Biomimetic electrospun polyurethane matrix composites with tailor made properties for bone tissue engineering scaffolds

Highlights

• Electrospun polyurethane added with oil and metallic particles were developed.

• The added constituents induced a change in surface properties of polyurethane.

• A change in the surface roughness were indicated for electrospun composites.

• The composites showed improved anticoagulant nature than polyurethane.

• Enhanced properties of the composites may be beneficial for bone tissue growth.

Abstract

Bone tissue scaffolds require appropriate properties conducive for new tissue growth. In this study, we prepared a novel electrospun nanofiber scaffold using polyurethane (PU), rosemary (RM) oil and copper sulphate (CuSO₄) respectively. The properties of the developed membranes were established through scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA), contact angle and mechanical testing. Further, blood compatibility and cytocompatibility assay were carried out to evaluate their biological responses. The developed composites rendered appropriate surface morphology with tailor made wettability and roughness. Composites with engineered physicochemical properties improved the blood and cytocompatible properties which can be potentially exploited for bone tissue engineering applications.

Introduction

Bone fraction as a result of trauma and bone diseases leads to a large bone defect which is quite a common problem and needs treatment to remodel the damaged tissue [1]. The conventional method used to remodel the damaged bone tissue was autogenous and allogenous bone grafting. They are considered as a golden standard for repairing the bone tissue and it was limited in clinical applications owing to some problems like limited donor supply, low level of immunity and infections [2]. The demand for orthopaedics devices was increasing day by day. The current global market value of orthopaedics technologies was reported to be $41.9 billion and it will reach $56.2 billion at the end of the year 2023 with CAGR of 4.7% [3]. With the advent of the technology, tissue engineering holds promising alternate for because it was reported to overcome the limitations of the conventional method. Tissue engineering (TE) comprises of three basic components (scaffolds, cells and scaffold and growth factors) in order to regenerate the new tissue growth. Among three components, scaffold is an important component as a substrate for cell adhesion, migration and growth [4,5]. Further, the scaffold should resemble native extra cellular matrix (ECM) of the bone in order to support the new tissue formation. In addition, the rapid absorption of plasma proteins will occur initially when the material contacts with the blood. In progress, it would facilitate the platelet surface interaction which might cause the formation of the thrombus. Finally, it results in the failure of the fabricated material [6]. Hence, blood compatibility assessments play a key role in deciding the usage of the fabricated material in clinical applications.

It has been reported that the scaffold based on synthetic and natural polymers was wide spread in tissue engineering application owing to their structural resemblance with the collagen fiber organization in the bone extracellular matrix [7]. There are many techniques utilized for scaffold fabrication such as drawing, self-assembly, phase separation, template synthesis, electrospinning etc., [8]. Among these techniques, the scaffolds based on electrospinning technique was wide spread in biomedical applications especially in tissue engineering application. Electrospinning technique having the ability to produce fine fibers with a diameter ranging from um to nm [9]. The nanofibers attained through electrospinning technique possess desirable characteristics like high surface area with interconnected pores [10,11]. Because of these characteristics, it could able to resemble the ECM matrix of the human tissue. Further, the nanofibers have the ability to support the cell adhesion and proliferation for new tissue generation [12]. The electrospinning has been widely used to electrospun different biodegradable polymers for scaffold fabrication such as poly-l-lactic Acid (PLLA), polycaprolactone (PCL), polyglycolic acid (PGA), polyurethane (PU), polylactic acid (PLA) and poly (lactic-co-glycolic) acid (PLGA). In this research, PU was used to fabricate the nanofibers [13]. PU was selected because it possesses biocompatibility, biodegradability, good barrier properties and better oxidation stability [14,15].

The scaffold used for bone tissue engineering should be bioactive to influence the cellular response and better mechanical strength to support the new tissue growth. Jaganathan et al. electrospun PU scaffold added with different oils namely corn, sunflower, grape seed oil for bone tissue engineering [[16], [17], [18]]. It was observed that the addition of oil enhanced the biocompatibility behaviour of the PU. From these studies, it was evident that the essential oil plays a critical role in enhancing the cellular response. Further, Silva et al. electrospun nanofibrous scaffold based on alginate loaded with magnesium oxide (MgO). It was reported that the addition of magnesium oxide resulted in the enhancement of mechanical strength [19]. Tobías et al. fabricated PLA scaffold incorporated with zinc oxide (ZnO) and showed that the addition of zinc oxide exhibited improvement of the tensile properties. Hence, the addition of metallic particles influenced the mechanical strength [20].

In this research rosemary (RM) oil and copper sulphate (CuSO₄) was selected as key constituents to fabricate the scaffold. Rosemary having botanical name Rosmarinus officinalis L. belongs to the Lamiaceae family which is a perennial shrub that found in several regions of the world. This oil reported having twenty bioactive compounds identified. The main constituents are 44.02% of p-cymene, 20.5% of linalool, 16.62% of g-terpinene, 1.81% of thymol, 3.61% of b-pinene, 2.83% of a-pinene and 2.64% of eucalyptol. The usage of rosemary oil is widely documented in traditional medicine for treating choleretic, colagoguic and also as a pulmonary antiseptic. It has also antidiarrhoic and antirheumatic properties [21]. Few studies had reported the antifungal and antioxidant activity of the rosemary [22]. To improve the mechanical strength of the scaffold, CuSO₄ was added into the electrospun scaffold. Scaffold containing copper particles showed increased antibacterial activity and also non-toxicity to the osteoprogenitor cells. Beyond their excellent antibacterial properties, the copper is reported to influencing the osteoblast activity, bone mineralization and enhancing the osteoblast cell adhesion and proliferation [23]. This study aims to electrospun and decipher the properties of the developed bone scaffold based on polyurethane added with RM and CuSO₄.