Molecular Interactions between Amino Silane Adhesion Promoter and Acrylic Polymer Adhesive at Buried Silica Interfaces.

In this study, the influence of an amino silane (3-(2-aminoethylamino)-propyldimethoxymethylsilane, AEAPS) on the interfacial structure and adhesion of butyl acrylate/methyl methacrylate copolymers (BAMMAs) to silica was investigated by sum frequency generation vibrational spectroscopy (SFG). Small amounts of methacrylic acid, MAA, were included in the BAMMA polymerizations to assess the impact of carboxylic acid functionality on the glass interface. SFG was used to probe the O-H and C═O groups of incorporated MAA, ester C═O groups of BAMMA, and CH groups from all species at the silica interfaces. The addition of AEAPS resulted in a significant change in the molecular structure of the polymer at the buried interface with silica due to specific interactions between the BAMMA polymers and silane. SFG results were consistent with the formation of ionic bonds between the primary and secondary amines of the AEAPS tail group and the MAA component of the polymer, as evidenced by the loss of the MAA O-H and C═O signals at the interface. It is extensively reported in the literature that methoxy head groups of an amino silane chemically bind to the silanols of glass, leaving the amine groups available to react with various chemical functionalities. Our results are consistent with this scenario and support an adhesion promotion mechanism of amino silane with various aspects: (1) the ionic bond formation between the tail amine group and acid functionality on BAMMA, (2) the chemical coupling between the silane head group and glass, (3) migration of more ester C═O groups to the interface with order, and (4) disordering or reduced levels of CH groups at the interface. These results are important for better understanding of the mechanisms and effect of amino silanes on the adhesion between acrylate polymers and glass substrates in a variety of applications.

Observing a Chemical Reaction at a Buried Solid/Solid Interface in Situ.

Chemical reactions are the most important phenomena in chemistry. However, chemical reactions at buried solid/solid interfaces are very difficult to study in situ. In this research, the chemical reaction between two solid polymer materials, a nylon film and a maleic anhydride (MAH) grafted poly(ethylene-octene) (MAHgEO) sample, was directly analyzed at the buried nylon/MAHgEO interface at the molecular level in real time and in situ, using surface and interface sensitive sum-frequency generation (SFG) vibrational spectroscopy. Disappearance of nylon signals indicated a chemical reaction between amine and hydrolyzed amide groups of nylon and MAH groups on the MAHgEO at the buried interface. The appearance of SFG signals from reaction products was also observed at the buried nylon/MAHgEO interface. The mechanism of the observed interfacial reaction was further analyzed. Temperature-dependent SFG experiments were performed to measure the activation energy of the interfacial reaction, enabling a comparison with that reported for the bulk materials. The interfacial chemical reaction between nylon and MAHgEO greatly improved the adhesion of these dissimilar materials. The detailed analysis of a chemical reaction between two polymers at the polymer/polymer buried interface underscores the utility of SFG as a powerful analytical tool to build understanding of buried interfaces and to accelerate the design of interfacial structures with desired properties.

Probing Molecular Behavior of Carbonyl Groups at Buried Nylon/Polyolefin Interfaces in Situ.

Nylon and maleic anhydride (MAH)-grafted polyolefin-based thin co-extruded multilayer films are widely used in packaging applications encountered in daily life. The molecular structure of the nylon/MAH-grafted polyolefin buried interface and molecular bonding between these two chemically dissimilar layers are thought to play an important role in achieving packaging structures with good adhesion. Here, the molecular bonds present at a nylon/maleic anhydride (MAH)-grafted polyethylene buried interface were systematically examined in situ for the first time using sum frequency generation (SFG) vibrational spectroscopy. The carbonyl stretching frequency region of the SFG spectra of a nylon/MAH-grafted polyethylene buried interface showed the presence of hydrolyzed MAH groups grafted to the polyethylene chain and very low levels of unreacted MAH enriched at the buried interface. The ability of SFG to detect these molecular species at the buried interface yields important understanding of the interfacial molecular structure and provides the basis for subsequent in situ studies of the bonding reaction between the grafted MAH and nylon directly at the interface. This understanding may guide the design of multilayer films with improved properties such as enhanced adhesion between polymer layers. The approach used in this study is general and is applicable to study the molecular characteristics of other buried interfaces of significance, such as buried interfaces involving polymers in solar cells, polymer semiconductors, and batteries. Nylon impact modification is another area of interest where the interaction between the MAH-grafted elastomer and the continuous phase of nylon is important.

Plasma treatment effect on polymer buried interfacial structure and property.

