Spectral and photophysical modifications of porphyrins attached to core-shell nanoparticles. Theory and experiment.

Plasmonic nanostructures, of which gold nanoparticles are the most elementary example, owe their unique properties to localized surface plasmons (LSP), the modes of free electron oscillation. LSP alter significantly electromagnetic field in the nanostructure neighborhood (i.e., near-field), which can modify the electric dipole transition rates in organic emitters. This study aims at investigating the influence of Au@SiO2core-shell nanoparticles on the photophysics of porphyrins covalently attached to the nanoparticles surface. Guided by theoretical predictions, three sets of gold nanoparticles of different sizes were coated with a silica layer of similar thickness. The outer silica surface was functionalized with either free-basemeso-tetraphenylporphyrin or its zinc complex. Absorption and emission bands of porphyrin overlap in energy with a gold nanoparticle LSP resonance that provides the field enhancement. Silica separates the emitters from the gold surface, while the gold core size tunes the energy of the LSP resonance. The signatures of weak-coupling regime have been observed. Apart from modified emission profiles and shortened S1lifetimes, Q band part intensity of the excitation spectra significantly increased with respect to the Soret band. The results were explained using classical transfer matrix simulations and electronic states kinetics, taking into account the photophysical properties of each chromophore. The calculations could reasonably well predict and explain the experimental outcomes. The discrepancies between the two were discussed.

Reduced loosening rate and loss of correction following posterior stabilization with or without PMMA augmentation of pedicle screws in vertebral fractures in the elderly.

BACKGROUND: Therapy of vertebral fractures in the elderly is a growing challenge for surgeons. Within the last two decades, the use of polymethylmethacrylate (PMMA) in the treatment of osteoporotic vertebral fractures has been widely established. Besides vertebroplasty and kyphoplasty, the augmentation of pedicle screws with PMMA found widespread use to strengthen the implant-bone interface. Several studies showed an enhanced pullout strength of augmented screws compared to standard pedicle screws in osteoporotic bone models. To validate the clinical relevance, we analyzed postoperative radiologic follow-up data in regard to secondary loss of correction and loosening of pedicle screws in elderly patients. MATERIALS AND METHODS: In this retrospective comparative study, 24 patients admitted to our level I trauma center were analyzed concerning screw loosening and secondary loss of correction following vertebral fracture and posterior instrumentation. Loss of correction was determined by the bisegmental Cobb angle and kyphosis angle of the fractured vertebra. Follow-up computed tomography (CT) scans were used to analyze the prevalence of clear zones around the pedicle screws as a sign of loosening. RESULTS: In 15 patients (mean age 76 ± 9.3 years) with 117 PMMA-augmented pedicle screws, 4.3 % of screws showed signs of loosening, whereas in nine patients (mean age 75 ± 8.2 years) with 86 uncemented screws, the loosening rate was 62.8 %. Thus, PMMA-augmented pedicle screws showed a significantly lower loosening rate compared to regular pedicle screws. Loss of correction was minimal, despite poor bone quality. There was significantly less loss of correction in patients with augmented pedicle screws (1.1° ± 0.8°) as compared to patients without augmentation (5° ± 3.8°). CONCLUSION: The reinforcement of pedicle screws using PMMA augmentation may be a viable option in the surgical treatment of spinal fractures in the elderly.

Intraoperative PEEP-ventilation during PMMA-injection for augmented pedicle screws: improvement of leakage rate in spinal surgery.

