A wide variety of nanostructures are used for drug delivery purpose including liposome, polymeric nanostructures, carbon nanostructures, drug based nanostructures and ceramic nanostructures. in recent years, hydroxyapatite (hap) has attracted considerable attraction to be used in bone scaffold as well as drug delivery systems. the present review is a survey of recent works concerning hydroxyapatite as a superior candidate for drug delivery systems.
The present review article focuses on different hap based systems used for drug delivery and is organized in sections that firstly deal with properties of hap makes it appropriate as drug carrier with special emphasize for cancerous parts and bone implanted zones. secondly, different techniques in which hap used as drug carrier are considered. this part contains the various recent studies to expose the benefits for using hap in drug delivery systems and finally the conclusions are mentioned.
Applications of hydroxyapatite in drug delivery
hydroxyapatite is the main organic constituent of bone tissue. among various ceramics hydroxyapatite (hap) has received a great deal of interest for drug delivery applications because of several desirable factors such as excellent biocompatibility, biodegradability, bioresorability, osteogenisis, osteoconductivity and osteoinductivity and low solubility.
the solubility of ha can be controlled through the substitution of different types of ions. moreover, dissolution of ha is a ph-sensitive. it starts to dissolve in low ph medium, which is typically found in cancerous cells. this enables drugs to be delivered to specific targeted cancerous zones.
in addition, recent studies revealed the anticancer properties of hydroxyapatite particles. hap has antiproapoptotic and antiproliferative effects on cancer cells and especially it has affects in metabolic stability of the cancerous cells.
moreover, hap is an appropriate carrier for antibiotics necessary for bone replaced zones.
drugs could be loaded to hap by either in situ or ex-situ methods. in former method specific process should be adopted so that the drug remains unchanged. coprecipitation and micro-emulsion are better suited to be used for in situ drug loading. ex-situ method is loading the drugs on the surface of hap by absorption and consequently the capacity of ex-situ method is much less than in- situ.
the technics of using hap in drug delivery system include the following:
1) loading the drug on the synthesized scaffolds: approximately the 50% of infections acquired in hospitals are associated to implants. incorporation of antibiotics and subsequent local release of it is evidently highly efficient solution for this problem . hydroxyapatite is reputed as superior biodegradable matrix possess excellent biocompatibility and neglect post-surgery implant removal due to complete resorption and also has superior bioactivity in promoting bone regeneration and enhanced osteoconductivity.
2) using the porous powder of hydroxyapatite: porous hap has been developed to mimic the porous architecture of bone and to provide appropriate space for bone ingrowths. the drug delivery systems based on porous hap have advantage of providing constant and continuous drug levels with limited side effects. it also facilitates the local drug delivery and enables the in vivo administration of short half-life drugs.
3) using coated hydroxyapatite: coating the apatite surface with layers able to conjugate to drugs cause the improvement in drug delivery process. some works have been done about liposome-coated hap and this structure introduced as beneficial structure for therapy of bone disease and anticancer applications. in other work hap surface is coated by layers of polyallyamineand sodium alginate and then this structure was used for alendronate(a drug for osteoporosis healing) loading.
4) using hydroxyapatite as coating materials: hap coatings have drawn much attention due to their excellent biocompatibility, non-toxicity, nonimmunogenicity and superior bioactivity. in addition, its positivity charged surface (ca+2) attracting anion pairing interactions and negatively charged groups, po43-, which promote interactions with protonated amines (-nh3+). due to this superior properties of hap coatings, implant integration without bacterial adhesion could be achieved by combination of antibiotics with hap coating.
The use of hap nanoparticles for the development of new drug delivery systems is a rich and active field of research. for that reason, a common platform of knowledge is necessary to be developed. this review contributes to such multidisciplinary approach to enlightening the hap performance in the field of drug delivery systems.
Hydroxyapatite, drug delivery, cancerous cells, implant