Adhesion is important in many industrial applications including those in the microelectronics industry. Flip-chip assemblies commonly utilize epoxy underfills to promote reliability and the buried interfacial structure of underfills is crucial to device lifetime. Poor adhesion at this interface can cause premature device failure. One method to increase adhesion strength is to plasma treat the substrate attached to underfills, however, the mechanism of this increase in adhesion strength has not been thoroughly investigated at the molecular level in situ, because it is difficult to probe a buried interface where the adhesion occurs. In this work, sum frequency generation (SFG) vibrational spectroscopy was utilized to investigate the buried polymer/epoxy resin interface at the molecular level. Plasma treatment was performed on the polymer surfaces and the effects were examined. The buried interfaces between the polymer surface before and after plasma treatment and epoxy were then investigated to understand if the effects of the treatment can be observed using SFG. It was found that the molecular structure of the buried interface of the pristine polymer surface in contact with epoxy is drastically different from the buried interface of the plasma treated surface with epoxy. The buried interface containing the plasma treated polymer surface was found to be considerably more disordered and had much higher adhesion strength. This research elucidates the plasma treatment effects on structures and properties of buried polymer/epoxy interfaces, providing in-depth understanding on the mechanism of adhesion strength increase facilitated by plasma treatment.

Delayed Abdominal Flap for Upper Extremity Soft Tissue Coverage.

Unlike other body parts, the upper extremity has critical structures close to the skin, making soft tissue injuries more complex. These injuries can result from various causes, including trauma and necrotizing soft tissue infections, necessitating reconstruction. Historically, pedicled flaps from the groin and abdomen were commonly used for upper extremity reconstruction, but they had limitations, such as the need for flap division and debulking, patient discomfort, and stiffness. Free flap reconstruction has become the preferred method, but it still faces challenges like patient and facility issues, the absence of recipient vessels after injury, and multi-surface wounds. This case report describes a 67-year-old patient with a severe necrotizing soft tissue infection in the right upper extremity. After multiple debridement procedures, the patient underwent hand amputation and soft tissue coverage using an abdominal wall-based flap. The objectives of achieving stable soft tissue coverage while preserving maximal length of the upper extremity were successfully achieved, and the patient expressed satisfaction with the outcomes. Inadequate management of upper extremity wounds can lead to amputation and psychological distress. The reconstructive ladder is used to approach upper extremity soft tissue defects, with free tissue transfer being the standard for larger defects. However, abdominal flaps still have indications when free tissue transfer is not feasible or contraindicated. It is imperative that plastic surgeons have these techniques in their armamentarium to provide a service to the ever more complex patient with an upper extremity wound.

Cerebral desaturation during shoulder arthroscopy: a prospective observational study.

BACKGROUND: Patients undergoing arthroscopic shoulder surgery in the beach chair position may be at increased risk for serious neurocognitive complications as a result of cerebral ischemia. QUESTIONS/PURPOSES: We sought to define the (1) incidence; (2) timing; and (3) magnitude of intraoperative cerebral desaturation events (CDEs) in subjects undergoing arthroscopic shoulder surgery in the beach chair position, as well as whether (4) the length of surgery was an independent risk factor for intraoperative CDEs. METHODS: Regional cerebral tissue oxygen saturation (rSO2) was monitored intraoperatively using near-infrared spectroscopy on 51 consecutive patients undergoing arthroscopic shoulder surgery in the beach chair position. Intraoperative decreases in rSO2 of 20% or greater were defined as CDEs. RESULTS: The incidence of intraoperative CDEs in our series was 18% (nine of 51). Among the patients demonstrating CDE (n = 9), the mean time to onset of initial CDE was 18 minutes 38 seconds postinduction. Of those experiencing CDEs, the mean maximal decrease in rSO2 was 32% from preoperative baseline per patient. Additionally, the mean number of separate CDE instances was 1.89 in this patient population with an average duration of 3 minutes 3 seconds per instance. There was no statistically significant difference (p = 0.202) between patients demonstrating CDEs and those without in regard to length of surgery (95 versus 88 minutes). CONCLUSIONS: The degree and duration of cerebral ischemia required to produce neurocognitive dysfunction in this patient population remains undefined; however, cerebral oximetry with near-infrared spectroscopy allows prompt identification and treatment of decreased cerebral perfusion. We believe protocols aimed at detecting and reversing CDE may improve patient safety.

Modified Frailty Index is an Independent Predictor of Death in the Burn Population: A Secondary Analysis of the Transfusion Requirement in Burn Care Evaluation (TRIBE) Study.

