<div>Wounds are created in soft and hard tissue through surgery or disease. As the wound heals, the tissue is held in place using sutures or staples for soft tissue or plates, pins, or screws for hard tissues. These fixation methods inherently damage the surrounding healthy tissue. Surgical adhesives are a non-damaging alternative to these methods. In order to be effective, surgical adhesives must be biocompatible,</div><div>adhere strongly in a moist environment, and have mechanical properties similar to those of the native tissue.</div><div><br></div><div><div>To address the design criteria for surgical adhesives, we look to nature to find inspiration from compounds that provide these properties. Mussels use catechol-based</div><div>molecules to adhere to surfaces in wet and turbulent environments. Incorporating catechols into polymer systems can provide adhesion even in moist biological environments.</div><div>Mimics of elastomeric proteins from soft tissue can be used as backbones for soft and flexible adhesive systems. In particular, elastin-inspired proteins have a well-defined modular sequence that allows for a range of design choices. In this work, we explored the behavior of elastin- and mussel-inspired natural and synthetic polymers in biologically relevant environments.</div></div><div><br></div><div><div>First, the cytocompatibility of a catechol-containing poly(lactic acid) (cPLA) hard tissue adhesive was studied. The cPLA polymer was reacted with iron- or periodatebased</div><div>crosslinkers and compared to PLA. Fibroblasts grown directly on cPLA or cultured with leachate from cPLA had high viability but slower growth than cells on PLA. The periodate crosslinker was significantly cytotoxic, and cells grown on cPLA crosslinked with periodate had reduced metabolism and slowed growth. Cells grown on or in leachate from iron-crosslinked cPLA had similar viability, metabolism, and growth to cells on or in leachate from cPLA. The iron-crosslinked cPLA is a promising</div><div>cytocompatible adhesive for hard tissue applications.</div></div><div><br></div><div><div>Second, two elastin-like proteins (ELP) were developed that had pH-sensitive properties in solution and when crosslinked into hydrogels. Both ELPs had a large number of ionizable tyrosine and lysine residues, and one design also had a large number of ionizable histidine and aspartic acid residues. The stiffness of the hydrogels was maximized at pH values near the isoelectric point of the protein. The stoichometric ratio of crosslinker used affected hydrogel stiffness but did not significantly alter the pH-sensitivity of the gel. The crosslinked gel shrank when swelled at physiological pH. The pH-sensitive mechanical properties of hydrogels made from the two ELPs did not vary significantly. The tyrosine and lysine residues in one ELP were also</div><div>chemically blocked through acetylation to lower the isolectric point of the protein. The acetylated hydrogels had maximum stiffness at a pH near the isoelectric point of the acetylated ELP. The stiffness of both the native and acetylated gels were within the range of soft tissue. Through a combination of crosslinker ratio and chemical modification, the pH-responsive properties of the elastin-inspired hydrogels could be tuned.</div></div><div><br></div><div><div>Finally, adhesive proteins were created that were inspired by both elastin and mussels. An ELP was modified to include catechol groups (mELP). The ELP and mELP were optimized for adhesive use in a soft tissue system. A warm and humid environment was used to study the adhesion of these proteins on pig skin. Iron and (hydroxymethyl) phosphine crosslinkers increased the adhesive strength of both proteins, and periodate increased the adhesive strength of mELP. The adhesive strengths of the proteins were maximized when mELP was mixed with iron or when either protein were mixed with (hydroxymethyl)phosphine crosslinkers. These maximized adhesives were 12-17 times stronger than a commercially available sealant. In addition,</div><div>the iron and mELP adhesive formulation achieved high adhesive strengths even when cured for only ten minutes. This adhesive formula shows promise for adhesive</div><div>applications on soft tissue.</div></div>

Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

