Solmaz Maleki-Dizaj1, 2, Masumeh Mokhtarpour3, Hemayat Shekaari3, Simin Sharifi*1
Corresponding author:
Simin Sharifi, Dental and Periodontal Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
Email addresses: sharifis@tbzmed.ac.ir, sharifi.ghazi@gmail.com.
Abstract
Ceramic based structures are commonly applied in the regeneration of hard tissues like bone and teeth because of their similar structure as well as great biocompatibility. Hydroxyapatite (HA) has great biocompatibility, bioactivity and, bio-resorbability, so it is utilized in the repair of injured bone or tooth. Gelatin possesses great emulsifying properties, film-forming features, and excellent water-binding capacity. These properties enable extensive applications in many fields, such as biomedical materials, food, pharmaceutical, and cosmetic industries. HA-gelatin nanocomposite films were prepared and investigated in this study. The results showed relatively monodisperse HA nanoparticles with a mean particle size of 298.40 nm that were mainly pseudo-sphere in morphology. The results also showed the negative values of the zeta potential for the HA nanoparticles (-3.06 mv) and HA-gelatin nanocomposite films (-5.96 mv). The obtained physicochemical properties for the prepared structures suggested them as promising materials in bone-related drug delivery systems or in bone and teeth tissue engineering.
Keywords: Hydroxyapatite; Nanocomposite films; Gelatin; Nanoparticle.
Bone-related disorders are the most important problem in modern orthopedic operations due to improved lifestyle, accidental injuries, and trauma in people of all ages. Ceramics with calcium phosphates base structures are commonly utilized in the regeneration of hard tissue as orthopedic implant alternative because of its similar morphology, chemical composition, crystallinity and size to inorganic component of bone and great biocompatibility [1-6].
Hydroxyapatite (HA) [Ca10 (PO4)6(OH) 2] has great biocompatibility, bioactivity and bio-resorbability, so it is utilized in the repair of injured bone or tooth [7]. Another important component of bone is collagen which contributes up to 89 % and 32 % of the organic matrix and the volumetric composition of bone, respectively [8]. HA has displayed great potential for several applications, for example, catalyst in gas sensor and chromatography for purification of water, manufacturing of fertilizer and as a potential agent for drug delivery [9, 10].
Gelatin is a composition of protein and polypeptide achieved from different animal body parts, possessing great emulsifying properties, film-forming features, and excellent water-binding capacity. Additionally, gelatin is inexpensive, biodegradable, and highly available. These properties enable its extensive applications in many fields, such as biomedical materials, food, pharmaceutical, and cosmetic industries [11-13]. In the preparation of gelatin-based composite films, the combination of gelatin with chitosan, whey and soy proteins, clay nanocomposite, nanotube, and montmorillonite has been used [14-18].
HA-Gelatin nanocomposites can be prepared by several chemical-processing methods such as hydrothermal, Mechanochemical, chemical co-precipitation, Ultrasonic Assisted Irradiation, Microwave irradiation and sol-gel [19-24]. The products achieved by these procedures are commonly irregular. But, the sol-gel technique produces homogeneous nanoparticles easily as compared to other chemical-processing methods [21]. Gelatin as an organic component controls the seeding of HA (the inorganic component) by electrostatic, geometric and stereochemical complementarities [22, 23]. In this present study, HA-gelatin nanocomposite films were prepared and investigated.
2.1. Materials
The commercial type B bovine skin gelatin and glycerin (analytical grade) were purchased from Sigma aldrich company (Germany), (analytical grade), Hydroxyapatite nanoparticles were prepared from Nano-Bazar company (Iran).
2.2. Methods
2.2.1 Films Preparation
For the preparation of nanocomposite films, gelatin was moderately dissolved in distilled water (5% (w/v)) using a magnetic stirrer. Then, HA nanoparticles were added (5.0% of gelatin (w/w)) into the prepared solution. This addition was accrued in the presence of glycerol (50% of gelatin (w/w)) as a plasticizer. The mixture was stirred at 45◦C for 30 min. Then, the obtained solution was placed into the oven (30 ◦C) for 12 h to get dried films.
2.3. Films Characterization
The dehydrated prepared films were placed in a desiccator with a saturated solution of MgNO3•6H2O at 25 ± 0.5◦C during the examinations.
