RESUMO
Marine mussels secrete proteins rich in residues containing catechols and cationic amines that displace hydration layers and adhere to charged surfaces under water via a cooperative binding effect known as catechol-cation synergy. Mussel-inspired adhesives containing paired catechol and cationic functionalities are a promising class of materials for biomedical applications, but few studies address the molecular adhesion mechanism(s) of these materials. To determine whether intramolecular adjacency of these functionalities is necessary for robust adhesion, a suite of siderophore analog surface primers was synthesized with systematic variations in intramolecular spacing between catechol and cationic functionalities. Adhesion measurements conducted with a surface forces apparatus (SFA) allow adhesive failure to be distinguished from cohesive failure and show that the failure mode depends critically on the siderophore analog adsorption density. The adhesion of these molecules to muscovite mica in an aqueous electrolyte solution demonstrates that direct intramolecular adjacency of catechol and cationic functionalities is not necessary for synergistic binding. However, we show that increasing the catechol-cation spacing by incorporating nonbinding domains results in decreased adhesion, which we attribute to a decrease in the density of catechol functionalities. A mechanism for catechol-cation synergy is proposed based on electrostatically driven adsorption and subsequent binding of catechol functionalities. This work should guide the design of new adhesives for binding to charged surfaces in saline environments.
RESUMO
BACKGROUND: Health care in America continues to place more importance on providing value-based medicine. Medicare reimbursements are increasingly being tied to this and future policy changes are expected to reinforce these trends. Recent literature has shown pediatric femur fractures in preschool-age children have equivalent clinical and radiographic outcomes when treated with spica casting or flexible intramedullary nails (IMN). We compared hospital care statistics including charges for nonoperative versus operative treatment for closed femur fractures in 3- to 6-year-olds. METHODS: An IRB-approved retrospective chart review was performed of 73 consecutive 3- to 6-year-olds treated at a regional level 1 pediatric hospital from January 1, 2009 to December 31, 2013 with an isolated, closed femoral shaft fracture. Exclusion criteria included open fractures, bilateral injury, and polytrauma. Immediate spica casting was performed in the Emergency Department or Anesthesia Procedure Unit versus IMN in the operating room. RESULTS: A total of 41 patients were treated with spica casting and 32 patients were treated operatively with flexible IMNs; 3 patients failed nonoperative care. After analysis of final treatment groups, significant differences included age at injury: 3.7 years for cast versus 5.3 years for IMN (P<0.001), time to discharge 21 versus 41 hours (P<0.001), 3.2 versus 4.4 clinic visits (P<0.001), follow-up 3.5 versus 9.4 months (P<0.001). Orthopedic surgeon charges were $1500 for casted patients versus $5500 for IMN (P<0.001). Total hospital charges were $19,200 for cast versus $59,700 for IMN (P<0.001). No difference was found between clinic charges or number of radiographs between groups. In total, 76% of cast group were discharged <24 hours from admission versus 8.6% in operative group. In the operative group, 83% had implant removal with no statistically significant charge difference between those who had implant removal versus retention. CONCLUSIONS: Treatment of pediatric femur fractures in 3- to 6-year-olds with IMN is associated with longer hospital stays, significantly greater hospital charges, longer follow-up and more clinic visits compared with spica casting. These findings are at odds with previous literature showing shorter hospital stays and decreased cost with nailing compared to traction and casting. This shows a clear difference between 2 treatments that yield similar clinical and radiographic outcomes. LEVEL OF EVIDENCE: Level III-retrospective comparative study.