Advances in Applied NanoBio-Technologies 2020, Volume 1, Issue 1, Pages: 1-4 1 Surface Modification of Nano-Hydroxyapatite by Coating Stearic Acid M. Yousefi 1 *, N. Modghan 2 , M.H. Ebrahimzadeh 2 1 Department of Orthopaedic Surgery, Mashhad University of Medical Sciences, Mashhad, Iran 2 Department of Materials Science and Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran Received: 06/01/2020 Accepted: 13/03/2020 Published: 20/03/2020 Abstract Todays, researchers are challenging with manufacturing polymeric nanocomposites reinforced with ceramic particles due to two inherent properties of ceramic reinforcement particles, particle agglomeration and incompatibility between hydrophilic ceramic particles and hydrophobic polymeric matrix. So in this study, we used nano-Hydroxyapatite (n-HA) as ceramic material and Stearic acid as amphiphilic material for coating n-HA, hydroxysteric acid (SA) surfactant was used for surface coating particles between the hydrophilic HA powders and the hydrophobic polymers. The surface modification and effect of this method were evaluated by by Fourier transformation infrared (FTIR), x-ray diffractometer (XRD), thermal gravimetric analysis (TGA) and Scanning electron microscopy (SEM). The result of FTIR showed that n-HA surfaces were modified successfully and the modification method had the proper grafting amount according to TGA due to this method of modification will be proper for coating reinforcement particles in polymeric matrix. Keywords: Hydroxyapatite, Stearic acid, Hydrophilic ceramic, Amphiphilic, Stearic acid 1 Introduction 1 Aliphatic polyesters, such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA) and their copolymers (PLGA), are biodegradable and essentially non-toxic one of the main polymer groups, such as bone screws, bone plates and pins made of PLA or PDLLA have been widely used in bone fracture fixation [1–3]. However, PLLA and PDLLA have still their weaknesses, for example for PLLA, although it can be completely degraded in one or two years [4], Moreover, for clinical research, and so far it has been one of the most commonly used in biomedical fields such as bone screws, due to the combination of its bioabsorbabtily, biodegradable, biocompatible .[5]. However, for PLLA, there are still some critical subjects to be solved so as to be used as bone screws in body, for example, its mechanical properties are too low to be sufficient for more demanding load application due to its non-crystallinity, and the poor cell attachment ability [6,7]. To overcome these inherent disadvantages, the prevalent method is to introduce the inorganic fillers into PLLA to fabricate filler/polymer composites, such as hydroxyapatite, _-tricalcium phosphate, bioglass, titanium dioxide, and so on [8-11]. Among the inorganic filler/PLLA composites, nano-hydroxyapatite (n-HA) is a major inorganic component of natural bone, so it was thought to have good bioactivity and osteoconductivity properties due to their chemical and structural similarity to the mineral phase of native bone. Moreover, n-HA is a weak alkali inorganic filler, which can buffer acidic in body[12–14]. Therefore, to improve the shortcomings of PLLA, the n-HA/PLGA composite have been Corresponding author: M. Yousefi, Department of Orthopaedic Surgery, Mashhad University of Medical Sciences, Mashhad, Iran. E-mail: yousefi_shiraz@yahoo.com extensively investigated, which are expected to reinforce mechanical properties, improve cell adhesion and endow it with bioactivity as well as adjust the degradation rate by inducing n- HA nanoparticles [15–17]. However, there are two most problematic issues in manufacturing n-HA/PLLA composite, the one is the agglomeration of the HA nanoparticles in the PLLA matrix, and another is a weak adhesion between the hydrophilic n-HA and hydrophobic polymer, which will result in early failure at the interface and thus deteriorate the mechanical properties and limit its load-bearing applications. To solve these problems, it is necessary to hunt for an appropriate modification method for n-HA to improve the dispersion and the compatibility between the filler and the polymer, and it has been becoming the key of research work. Accordingly, many methods have already been applied [18–23], including a diverse class of coupling agents, zirconyl salt, poly acids, dodecyl alcohol, polyethylene glycol and isocyanate, and so on. However, among these techniques, the modification effects were all not very ideal, most of these methods are complex, while the surface of nanoparticles is not well covered, Based on this aim of oure work is to develop a modified coating to potentially enhance the application of nanohydroxyapatite for biomaterials. Therfore n-HA was coated with stearic acid by means of solution mixing, this method is simple and low cost 2 Materials and Methods 2.1 Materials n-HA was prepared on our previous report[24], Briefly, separate solutions of calcium nitrate tetra hydrate (Ca (NO3)2·4H2O; Merck) in water and phosphoric acid (H3PO4; Merck) in ethanol/water (1/4 by mole) were prepared by stirring each for 3 h and were then mixed together at a stoichiometry of [Ca]/[P] ¼ 1.67, followed by stirring for 6 h, and aging for 7 days at room temperature, The product was white precipitated J. Adv. Appl. NanoBio Tech. Journal web link: http://www.AANBT.dormaj.com https://doi.org/10.47277/AANBT/1(1)4