2.4. Physicochemical characterization
2.4.1. Particle size and morphology
The particle size distribution of the HA nanoparticles on composite films was obtained by a Dynamic Light Scattering (DLS) procedure (Malvern, United Kingdom) at 25 ◦C. Moreover, the surface morphology of HA nanoparticles, as well as nanofilms, were tested using a scanning electron microscopy (SEM). The nanoparticles was sputter-coated with gold before the analysis to reduce the surface charging effects. The test was operated at 3.2 kV voltage and 8 μA beam current.
2.4.2. Zeta potential measurements
Zeta potential of the HA nanoparticles, as well as nanofilms, were measured using zeta-sizer (Malvern, UK) at 25 ◦C. The freshly prepared solutions or suspensions were prepared with distilled water and injected into the capillary cell of zeta-sizer.
Particle size distributions of the HA nanoparticles with the mean particle size of 298.40 nm is shown in Figure 1. The particle size distribution was relatively monodisperse with the polydispersity index (PDI) values of 0.342. The SEM image of these nanoparticles is also shown in Figure 2. The image shows that the morphology of the nanoparticles is mainly pseudo-sphere with some needle-like particles. The particle size distribution is seen from the DLS were higher than the size detected by the SEM. Itcould be owing to the viscosity magnitudes (from Stokes-Einstein equation) in DLS technique [25]. Other examiners have obtained similar outcomes for HA-gelatin-silica composite pastes [26].
Morphology of nanoparticles has been stated to display a major effect on cell proliferation, migration, and differentiation. Besides, autophagy activation of cells has been reported to be related to nanoparticle-mediated osteogenic differentiation [27]. SEM imaging of HA-gelatin nanocomposite films is also shown in Figure 4. The image showed that the HA-gelatin nanocomposite is dispersed in the matrix of gelatin films. Yang et al reported that the sphere morphology of nanoparticles improved the osteogenic potential by helping cellular uptake and autophagy activation. They also reported that a polymeric platform that enables the nanoparticles to regenerate bone [27].
Zeta potential gives information on the surface charge and predicting the stability of the colloidal systems. This parameter also may use for the determination of the interaction of colloidal systems with the biological environment [28].
Figures 3 and 5 show the the zeta potential for the HA nanoparticles (-3.06 mv) and HA- gelatin nanocomposite films (-5.96 mv). It has been suggested that negative amounts of the zeta potential have a vital promising outcome on the attachment and proliferation of the bone cells [29]. Many studies on the zeta potential of artificial bio-ceramics like HA and other calcium derivatives have showed that a negative zeta potential improves the in vivo biological properties [29-31]. According to reports, a material with negative zeta potential is more accessible for the attachment and proliferation of osteoblasts than neutral or positive surfaces [31]. The zeta potential (ζ) of ±15 mV is naturally mentioned as the edge for the colloidal system’s stability [25]. Therefore, for both HA nanoparticles and HA-gelatin nanocomposites, the zeta potential was measured in the −20 < ζ < 15 mV range, showing low colloidal stability. This can be improved using surfactants.
Figure 1. The particle size distribution of the HA nanoparticles with the mean particle size of 298.40 nm and PDI of 0.342.
Figure 2. SEM imaging of the HA nanoparticles
Figure 3. Zeta potential of the HA nanoparticles with the zeta potential of -3.06 mv.
Figure 4. SEM imaging of HA-gelatin nanocomposite films.
Figure 5. Zeta potential of HA-gelatin nanocomposite films with the amount of -5.96 mv.
HA-gelatin nanocomposite films were prepared and studied in the current project. The results displayed relatively monodisperse HA nanoparticles with the mean particle size of 291.30 nm that were mainly pseudo-sphere in morphology and negative in surface charge. The obtained physicochemical properties for the prepared structures suggested them as promising materials in bone-related drug delivery systems or in bone and teeth tissue engineering.
Acknowledgments
The financial support from the vice-chancellor for research of Tabriz University of Medical Sciences (under the grant No.61500) is greatly acknowledged.
Conflict of interest
The authors state that they have no conflict of interest.
References
HOW TO CITE
Maleki Dizaj, S., Mokhtarpour, M., Shekaari, H., & Sharifi, S. (2019). Hydroxyapatite-gelatin nanocomposite films; production and evaluation of the physicochemical properties. Journal of Advanced Chemical and Pharmaceutical Materials (JACPM), 2(2), 111-115. Retrieved from http://advchempharm.ir/journal/index.php/JACPM/article/view/70
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