Biodegradable Xylitol‐Based Polymers

Abstract

Synthetic biodegradable polymers have made a considerable impact in various fields of biomedical engineering, such as drug delivery and tissue engineering. The design of synthetic biodegradable polymers for bioengineering purposes is challenging because of the application-specific constraints on the physical properties, including mechanical compliance and degradation rates, and the need for biocompatibility and low cytotoxicity.[1] The monomer selection frequently limits the range of required material properties. Our goal was to design a class of synthetic biopolymers based on a monomer that possesses a wide range of properties that are biologically relevant. This monomer ideally should be: (1) multifunctional to allow the formation of randomly crosslinked networks and a wide range of crosslinking densities; (2) nontoxic; (3) endogenous to the human metabolic system; (4) FDA approved; and (5) preferably inexpensive. We chose xylitol as it meets these criteria. We hypothesized that biodegradable polyesters could be obtained through copolymerization reactions with polycarboxylic acids; the hydration of such biodegradable polymers could be controlled by tuning the different compositions and stoichiometry of the reacting monomer. Here, we describe xylitol-based polymers that realize this design. Polycondensation of xylitol with watersoluble citric acid yielded biodegradable, water-soluble polymers. Acrylation of this polymer resulted in an elastomeric photocrosslinkable hydrogel. Polycondensation of xylitol with the water-insoluble sebacic acid monomer produced tough, biodegradable elastomers with tunable mechanical and degradation properties. These xylitol-based polymers exhibited excellent in vitro and in vivo biocompatibility compared to the well-characterized poly(L-lactic-co-glycolic acid) (PLGA), and are promising biomaterials. Sebacic acid (a metabolite in the oxidation of fatty acids) and citric acid (a metabolite in the Krebs cycle) were chosen as the reacting monomers for their proven biocompatibility; [2,3] they are also FDA-approved compounds. Polycondensation of xylitol with sebacic acid produced water-insoluble waxy prepolymers (termed PXS prepolymers). PXS prepolymers with a monomer ratio of xylitol: sebacic acid of 1:1 and 1:2 were synthesized and had a weight-average molecular weight (M w ) of 2443 g/mol (M n ¼ 1268 g/mol, polydispersity index (PDI) 1.9) and 6202 g/mol (M n ¼ 2255 g/mol, PDI 2.7), respectively. The PXS prepolymers were melted into the desired form and cured by polycondensation (120 8C, 40 m Torr for 4 days, 1 Torr ¼ 133.3 Pa) to yield low-modulus (PXS 1:1) and high-modulus (PXS 1:2) elastomers. PXS prepolymers are soluble in ethanol, dimethyl sulfoxide, tetrahydrofuran and acetone, which allows processing into more complex geometries. Polycondensation of xylitol with citric acid resulted in a water-soluble prepolymer (designated PXC prepolymer), of which the M w was 298 066 g/mol and the M n was 22 305 g/mol (PDI 13.4), compared to linear poly(ethylene glycol) (PEG) standards. To cro...

Influence of Glutamic Acid on the Properties of Poly(xylitol glutamate sebacate) Bioelastomer

“…Therefore, the larger amount of acid can increase the content of the branched structure, which leads to a decrease of T g . Compared with data in the literature [14], T g s of PXGS 1:1-5% (2.4 °C ) and 1:2-5% (−5.5 °C ) were much lower than those of PXS 1:1 (7.4 °C ) and 1:2 (22.9 °C ) at the same acid/xylitol ratio. In addition, the T g was further decreased on increasing the feeding amount of Boc-L-glutamic acid (Figure 4).…”

“…It was obvious that the water contact angle of PXS and PXGS was lower than 90°, which indicated that the bioelastomers showed hydrophilicity. The water contact angle of PXS found in this work was higher than that of Langer's results [14]. At the same ratio of acid/xylitol, the contact angle values of PXGS were lower than these of PXS, and further decreased on increasing the content of Boc-L-glutamic acid (Figure 7).…”

“…Lately, poly(xylitol sebacate) (PXS) elastomers have been successfully fabricated by polycondensation of xylitol and sebacic acid [14,15]. PXS elastomers are composed of nontoxic monomers endogenous to the mammalian organism, and exhibit excellent properties.…”

Mechanical properties and degradation studies of poly(mannitol sebacate)/cellulose nanocrystals nanocomposites

“…The PMS 1 : 1 with a low degree of crosslinking had average UTS of 1.2 AE 0.7 MPa and a Young's modulus of 1.8 AE 0.3 MPa, while for the high crosslinking degree these values increase to 7.0 AE 0.6 MPa and 54.4 AE 3.3 MPa, respectively. While doubling the feed ratio of the sebacic acid monomer, the crosslink density increased 30 and for low degree of crosslinking samples a four-fold enhancement in UTS (4.5 AE 0.7 MPa) and Young's modulus (7.2 AE 0.1 MPa) values were obtained compared with 1 : 1 stoichiometry. Elongation at break of these samples (low crosslinking degree) is also hardly affected by changing stoichiometry to 1 : 2 ratio being reduced by half.…”

A comparative study on poly(xylitol sebacate) and poly(glycerol sebacate): mechanical properties, biodegradation and cytocompatibility

“…According to previously published methods [7,8,30], PGS and poly(xylitol sebacate) (PXS) can be synthesized in two steps. A pre-polymer was first synthesized by polycondensation of an 1:1 molar ratio of either glycerol or xylitol (purity 99%) mixed with sebacic acid (purity 99%).…”