Frailty can increase the risk of dying after suffering a severe injury. The Modified Frailty Index (MFI) was developed by the American College of Surgeons National Surgical Quality Improvement Program to determine the impact of frailty on outcomes. Our aim was to correlate frailty with survival following a burn injury using the 11-item and 5-item MFI. We performed a secondary analysis of the Transfusion Requirement in Burn Care Evaluation (TRIBE) study. Data including, age, gender, medical history, extent and severity of burn injury, inhalation injury and discharge disposition was collected from the TRIBE database. The 11-item MFI (MFI-11) and 5-item MFI (MFI-5) scores were calculated for all patients in the TRIBE database. The TRIBE database included 347 patients. The mean age of subjects was 43 ± 17 years. Mean total body surface area burn (TBSA) was 38 ± 18%, and 23% had inhalation injury. Multivariate logistic regression analysis determined that both MFI-5 (OR 1.86; 95% CI: 1.11-3.11; P-value .02) and MFI-11 (OR 1.83; 95% CI: 1.18-2.8; P-value .007) were independent predictors for mortality. Additionally, MFI-11 scores that are >1 were independently associated with a markedly increased risk of dying after a burn injury (OR 2.91; 95% CI: 1.1-7.7; P-value .03). The MFI can be used to identify vulnerable burn injured patients who are at high risk of dying.

Nitric oxide releasing poly(vinylidene fluoride-co-hexafluoropropylene) films using a fluorinated nitric oxide donor to greatly decrease chemical leaching.

Nitric oxide (NO) releasing polymers have been widely applied as biomaterials for a variety of biomedical implants and devices. However, the chemical leaching of NO donors and their byproduct species is almost always observed during the application of polymers doped with NO donors, unless the donor is covalently linked to the polymer. Herein, we report the first NO releasing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fluorinated copolymer prepared by incorporating a fluorinated S-nitrosothiol as the NO donor. Under physiological conditions, the resulting polymeric films can release NO for 16 days. Importantly, due to both fluorine-fluorine and electrostatic charge interactions between the fluorinated NO donor and the PVDF-HFP copolymer, the total chemical leaching of the fluorinated NO donor and its disulfide product after 9 day was only 0.6% (mol%) of the initial amount of NO donor loaded into the film. These new NO release PVDF-HFP films exhibit antimicrobial and anti-biofilm activities against both Gram positive S. aureus and Gram negative P. aeruginosa strains. The NO-releasing PVDF-HFP polymer can also be coated on Teflon tubing to release NO under physiological conditions for extended time periods. This NO-releasing PVDF-HFP copolymer with greatly reduced chemical leaching could help enhance the biocompatibility and antimicrobial activity of various biomedical devices. STATEMENT OF SIGNIFICANCE: Fluoropolymers have been widely used in creating various biomedical implants and devices. However, nitric oxide (NO) release fluoropolymers have not been well studied to date. Additionally, in the application of biomaterials doped with NO donors, a significant amount of NO donors and their byproducts almost always leach into aqueous environment. We now report an NO releasing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fluoropolymer by incorporating a new fluorinated S-nitrosothiol. The NO release can last for 16 days under physiological conditions. The total chemical leaching was determined to be only 0.6 mol% of the initial S-nitrosothiol loaded. As expected, significant antimicrobial/anti-biofilm activities of the NO release PVDF-HFP film were observed against Gram positive S. aureus and Gram negative P. aeruginosa bacterial strains.

Results of a near-peer musculoskeletal medicine curriculum for senior medical students interested in orthopedic surgery.

INTRODUCTION: It has been previously demonstrated that medical students do not achieve an adequate musculoskeletal knowledge base on graduation from American medical schools. Several curriculums have been developed to address this measured deficit. Students entering orthopedic surgery residencies have a better musculoskeletal knowledge foundation than their peers but still fail to achieve an acceptable level of proficiency on graduation from medical school. METHODS: Fourth-year medical students participating in senior elective rotations in orthopedic surgery over a 2-year period were given a series of lectures developed and presented by post graduate year 3 orthopedic surgery residents. Students completed a validated musculoskeletal competency examination and a survey following the conclusion of their experience, evaluating the effect of this curriculum. RESULTS: A total of 71 students over 2 years participated in the near-peer curriculum, with all students completing the validated test. The mean score for the students was 83.6%. Of the 71 students, 60 (84.5%) scored more than the previously published passing rate of 73.1%. There was no correlation identified with the mean test scores and the number of previous orthopedic surgery rotations. From the survey, 96% of the students rated the near-peer curriculum as appropriate for their level, whereas 75% noted that their own medical school's musculoskeletal curriculum was too advanced for their level of training. CONCLUSION: A series of lectures was developed by midlevel orthopedic residents for students interested in pursuing a career in orthopedic surgery. After participation in the curriculum, students scored 30-percentage points higher than a previously published test. This study demonstrates that a resident-initiated, near-peer curriculum increases the fundamental knowledge level of students entering orthopedic surgery. An added benefit appeared to be the skills obtained by the residents who created and delivered the lecture series.