Eggshells will be used for Bone Implant - Seeker's Thoughts

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Eggshells will be used for Bone Implant

In modern medicine, missing and damaged bones are replaced with bone from either the patient or a donor or by using artificial materials containing calcium, such as plaster of Paris, and more recently, phosphate compounds like hydroxyapatite and calcium phosphate, which are produced by using harmful chemicals.



The researchers from Indian Institute of Technology Hyderabad (IIT-H) and National Institute of Technology, Jalandhar developed bone implant material using eggshells, thereby paving way of non-toxic and inexpensive process of developing bone substitutes.

Bone tissue, unlike most of the body’s tissue, has the remarkable ability to regenerate itself, if a fractured bone can be held together it can regenerate the tissue and regain most of its original strength. For severe fracture, bones plates are surgically implanted to hold the bone in place.

When designing bone plates design, material selection, and biocompatibility are the three important considerations. The bone plate must be strong enough to support the load normally placed on the bone while the bone heals.

The plate must also have a stiffness similar to that of the vine to which it is attached. The implant must be non-toxic and cannot cause an inflammatory response in the body.

The stiffness of the bone plate is important because the stress shielding will increase with difference in stiffness.


What is stress shielding?
The stress shielding is the phenomenon in which the implant bears most of the load normally places in the bone. Although this is favourable while the bone is weak, as the bone heals and regain strength, if the bone plate does not allow the bone to carry an increasing load, there will be reduction of bone mass and final regained strength.

What material has usually used for a bone implant?

From the beginning of their use, the material selection was the limiting factor to their success. As technology advanced so did the materials.




Metals

Irons and steel were the most widely employed material in the 1920s. It was their tensile strength that made iron and steel attractive. 
They dissolved rapidly and provoked erosion of adjacent bone. From the standpoint of erosion, biocompatibility and fatigue life, however, stainless steel is inferior to other superalloys.
Copper and nickel discolored bone in which they were embedded. Gold, silver and pure aluminum of not produce discoloration but are too weak and soft for this process chromium-nickel stainless steel was more corrosion resistant in body fluid than other metals.

By 1930, titanium was being used. Its lightness is good mechanochemical properties are important features for the bone implant. The strength of the titanium alloys is lower to equal to that of stainless steel, but its specific strength (strength per density) is far greater than other allows.

Other materials

Hydroxyapatite

Poly (lactic acid) (PLA)

Polycaprolactone – (PCL)




Hydroxyapatite, Ca10 (PO4)6(OH) 2, is a form of calcium phosphate. This ceramic material is used for bone implants and drug delivery system. In each application geometry, dimension, density, pore size, mechanical strength, purity, and chemical phase are important parameters to consider. (www.hydroxyapatite.com3).

 Hydroxyapatite is also the mineral component of natural hard tissues. When it is added to or coated on any candidate implant material, hydroxyapatite forms a composite which is inherently biocompatible and stimulates bone growth at the interface between the hydroxyapatite and the bone.

 When added to a polymer matrix, in particular, hydroxyapatite strengthens the material as a whole, often raising the tensile strength to within the range of cortical bone.




Poly (lactic acid) – (PLA)

Polylactic acid (PLA), a stereoisomer, which is considered to have the best overall properties of the known bioresorbable polymers. Compares PLA with other materials. Its degradation time is the longest, ensuring that a PLA implant will support a bone for the duration of healing. 

Most degradation tests have been performed in vitro, and exact degradation times vary greatly, from 6 weeks to several years. It is only possible the say that the degradation time of PLA is longer relative to other polymers. PLA is also the only polymeric material that allows osseous ingrowth (i.e. new bone formation) to occur while the implant is degrading.



Polycaprolactone – (PCL)

Like PLA and PGA, polycaprolactone (PCL) is a bioresorbable polymer belonging to the group of aliphatic polyesters. It is semi crystalline and has a low melting point of approximately 60C. When synthesized by a ring-opening polymerization, PCL tends to be high-molecular-weight; direct polycondensation produces low-molecular-weight PCL.

 The PCL we have purchased from Polysciences has a molecular weight of approximately 120000 g/mol. In general, lower molecular weight results in higher degradation rate, but higher molecular weight increases strength.


How this new eggshell material will work?

Through this process bone substitute materials such as tricalcium phosphate, a commonly-used bone substitute material can be produced from natural sources.

Pure and thermally stable tricalcium phosphate Nanopowder (powder a hundred thousand times smaller than the sixth of a single human hair) was synthesized from eggshells. It was obtained by using the milling process called ‘ball milling’ to produce these activated calcium phosphate powders.



But why Eggshells?

They are made of largely of minerals (95.1%) including calcium along with small amounts of proteins and water. Calcium is the main mineral component of bone substitute materials.

How it will be beneficial?

Eggshell waste can help to replace commercially available tricalcium phosphate (produced by using harmful chemicals) and has the capability to develop implantable biomaterial for tissue regeneration.



Moreover, eggshells are inexpensive and can be obtained in unlimited quantities. Nioceramics made from eggshells exhibit greater biocompatibility than other synthetic powders due to the presence of additional bioactive elemental ions.

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