Biomed. Eng.-Biomed. Tech. 2019; aop Farnaz Ghorbani, Ali Zamanian* and Melika Sahranavard Mussel-inspired polydopamine-mediated surface modification of freeze-cast poly (ε-caprolactone) scaffolds for bone tissue engineering applications https://doi.org/10.1515/bmt-2019-0061 Received March 9, 2019; accepted September 19, 2019 Abstract: There are many methods used to fabricate the scaffolds for tissue regeneration, among which freeze cast- ing has attracted a great deal of attention due to the capa- bility to create a unidirectional structure. In this study, polycaprolactone (PCL) scaffolds were fabricated by freeze- casting technology in order to create porous microstructure with oriented open-pore channels. To induce biominer- alization, and to improve hydrophilicity and cell interac- tions, mussel-inspired polydopamine (PDA) was coated on the surface of the freeze-cast PCL constructs. Then, the synergistic effects of oriented microstructure and depos- ited layer on efficient reconstruction of injured bone were studied. Microscopic observations demonstrated that, the coated layer did not show any special change in lamellar microstructure of the scaffolds. Water-scaffold interactions were evaluated by contact angle measurements, and they demonstrated strong enhancement in the hydrophilicity of the polymeric scaffolds after PDA coating. Biodegradation ratio and water uptake evaluation confirmed an increase in the measured values after PDA precipitation. The biomin- eralization of the PDA-coated scaffolds was characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). Obtained results confirmed biomineralization of the con- structs after a 28-day immersion in a simulated body fluid (SBF) solution. Mechanical analysis demonstrated higher compressive strength after PDA coating. L929 fibroblast cell viability and attachment illustrated that PDA-coated PCL scaffolds are able to support cell adhesion and proliferation. The increased secretion of alkaline phosphatase (ALP) after culturing osteosarcoma cell lines (MG-63) revealed the ini- tial capability of scaffolds to induce bone regeneration. Therefore, the PDA-coated scaffolds introduce a promising approach for bone tissue engineering application. Keywords: biomineralization; freeze-cast; poly (ε-caprolactone); polydopamine; scaffold; tissue engineering. Introduction Billions of bone fractures happen every year, and most of them are not completely cured. So, the large volume of no-recovered injuries highlights the need for promo- tion of bone treatment strategies. Current bone treatments involve autografting, allografting, tissue engineering, etc. [1]. Limited availability of autograft sources and the risk of disease transmission in allograft cases make bone tissue engineering a promising strategy [2, 3]. Material selection and fabrication methods are important issues in prepa- ration of scaffolds as one of the most important parts of tissue engineering. There are several methods used for fabrication of tissue engineering scaffolds such as freeze drying [4], freeze- casting [5], electrospinning [6], three-dimensional (3D) printing [7], etc. Among the various mentioned methods, freeze-casting has attracted a great deal of attention due to its capability to create unidirectional porous structures and better simulation of natural tissues [8]. In the freeze- casting or ice-templating method, the pores’ direction, size, shape and fraction volume can be controlled. So, the oriented microstructure can be very effective in final prop- erties of the scaffold such as mechanical, physicochemical and biological behavior [9–11]. Accordingly, the unidirec- tional pores of freeze-cast scaffolds improve water absorp- tion and cellular behavior of the construct, as proved in our recent study [12]. In this method, a polymeric solution is transferred to the mold placed on a circular copper rod. The bottom of this rod is placed into a liquid nitrogen tank to supply the temperature required for freezing. Besides, the heater is connected to this rod, and a proportional inte- gral derivative (PID) controller controls the solidification *Corresponding author: Ali Zamanian, Biomaterials Research Group, Department of Nanotechnology and Advanced Materials, Materials and Energy Research Center, Tehran 1516953715, Iran, Tel.: (+98) 912 3211180, Fax: (+98) 263 6201818, E-mail: a-zamanian@merc.ir. https://orcid.org/0000-0002-7012- 7387 Farnaz Ghorbani: Department of Orthopedics, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai, China. https://orcid.org/0000-0001-9271-7874 Melika Sahranavard: Biomaterials Research Group, Department of Nanotechnology and Advanced Materials, Materials and Energy Research Center, Tehran, Iran Brought to you by | Stockholm University Library Authenticated Download Date | 10/29/19 12:08 AM