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Dissertation - Vrushali Bhagat.pdf (6.07 MB)

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Poly(Ester Urea) Based Biomimetic Bone and Soft Tissue Adhesives

Bhagat, Vrushali
http://rave.ohiolink.edu/etdc/view?acc_num=akron1519919069002674

Abstract Details

2018, Doctor of Philosophy, University of Akron, Polymer Science.
Sutures and staples are an integral part of surgeries and also the gold standard for surgical closure techniques. Additionally, in the case of orthopedic surgeries, metallic implants like plates, pins or screws are usually inserted as bone grafts. However, these techniques are quite invasive in nature, may cause wound dehiscence, secondary tissue damage, microbial infection, poor cosmetic outcome and more importantly discomfort to the patient. In some cases, the patient has to undergo another surgery for removal or replacement of sutures or bone grafts. These shortcomings have led to an urgent need to develop alternative, less invasive surgical closure techniques. Use of tissue adhesives for wound closure is an attractive alternative over the invasive methods owing to ease of preparation and application, strong adhesion and gradual degradation with tissue reconstruction. However, their toxic degradation products and potentially harmful cross-linking strategies have limited their medical applications. Recently, biomimetic adhesives have become a popular choice for application as tissue adhesives. Biomimetic adhesives are inspired from examples of adhesion in nature like mussels, sandcastle worms, barnacles, caddisflies, geckos and spiders to name a few. The adhesion characteristics and adhesive properties of mussels are of particular interest due to their strong wet and reversible adhesion, steadfast hold under variation in temperature, pH and water currents. The mussel adhesive is rich in polyphenolic protein - 3,4-dihydroxyphenylalanine (DOPA). The catechol functionality in DOPA is assumed to be the source of strong underwater adhesion in mussels. In this work, we have synthesized a catechol functionalized ethanol soluble poly(ester urea) (poly(CA-Ser-co-Leu-co-PPG) copolymer for soft tissue application. Incorporation of 20 mol% PPG units in the polymer backbone facilitates ethanol solubility making these adhesives clinically relevant. The polymer was characterized using NMR, IR and UV-VIS spectroscopy to confirm its structure and catechol content. The physical properties of the polymer like Tg, Td, Mn, Mw and ÐM were characterized by DSC, TGA and SEC respectively. The lap shear adhesion strength of this polymer on aluminum adherends was ~ 3.2 ± 0.8 MPa after cross-linking with tetrabutylammonium periodate. On wet porcine skin, the adhesion strength was ~ 10.6 ± 2.1 kPa after 4 h of curing for a catechol:crosslinker = 10:1 with minimal to no toxicity. Moreover, the adhesion strength on wet porcine skin was much stronger than Tisseel – commercial fibrin glue. Caddisflies are aquatic organisms that spin their own adhesive silk underwater to form protective casing, capture prey and for locomotion. Caddisfly adhesive silk is comprised of H-fibroin and L-fibroin in a 1:1 ratio and has abundant divalent cations like Ca2+. The H-fibroin silk is heavily phosphorylated with repeating pSXn units where pS is phosphoserine and X is a more hydrophobic amino acid like valine or isoleucine. The phosphate groups play a role in underwater adhesion in addition to interacting with the divalent cations to impart stiffness and tensile strength to the fiber. Phosphate groups also have a strong electrostatic interaction with the Ca2+ on the bone surface which aids in promoting bone adhesion. To test this hypothesis, we synthesized phosphate functionalized poly(ester urea) – poly(pSer-co-Val) with 2% and 5% phosphate functionality. As confirmed via 1H, 13C, 31P NMR and ATR-IR spectroscopy. The physical properties of the polymers were characterized using DSC, TGA and SEC. The maximum lap shear adhesion strength on an aluminum adherend was 1.17 ± 0.19 MPa and 439 ± 203 kPa on wet bovine bone after cross-linking with Ca2+. The adhesion strength on bovine bone was comparable to the commercially available bone cement. These polymeric mimics are degradable, non-toxic and soluble in a clinically relevant solvent which sets them apart from the commercial options.
Matthew Becker, Dr. (Advisor)
Ali Dhinojwala, Dr. (Committee Chair)
Chrys Wesdemiotis, Dr. (Committee Member)
Mesfin Tsige, Dr. (Committee Member)
Bryan Vogt, Dr. (Committee Member)
196 p.
Polymer Chemistry
Tissue adhesives, Biomimetic, Caddisfly, Mussels, Degradable, Poly ester urea, Catechol, Phosphorylation

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Citations

  • Bhagat, V. (2018). Poly(Ester Urea) Based Biomimetic Bone and Soft Tissue Adhesives [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1519919069002674

    APA Style (7th edition)

  • Bhagat, Vrushali. Poly(Ester Urea) Based Biomimetic Bone and Soft Tissue Adhesives. 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1519919069002674.

    MLA Style (8th edition)

  • Bhagat, Vrushali. "Poly(Ester Urea) Based Biomimetic Bone and Soft Tissue Adhesives." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1519919069002674

    Chicago Manual of Style (17th edition)

akron1519919069002674
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