<p><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a>ABSTRACT</a></p> <p>Phenols are ubiquitous in our surroundings including biological molecules such as L-Dopa metabolites, food components, such as whiskey and liquid smoke, etc. This dissertation describes a new method for detecting phenols, by reaction with Gibbs reagent to form indophenols, followed by mass spectrometric detection. Unlike the standard Gibbs reaction which uses a colorimetric approach, the use of mass spectrometry allows for simultaneous detection of differently substituted phenols. The procedure is demonstrated to work for a large variety of phenols without <i>para</i>‐substitution. With <i>para</i>‐substituted phenols, Gibbs products are still often observed, but the specific product depends on the substituent. For <i>para</i> groups with high electronegativity, such as methoxy or halogens, the reaction proceeds by displacement of the substituent. For groups with lower electronegativity, such as amino or alkyl groups, Gibbs products are observed that retain the substituent, indicating that the reaction occurs at the <i>ortho</i> or <i>meta</i> position. In mixtures of phenols, the relative intensities of the Gibbs products are proportional to the relative concentrations, and concentrations as low as 1 μmol/L can be detected. The method is applied to the qualitative analysis of commercial liquid smoke, and it is found that hickory and mesquite flavors have significantly different phenolic composition.</p> <p>In the course of this study, we used this technique to quantify major phenol derivatives in commercial products such as liquid smoke (catechol, guaiacol and syringol) and whiskey (<i>o</i>-cresol, guaiacol and syringol) as the phenol derivatives are a significant part of the aroma of foodstuffs and alcoholic beverages. For instance, phenolic compounds are partly responsible for the taste, aroma and the smokiness in Liquid Smokes and Scotch whiskies. </p> <p>In the analysis of Liquid Smokes, we have carried out an analysis of phenols in commercial liquid smoke by using the reaction with Gibbs reagent followed by analysis using electrospray ionization mass spectrometry (ESI-MS). This analysis technique allows us to avoid any separation and/or solvent extraction steps before MS analysis. With this analysis, we are able to determine and compare the phenolic compositions of hickory, mesquite, pecan and apple wood flavors of liquid smoke. </p> <p>In the analysis of phenols in whiskey, we describe the detection of the Gibbs products from the phenols in four different commercial Scotch whiskies by using simple ESI-MS. In addition, by addition of an internal standard, 5,6,7,8-tetrahydro-1-napthol (THN), concentrations of the major phenols in the whiskies are readily obtained. With this analysis we are able to determine and compare the composition of phenols in them and their contribution in the taste, smokey, and aroma to the whiskies.</p> <p>Another important class of phenols are found in biological samples, such as L-Dopa and its metabolites, which are neurotransmitters and play important roles in living systems. In this work, we describe the detection of Gibbs products formed from these neurotransmitters after reaction with Gibbs reagent and analysis by using simple ESI‐MS. This technique would be an alternative method for the detection and simultaneous quantification of these neurotransmitters. </p> <p>Finally, in the course of this work, we found that the positive Gibbs tests are obtained for a wide range of <i>para</i>-substituted phenols, and that, in most cases, substitution occurs by displacement of the <i>para</i>-substituent. In addition, there is generally an additional unique second-phenol-addition product, which conveniently can be used from an analytical perspective to distinguish <i>para</i>-substituted phenols from the unsubstituted versions. In addition to using the methodology for phenol analysis, we are examining the mechanism of indophenol formation, particularly with the <i>para</i>-substituted phenols. </p> <p>The importance of peptides to the scientific world is enormous and, therefore, their structures, properties, and reactivity are exceptionally well-characterized by mass spectrometry and electrospray ionization. In the dipeptide work, we have used mass spectrometry to examine the dissociation of dipeptides of phenylalanine (Phe), containing sulfonated tag as a charge carrier (Phe*), proline (Pro) to investigate their gas phase dissociation. The presence of sulfonated tag (SO₃^-) on the Phe amino acid serves as the charge carrier such that the dipeptide backbone has a canonical structure and is not protonated. Phe-Pro dipeptide and their derivatives were synthesized and analyzed by LCQ-Deca mass spectroscopy to get the fragmentation mechanism. To confirm that fragmentation path, we also synthesized dikitopeparazines and oxazolines from all combinations of the dipeptides. All these analyses were confirmed by isotopic labeling experiments and determination and optimization of structures were carried out using theoretical calculation. We have found that the fragmentation of Phe*Pro and ProPhe* dipeptides form sequence specific b₂ ions. In addition, not only is the ‘mobile proton’ involved in the dissociation process, but also is the ‘backbone hydrogen’ is involved in forming b₂ ions. </p> <p> </p>