Reinforcement of injectable calcium phosphate cement by gelatinized starches

Abstract

Statement of Purpose: Current injectable calcium phosphate bone cements (CPC) encounter the problems of low strength, high brittleness, and low cohesion in aqueous environment, which greatly hinder their clinical applications for loading-bearing bone substitution and minimally invasive orthopedic surgeries like percutaneous vertebroplasty or kyphoplasty. Because of this, many efforts have so far been made to increase CPC mechanical strengths and improve its cohesion and anti-collapsibility (also known as anti-washout property). In this study, a strategy of using food-grade, gelatinized starches to reinforce injectable CPC was proposed. The effects of various starch gels on CPC properties, including injectability, anti-collapsibility, compressive strength and modulus, strain energy density and cytotoxicity, were investigated. Methods: Four types of starches, corn starch, crosslinked starch, cationic starch, and Ca-modified starch were studied. Corn starch, cross-linked starch, cationic starch were purchased and Ca-modified starch gel was prepared by treating the pristine waxy starch with calcium salts like CaCl 2 and Ca(NO 3 ) 2 in the water at the temperature more than 60 o C. Formulation of CPC powder in this study contained 70 wt.% β-tricalcium phosphate, 20 wt.% tetracalcium phosphate and 10 wt.% dicalcium phosphate dehydrate [1]. For preparing starchmodified CPC samples, dry CPC powder was mixed with different types of starch at two contents of 3 wt.% or 10 wt.%. The mixture of dry powders was added to deionized water at liquid-to-solid ratios of 0.75 and 1.05 for the starch contents of 3 wt.% or 10 wt.%, respectively. The starch suspension was then mechanically stirred and gelatinized at 80 o C to form a uniform paste. The CPC/starch pastes were cooled down to room temperature and then injected through a 1 mL syringe with an outlet diameter of 4.8 mm, forming cylindrical paste bars for further testing.Mechanical properties of the starch-modified CPCs were characterized by compression, soaking, and shaking tests. Hardened cement samples were cut into bars of 4.2 mm in diameter and 8.4 mm in length and then dried at 37 o C in air for 2 days. Compression tests were performed on a uniaxial mechanical tester operating at crosshead speed of 1mm/min. For evaluating anti-collapsibility, the cement paste was injected into deionized water directly and soaked in the water for 7 days and then moved to an orbital shaker for shaking tests at the speed of 50 rpm for 1 day and then at 100 rpm for another day.Microstructures of the starch-modified CPCs were evaluated by scanning electron microscopy (SEM). Cytotoxicity of the starch-modified CPC was evaluated by measuring proliferation of osteoblasts in the mixture of cement leaching solution and standard cell culture medium.Results: All the four types of starches studied here resulted in the reinforcements of CPC to different extents, including increased compressive strengths and moduli (Figure 1). Specifically, adding 10 wt.% corn starch and 3 wt.% Ca-modified starch leade...

A novel injectable calcium phosphate-based nanocomposite for the augmentation of cannulated pedicle-screw fixation

“…19 Therefore, to our knowledge, this CPN is the first nanocomposite to demonstrate promising potential for the augmentation of pedicle-screw fixation.…”

“…19 Briefly, when the cement started to set, the paste was placed into a 5 mL syringe with a needle of 1.6 mm inner diameter and extruded under a force less than 50 N. The weight percentage of the extruded paste with respect to the total paste was defined as injectability. The test for each cement formulation was repeated three times.…”

“…18,19 The cement was set in a cylindrical stainless-steel mold (6 mm in diameter and 12 mm in length), and the end planes of cement bars were smoothed with 800-grade sandpaper. The cement bars were then uniaxially compressed by a mechanical tester (HY-1080; Heng Yi Precision Instrument, Shanghai, China) with a 10 kN load cell (gauge precision 0.5 N) at a crosshead speed of 0.5 mm/ min.…”

“…Our previous work has reported the effect of a starch network on improving the mechanical strengths of calcium phosphate cement (CPC). 18,19 The hypothesis here is that this CPN may possess similar biomechanical properties to the clinically used PMMA for application in cannulated pedicle-screw augmentation. Also, its superior biodegradability to PMMA may lower the risk of screw-associated complications, such as infection and difficulty in removing screws.…”

Bioinspired Mechano‐Sensitive Macroporous Ceramic Sponge for Logical Drug and Cell Delivery

“…properties, agreeing to what has reported in the non-porous HA/starch system. [37] Static mechanical properties of CCS can be adjusted dramatically as the moisture in the sponge changes (Figure 2a,b) and its compressive modulus decreases exponentially to the range of kilopascal when the moisture increases to 35 wt%. This adjustability enables CCS to match the compliance of target tissues, which has been a persistent drawback of ceramic-based 3D scaffolds in the applications of controlled release and tissue regeneration.…”