chiral mesoporous silica nano-screws as an efficient biomimetic oral drug delivery platform through multiple topological mechanisms

Abstract

In the microscale, bacteria with helical body shapes have been reported to yield advantages in many bio-processes. In the human society, there are also wisdoms in knowing how to recognize and make use of helical shapes with multi-functionality. Herein, we designed atypical chiral mesoporous silica nano-screws (CMSWs) with ideal topological structures (e.g., small section area, relative rough surface, screw-like body with three-dimension chirality) and demonstrated that CMSWs displayed enhanced bio-adhesion, mucus-penetration and cellular uptake (contributed by the macropinocytosis and caveolae-mediated endocytosis pathways) abilities compared to the chiral mesoporous silica nanospheres (CMSSs) and chiral mesoporous silica nanorods (CMSRs), achieving extended retention duration in the gastrointestinal (GI) tract and superior adsorption in the blood circulation (up to 2.61- and 5.65-times in AUC). After doxorubicin (DOX) loading into CMSs, DOX@CMSWs exhibited controlled drug release manners with pH responsiveness in vitro. Orally administered DOX@CMSWs could efficiently overcome the intestinal epithelium barrier (IEB), and resulted in satisfactory oral bioavailability of DOX (up to 348%). CMSWs were also proved to exhibit good biocompatibility and unique biodegradability. These findings displayed superior ability of CMSWs in crossing IEB through multiple topological mechanisms and would provide useful information on the rational design of nano-drug delivery systems.

Keywords: APTES, 3-aminopropyltriethoxysilane; AR, aspect ratio; AUC0‒∞, area under the curve; CMSRs, chiral mesoporous silica nanorods; CMSSs, chiral mesoporous silica nanospheres; CMSWs, chiral mesoporous silica nano-screws; CMSs, chiral mesoporous silicas nanoparticles; Cd, drug loading capacity; Chiral mesoporous silica; Cmax, maximum concentration; DAPI, 4,6-diamidino-2-phenylindole; DCM, dichloromethane; DOX, doxorubicin; EDC·HCl, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; FBS, fetal bovine serum; FITC, Fluorescein isothiocyanate; Frel, relative bioavailability; GI, gastrointestinal; Geometric topological structure; HOBT, 1-hydroxybenzotriazole; IEB, intestinal epithelium barrier; IR, infrared spectroscopy; Intestinal epithelium barrier; MRT0‒∞, mean residence time; MSNs, mesoporous silica nanoparticles; Morphology; Mβ-CD, methyl-β-cyclodextrin; N-PLA, N-palmitoyl-l-alanine; NPs, nanoparticles; Nano-screw; Oral adsorption; PBS, phosphate buffer solution; RBCs, red blood cells; RITC, rhodamine B isothiocyanate; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SBET, Specific surface area; SBF, simulated body fluid; SD, Sprague–Dawley; SGF, simulated gastric fluid; SIF, simulated intestinal fluid; TEOS, ethylsilicate; Tmax, peak time; Vt, pore volume; WBJH, pore diameter; XRD, X-ray diffractometry; nano-DDS, nano-drug delivery systems; t1/2, half-life.

Graphical abstract

Figure 1

The formation mechanism (A), representative TEM images (B and C), representative SEM images of CMSs (D), and hydrodynamic diameters (E, based on the dynamic light scattering tests) of CMSs.

Figure 2

SAXS patterns (A), pore size distributions (B) and N₂ adsorption–desorption isotherms (C) of CMSs. (D) Zeta potential of CMSs. Data are presented as the mean ± SD of the mean (n = 3). (E) Contact angles of CMSs measured at the initial 5 s, the middle 25 s and the last 55 s. (F) The variation tendency of contact angles with time.

Figure 3

In vivo and in vitro bio-retention of CMSs with different morphologies. (A) The conceptual comparison in the sectional area and contact area of sphere, rod-shaped and screw-like structures. (B) Bio-retention images of CMSs on the mucus layer of small intestine (the white circles show the average fluorescence intensity of CMSs, indicating the bio-retention performance of CMSs). (C) Bio-retention profiles of CMSs on the mucus layer of small intestine. (D) Time-dependent plasma concentration of CMSs after oral administration. (E) Images of CMSs remained in the whole GI tract at different intervals after oral administration. (F and G) The average radiance of CMSs in stomach and small intestine at different times, respectively. Data are presented as the mean ± SD of the mean (n = 3). ∗P < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001.

Figure 4

(A) Schematic illustration of CMSs with different topological structures in crossing IEB (mainly including the mucus layer and epithelial cells). (B) Three-dimensional images of mucoadhesion and mucus penetration. Green: mucus stained with RITC. Red: NPs. Scale bar = 50 μm. Depth: 70 μm. (C) The representative trajectories of CMSs in mucus solutions at 2 and 10 s.

Figure 5

(A) CLSM images of Caco-2 cells after incubation with FITC-CMSs for 4 h. Scale bar=50 μm. (B) Cellular uptake amounts of CMSs after incubation with specific inhibitors quantified by Image J software. (C) CLSM images of Caco-2 cells after incubation with FITC-CMSs in the presence of specific inhibitors: cytochalasin D, chlorpromazine and Mβ-CD. Scale bar = 30 μm. Data are presented as the mean ± SD of the mean (n = 3). ∗P < 0.05 and ∗∗P < 0.01.

Figure 6

(A) XRD patterns of CMSs before and after DOX loading, indicating the successful drug loading. (B) In vitro release profiles of DOX and DOX@CMSs in pH 7.4 PBS. (C) In vitro release profiles of DOX@CMSWs in PBS medium with different pH values (pH 7.4, pH 6.5 and pH 5.0). (D) Plasma concentration vs time curves of DOX and DOX@CMSs in SD rats after oral administration. (E) CLSM images of DOX absorption at intestinal tissue acquired at 2 h after oral administration. Blue: nuclei of the intestinal villi stained with DAPI. Red: Dox.

Figure 7

The calculated degradation rate of the CMSs after 48 h (A) and 1 week (B) of biodegradation. (C) TEM images of CMSs in SGF (d1, d4, d7), SIF (d2, d5, d8), and SBF (d3, d6, d9) after biodegradation for 1 week. (D) Hemolysis ratio of RBCs treated with CMSWs at different concentrations ranging from 25 to 800 μg/mL for 4 h. (E) Hemolytic photographs of RBCs incubated with different concentrations of CMSWs for 0.5 h (a1), 2 h (a2), 4 h (a3) and centrifugation after 4 h (a4) with D.I. water (+) and sterile normal saline (−) as positive and negative control, respectively. The presence of red hemoglobin in the supernatant indicates the damaged RBCs. (F) The H&E staining images of major tissues (heart, liver, spleen, lung and kidney) at the end of treatments of CMSWs. Data are represented as mean ± SD of the mean (n = 3). Scale bar = 200 nm.