Hydroxyapatite is brittle and it's not suitable for load bearing applications. Other than biphase or triphase calcium phosphate, changing conventional sintering to microwave sintering, is there anything else I can do to improve the hap without making it into a composite material?
Well as far as I know HA is brittle and you can not use it as such for Bone tissue engineering.
But in literature it has been reported that you can do coating of HA on ductile (load bearing) substrate to have improved osteoconduction and osteointegration.
But in my opinion it is impossible to use HA for bone replacements without making in changes in its the chemical composition.
HAP can be mixed with suitable polymer and there are different methods to convert it to scaffolds for non-load bearing application. freeze thaw method is among one to make suitable size scaffolds of your need using mold.
Yes for non load bearing applications you can modify it according to your requirements.
As said by @Arun you can mix it with a polymer or you can do coating of HA on a polymer. But in this case you will have to select a polymer which in service does not emit debries which cause inflamation or some other carcinogenic reactions.
Or if you want to use HA for scaffold applications then you will have to select a biodegradable polymer and can do coating of HA on it.
Actually I find bioceramic is hard to fabricate when it comes in very big size (not in scaffold size). I've ever thought of making it with 3DP. yet it is still challenging. Making into a composite/hybrid material can one of the solution i guess.
There are several composites of Hydroxypatite with chitin and chitosan. Chitin is obtained from crab exoskeletons and is supposed to be a very hard material. Composites of HA with Chitin or chitosan could be used for strong load bearing applications.
Hi Sushma Jadalannagari, I read somethig about chitosan earlier last week. It has a lot of good properties, however I am still not so sure about the hybrid performance of chitin, chitosan/HAP in terms of the mechanical strength and its bioactivity. I guess I need further reading. Thanks ^^
using any bone filler ,can not be as strong as the bone itself,but HA coated materials proved to be very good Initiator for quantity of bony three layers callus Formation in midshaft fractures of Long bone ,despite of advantages of composites with or without HA being used so far as osteoconduction,all bony fragments at the site, at least need minimum fixation with micromotion limits
I suggest reading following papers:
- The synergistic effects of lysophosphatidic acid receptor agonists and calcitriol on MG63 osteoblast maturation at titanium and hydroxyapatite surfaces.
Mansell JP, Barbour M, Moore C, Nowghani M, Pabbruwe M, Sjostrom T, Blom AW.
Biomaterials. 2010 Jan;31(2):199-206. doi: 10.1016/j.biomaterials.2009.09.035.
- Lysophosphatidic acid-functionalised titanium as a superior surface for supporting human osteoblast (MG63) maturation.
Mansell JP, Brown J, Knapp JG, Faul CF, Blom AW. Eur Cell Mater. 2012 May 9;23:348-61.
Your question: “Other than biphase or triphase calcium phosphate, changing conventional sintering to microwave sintering, is there anything else I can do to improve the hap without making it into a composite material?” contains the answer. No way. That is why, CaPO4 are used as coatings of metallic or polymeric implants, as well as various types of CaPO4-containing biocomposites are developed. Perhaps, some dopants (i.e., ion-substituted CaPO4), other types of sintering, applying pressure, using self-setting formulations, lack of porosity, etc. might be of a little help but they do not provide the solution. Pure CaPO4 have a ceramic nature and, therefore, they are always brittle. That is why, natural bones, teeth and deer antlers do not consist of CaPO4 alone but represent biocomposites with complicated both composition and structure.
Hi everybody. changing from conventional to microwave sintering has its own challenge. Microwave sintering offers reduction of sintering time, suppress the growth of grain size able to enhance the hardness of the bioceramic. However it requires very high cost for the machine. Sintering with normal home use microwave need some modification to put a thermometer there to validate the temperature. Up to date, i am still finding how the thing work.
fully agree with Sergey... it is a ceramic ... i believe for load bearing application, you have to coat your HAP on titanium or metallic implant ... or go for composite ...
Researchers still try to optimize fracture toughness of HAp, but there is a limited success. Some advantages could be made by reducing average grain size below 100 nm in fully dense ceramics. You can try two-step sintering method.
Recently, a breakthrough was made by fabrication of HAp/graphene composites and processing by SPS (Carbon, 2013). Fracture toughness reached around 4 MPam1/2. Also, there is a new light in mechanics of HAp/Ti composites (Acta Materialia, 2013).
Dear Miodrag J. Lukic
CAN ı have the full name of the literature you mentioned? Is it Acta Biomaterilia?
Also, there is a new light in mechanics of HAp/Ti composites (Acta Materialia, 2013).
Hello Faik,
the full article title is "On the toughness enhancement in hydroxyapatite-based composites" Acta Materialia, Volume 61, Issue 14, August 2013, Pages 5198-5215,
Good to connect with people in the same field.
Regards.
Also a good one is "Synthesis of hydroxyapatite-reduced graphite oxide nanocomposites for biomedical applications: Oriented nucleation and epitaxial growth of hydroxyapatite"
Journal of Materials Chemistry B
Volume 1, Issue 13, 7 April 2013, Pages 1826-1834
Hi everybody, I totally agree it has something to do starting from the synthesizing of powder, enhancement by developing a hybrid powder, or composite material either polymer or metallic materials. All these are coming from the material aspect.
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