Zinc-substituted hydroxyapatite: a biomaterial with enhanced bioactivity and antibacterial properties

Abstract

Hydroxyapatite (HA) is a synthetic biomaterial and has been found to promote new bone formation when implanted in a bone defect site. However, its use is often limited due to its slow osteointegration rate and low antibacterial activity, particularly where HA has to be used for long term biomedical applications. This work will describe the synthesis and detailed characterization of zinc-substituted HA (ZnHA) as an alternative biomaterial to HA. ZnHA containing 1.6 wt% Zn was synthesized via a co-precipitation reaction between calcium hydroxide, orthophosphoric acid and zinc nitrate hexahydrate. Single-phase ZnHA particles with a rod-like morphology measuring ~50 nm in length and ~15 nm in width, were obtained and characterized using transmission electron microscopy and X-ray diffraction. The substitution of Zn into HA resulted in a decrease in both the a- and c-axes of the unit cell parameters, thereby causing the HA crystal structure to alter. In vitro cell culture work showed that ZnHA possessed enhanced bioactivity since an increase in the growth of human adipose-derived mesenchymal stem cells along with the bone cell differentiation markers, were observed. In addition, antibacterial work demonstrated that ZnHA exhibited antimicrobial capability since there was a significant decrease in the number of viable Staphylococcus aureus bacteria after in contact with ZnHA.

Fabrication and physicochemical characterization of porous composite microgranules with selenium oxyanions and risedronate sodium for potential applications in bone tumors

“…However, the SeHA pattern has broader reflections than "pure HA", which means fine crystallites and lower crystallinity. 26,30 The average crystallite sizes (in nm), as determined using Scherrer's equation along the a and c crystallographic axes, with unit cell parameters is presented in Table S1. The crystallite size of the SeHA sample is significantly smaller than "pure HA" and amounts to ,10 nm.…”

Characterization, Dissolution, and Solubility of Zn-Substituted Hydroxylapatites [(ZnxCa1−x)5(PO4)3OH] at 25°C

“…Each dissolution was designed by adding 2.0 g of the synthesized Ca-HA or Zn-Ca-HA to 100 mL of HNO 3 solution (pH = 2) or ultrapure water (pH = 5.6) or NaOH solution (pH = 9) in a series of 150 mL polypropylene bottles, which were then capped and soaked in the water bath of 25 ∘ C. From the bottles, 5 mL of the aqueous solutions was sampled at 23 intervals (1,3,6,12,24,48,72, 120, 240, 480, 720, 1080, 1440, 1800, 2160, 2880, 3600, 4320, 5040, 5760, 7200, 7920, and 8640 hours), filtered through a 0.22-m-pore-size filter and stabilized using 0.2% HNO 3 solution. After each sampling, 5 mL of the corresponding HNO 3 solution, ultrapure water, or NaOH solution was added.…”

“…Phosphate apatites form an enormous mineral group due to their huge isomorphic capacity [1,2], which play an important role in many research areas such as biomaterials and environmental science [3][4][5][6][7].…”

“…As the main inorganic constituent of bone and dental enamel of vertebrates, calcium hydroxylapatite (HA) has been broadly used in osteoinductive coatings, bone replacement and repair, dental orthopaedics, and so forth [3,6,[8][9][10][11]. The substitution of trace ions in hydroxylapatite can affect not only its lattice parameters and , crystallinity, and morphology, but also its dissolution mechanism and other physicochemical properties [10][11][12].…”

In vitro evaluation of bioactivity of SiO2-CaO-P2O5-Na2O-CaF2-ZnO glass-ceramics

“…In addition to that it has profound antibacterial properties [9,10]. ZnO increases the tendency towards crystalline phase separation as it decreases the viscosity of glass.…”