BACKGROUND: Within the last two decades the use of polymethylmethacrylate (PMMA) in the treatment of osteoporotic vertebral fractures has been established widely. Several techniques of cement application in spinal surgery have been described. Besides classical vertebroplasty, kyphoplasty and related techniques that reinforce stability of the fractured vertebral body itself, augmentation of pedicle screws became an issue in the past 10 years. Aim of this technique is strengthening of the implant-bone-interface and the prevention of loosening and failure of posterior instrumentation in limited bone quality due to osteoporosis. PMMA use in spinal surgery always bears the risk of cement leakage and cement embolism. There are only few publications dealing with cement leakage in pedicle screw augmentation. We examined our cohort concerning incidence and type of leakage in comparison to the literature. In particular, we evaluated a possible role of intrathoracic pressure during cementation procedure. PATIENTS AND METHODS: In this retrospective study 42 patients were included. Mean age was 74 (57-89) years. 311 fenestrated, augmented screws were analyzed postoperatively concerning leakage and subsequent pulmonary embolism of cement particles. Overall, there was a leakage rate of 38.3 %, and 28.6 % of patients showed pulmonary embolism of PMMA. During surgery, patients were in part ventilated with a positive end-expiratory pressure (PEEP) of 15 cmH2O during cement injection. These individuals showed significantly less leakage locally as well as less PMMA-emboli in the pulmonary circulation in contrast to patients ventilated without increased PEEP. CONCLUSION: PEEP elevation during administration of PMMA via fenestrated pedicle screws is reducing the leakage rate in spinal surgery. These beneficial effects warrant further evaluation in prospective studies.

[Pelvic injuries in childhood and adolescence: Retrospective analysis of 5-year data from a national trauma centre]. / Beckenverletzungen im Kindes- und Jugendalter: Eine retrospektive Analyse eines überregionalen Traumazentrums über 5 Jahre.

BACKGROUND: Pelvic fractures are uncommon injuries in paediatric trauma patients because of specific anatomical features. Due to the low incidence there is no standardized therapeutic algorithm. MATERIAL AND METHODS: This retrospective review evaluates paediatric pelvic fractures of a Level I Trauma Centre over 5 years. In addition, we compared the data with adult pelvic fractures and reviewed the literature. A total of 37 pelvic fractures (≤16 years) were documented, with an incidence of 9.9% in the child with multiple injuries. The most common injury mechanisms were traffic accidents, followed by falls from heights. RESULTS: Type A injuries occurred in 50% (type B: 16%, type C: 27%, acetabular injuries: 11%). Osteosynthesis was performed in nine cases. Therapeutic intervention was necessary in three cases of haemodynamically relevant bleeding; 97% of all children had associated injuries (mean ISS: 38). CONCLUSION: Our data showed some differences to the literature. Pelvic fractures are predictors for high injury severity. Despite similar fracture pattern, in contrast to adults most injuries could be treated non-operatively. In unstable or dislocated fractures open reduction and stabilization must be performed.

The biosynthesis of 8-O-methylated sialic acids in the starfish Asterias rubens--isolation and characterisation of S-adenosyl-L-methionine:sialate-8-O-methyltransferase.

The unusual, 8-O-methylated sialic acids have only been found in glycoconjugates of certain species of starfish. Using a detergent-solubilised extract of a particulate fraction from gonads of Asterias rubens, a specific methylation of endogenous and exogenous glycoconjugate-bound sialic acids was detected with [14C]-S-adenosyl-L-methionine ([14C]AdoMet) as the methyl donor. For this test, a filtration assay was developed using glutardialdehyde-fixed horse erythrocyte membranes as methyl acceptor. The enzyme catalysing this reaction, the sialate-8-O-methyltransferase, was purified 22000-fold in a yield of 13% by ion-exchange chromatography and two cycles of affinity chromatography on S-adenosyl-L-homocysteine-Sepharose. Upon SDS/PAGE under reducing conditions, the purified sialate-8-O-methyltransferase revealed two bands with apparent molecular masses of 58 kDa and 62 kDa. Since no evidence for the presence of subunits was found, the relationship between these two species is unknown. The enzyme was optimally active over a broad range of pH (7.4-8.3) and at 37 degrees C. After EDTA treatment, restoration of the activity depended, in contrast to most methyltransferases, on Mn2+ or Co2+, the latter to a lesser extent. Although both, free N-acetylneuraminic acid and N-glycoloylneuraminic acid were methylated, sialic acids alpha-glycosidically bound to a number of oligosaccharides and glycoproteins were better substrates. In the presence of 20 microM AdoMet, apparent Km values of 299 microM and 44 microM were found for N-acetylneuraminic acid and N-acetylneuraminyl alpha2,3-lactose, respectively. Using N-acetylneuraminyl alpha2,3-lactose as acceptor, an apparent Km of 7.1 microM was found for S-adenosyl-L-methionine. Therefore, the sialate-8-O-methyltransferase is the first enzyme known to modify both free and glycoconjugate-bound sialic acids.