Three-dimensional printed isoniazid liposome photothermal composite scaffolds and their performance evaluation

Abstract

BACKGROUND: Drug-loaded bone scaffolds for tuberculosis treatment suffer from problems such as drug burst release in the early stages of treatment and insufficient drug release in the later stages, which leads to low drug concentration at the lesion, therefore, it is imperative to build a drug controlled-release system on the tissue-engineered bone scaffolds. OBJECTIVE: To prepare photothermal composite scaffolds with different isoniazid liposome doping ratios and characterize their mechanical and biological properties. METHODS: Isoniazid liposomes were prepared using the thin-film hydration method. The microstructure, encapsulation efficiency, drug loading capacity, particle size, and Zeta potential of liposomes were characterized. 15 mg of isoniazid was selected as the total drug amount for a single drug-loaded scaffold. Isoniazid drug powder, isoniazid liposome powder at 2%, 5%, and 8% of the total drug amount, respectively, were mixed uniformly with the scaffold base material (hydroxyapatite and β-tricalcium phosphate in a mass ratio of 6:4) and 3% of the photothermal agent polypyrrole nanoparticles (by mass fraction of the scaffold base material) to prepare extrusion printing powders. 13% polyvinyl alcohol gel was added at a mass ratio of 1:1 to the extrusion printing powder, and pure isoniazid scaffolds and three types of isoniazid liposome photothermal scaffolds were fabricated by extrusion-based 3D printing. The microstructure, porosity, mechanical properties, and drug release performance of the photothermal scaffolds were characterized. Mouse embryonic osteoblast MC3T3 cells were cultured with the extracts of the four scaffolds, and the cytotoxicity of the scaffolds was evaluated by MTT assay. RESULTS AND CONCLUSION: (1) Transmission electron microscopy showed that isoniazid liposomes were spherical vesicles with regular shape; the encapsulation efficiency was (28.67±0.62)%, drug loading was (3.54±0.19)%, average particle size was (363.63±10.42) nm, and average Zeta potential was (-4.68±0.72) mV. (2) Scanning electron microscopy showed that compared with pure isoniazid scaffolds, isoniazid liposome photothermal scaffolds had more internal pores; with the increase of isoniazid liposome content, the porosity of photothermal scaffolds increased, while the compressive strength and elastic modulus decreased, but still met the minimum compressive strength required for animal in vivo tissue implantation experiments. The incorporation of isoniazid liposomes effectively solved the drug burst release in the early stage, and the cumulative release rate in the early stage was inversely proportional to the doping amount of isoniazid liposomes. After irradiation with 808 nm near-infrared laser, the cumulative release rate of isoniazid liposome photothermal scaffolds increased compared with that without near-infrared laser irradiation, and with the increase of isoniazid liposome doping amount, the photothermal controlled-release performance in the later stage became more significant. MTT assay showed that the relative proliferation rates of MC3T3 cells cultured with the extracts of the four scaffolds for 24, 72, and 120 h were all greater than 70%, indicating no obvious cytotoxicity. The results indicate that isoniazid liposome photothermal scaffolds have good mechanical properties, drug controlled-release performance, and cytocompatibility.

1. Introduction

Bone tuberculosis is a common clinical disease caused by Mycobacterium tuberculosis, accounting for about 10% of extrapulmonary tuberculosis cases, and is a secondary infectious lesion [1-3]. Currently, the main clinical treatment for bone tuberculosis is surgical debridement followed by oral or injection of anti-tuberculosis drugs such as isoniazid, rifampicin, and streptomycin [4-5]. However, this treatment has two major drawbacks: on one hand, it is difficult to ensure effective bactericidal concentration at the lesion site through drug transport via body fluids, and the relatively closed environment and slow metabolism at the lesion site lead to long-term low drug concentration, which easily induces drug resistance in Mycobacterium tuberculosis [6]; on the other hand, long-term and large-dose systemic drug administration can cause toxic side effects on other organs, leading to related complications. Therefore, developing a treatment method that is long-term effective and allows controlled anti-tuberculosis drug concentration in the body has become the key to the treatment of bone tuberculosis.

In recent years, bone tissue engineering scaffolds prepared by 3D bioprinting technology have provided an effective method for the treatment of bone tuberculosis [7-8]. The scaffold provides mechanical support at the bone defect site, replacing autologous bone, and carries corresponding anti-tuberculosis drugs for local sustained release, matching the drug release with the bone defect repair cycle, maintaining effective bactericidal concentration at the lesion while avoiding toxic side effects of anti-tuberculosis drugs on the liver and kidneys [9]. Therefore, combining anti-tuberculosis drugs with scaffold materials through 3D printing to control drug release behavior at the lesion site [10] has become a hot research direction in the treatment of bone tuberculosis [11]. SHAO et al. [12] blended lidocaine, silver phosphate, and polycaprolactone to prepare printing paste, and fabricated composite drug-loaded scaffolds for antibacterial and analgesic purposes via extrusion-based 3D printing. LIN Zhidong [13] immersed pre-printed polyvinyl alcohol/β-tricalcium phosphate scaffolds in icariin solution with stirring to load drugs by impregnation; the drug release from the scaffold showed a linear trend and improved the bioactivity of the scaffold to some extent. LI Xingyu et al. [14] prepared vancomycin hydrochloride microspheres by emulsion solvent evaporation method, and combined the microspheres with scaffold materials to prepare composite drug-loaded scaffolds; in vitro release experiments showed that the drug release rate within one week was relatively high.