Grafting Of Functional Groups Research Articles

Selective Grafting of Primary Amines onto Carbon Nanotubes via Free-Radical Treatment in Microwave Plasma Post-Discharge

A novel strategy to graft functional groups at the surface of carbon nanotubes (CNTs) is discussed. Aiming at grafting nitrogen containing groups, and more specifically primary amine covalent functionalization, CNTs were exposed under atomic nitrogen flow arising from an Ar + N2 microwave plasma. The primary amine functions were identified and quantified through chemical derivatization with 4-(trifluoromethyl)benzaldehyde and characterized through X-ray photoelectron spectroscopy. The increase of the selectivity in the primary amines grafting onto CNTs, up to 66.7% for treatment of CNT powder, was performed via the reduction of post-treatment oxygen contamination and the addition of hydrogen in the experimental set-up, more particularly in the plasma post-discharge chamber. The analyses of nitrogenated and primary amine functions grafting on the CNT surface suggest that atomic nitrogen (N•) and reduced nitrogen species (NH• and NH2•) react preferentially with defect sites of CNTs and, then, only atomic nitrogen continues to react on the CNT surface, creating defects.

Photo-Initiated Lamination of Polyethylene (PE) and Poly(ethylene terephthalate) (PET)

Besides plasma-based processes, photo-initiated surface modifications have an interesting potential for adhesion promotion. This is of special interest with applications ranging from classical finishing to composites. Photo-chemical processes using continuous UV sources — monochromatic as well as broad band — are based on radical activation and ensuing reaction with the atmosphere. Achievable effects are addition of atoms — e.g., introduction of oxygen (photo-oxidation) resulting in increased surface energy — or grafting of functional groups. Both have certain potentials for adhesion promotion in a physico-chemical way. Based on the fundamental scheme of these processes — i.e., a photon-initiated radical reaction at the substrate-atmosphere interface — a direct 'inter-linking' of coating polymer and substrate is presented in this paper. The principal idea is to apply a thin layer of coating polymer on the substrate and irradiate this composite system at certain UV wavelengths. Given a low absorption of the radiation by the thin coating and — at the same time — a high absorption by the substrate, the radiation will penetrate the coating layer and generate radicals at the interface, which will induce cross-linking between the coating polymer and substrate. It is shown that for the example of laminates of polyethylene (PE) film on fabrics made of poly(ethylene terephthalate) (PET), extremely high adhesion strenghths are achieved without any use of additional adhesion promoters.

Synthesis of carbon nanotube–Poly aniline nano composite and evaluation of electrochemical properties

In this paper, carbon nanotube (CNT)- polyaniline (PANI) nanocomposites were developed from in situ polymerization of aniline. The CNT can be prepared by either acid treatment of CNTs suspension by grafting functional groups to CNTs surface. In this study, CNT and acid treatment CNT was used for preparation of nanocomposite. The PANI-CNT nanocomposite was characterized by FTIR, SEM. CNT can be prepared by either acid treatment of CNTs suspension to make them ionized or by grafting functional groups to CNTs surface. In addition, the electrochemical measurements such as cyclic voltametric (CV) curves showed that the conductivity of the obtained nanocomposite increased. Therefore, the supercapacitors behavior of polyaniline improves with adding CNT especially with acid treatment CNT.

Carbon Nanotube Nanoweb–Bioelectrode for Highly Selective Dopamine Sensing

A highly sensitive and selective dopamine sensor was fabricated with the unique 3D carbon nanotube nanoweb (CNT-N) electrode. The as-synthesised CNT-N was modified by oxygen plasma to graft functional groups in order to increase selective electroactive sites at the CNT sidewalls. This electrode was characterized physically and electrochemically using HRSEM, Raman, FT-IR, and cyclic voltammetry (CV). Our investigations indicated that the O(2)-plasma treated CNT-N electrode could serve as a highly sensitive biosensor for the selective sensing of dopamine (DA, 1 μM to 20 μM) in the presence of ascorbic acid (AA, 1000 μM).

Possible Two Different Mechanisms of Engraftment Failure in Cord Blood Transplantation: Graft Rejection and Poor Graft Function

Abstract 651 Backgrounds:Engraft failure remains a critical issue to be solved especially after cord blood transplantation (CBT). The factors such as limited doses of infused total nucleated (TNC) and CD34+ cells, HLA disparity, and anti-HLA antibodies are considered to induce engraftment failure. We studied the patterns and mechanisms of engraftment failure for patients who failed engraftment after CBT.Patients/methods: Medical charts on 429 transplant recipients of single unit CB with hematological diseases as the first allogeneic HSCT at Toranomon Hospital between January 2002 and May 2011 were retrospectively reviewed. Patients who did not meet the criteria of engraftment were subjected to the following analysis. Engraftment was defined when the neutrophil counts exceeded 0.5 × 109/L for 3 consecutive tests. Patients who died or had progressive disease before day 28 post-transplant were excluded. Result:Among 429 recipients, 67 were excluded due to early death before day 28 (n=52) and disease progression (n=15). In remaining 362 patients, 31 were diagnosed as engraftment failure. Median age was 62 years (range, 17–71). Underlying diseases were AML (n=16), ALL (n=5), MDS (n=2), NHL (n=6), and SAA (n=2). Twenty-three (74%) were in high risk disease status (MDS RAEB and beyond, or AL, NHL not in remission). Conditioning regimens mainly comprised of purine analogue-based reduced-toxicity regimens with fludarabine phosphate (125-180 mg/m2), melphalan (80-140 mg/m2) or busulfan (8-16 mg/kg) and 0–4 Gy of total body irradiation (TBI), and others. Graft-versus-host disease (GVHD) prophylaxis comprised of tacrolimus (TAC) (n=13) or cyclosporine alone (n=8), and TAC + mycophenolate mofetil (MMF) (n=10). Median number of total nucleated cells (TNC) and CD34+ cells were 2.45×106 /kg (range, 1.94 – 4.20), and 0.76×105 /kg (range, 0.21 – 1.35), respectively. Three had 1 antigen mismatch and 28 had 2 antigen mismatches in serological HLA typing, and 15 had allelic mismatches in more than 3 loci between host and graft. Twenty-two (71%) showed recipient-dominant chimerism (donor type <5%) at the diagnosis of engraftment failure, which were designated as graft rejection, and the other 9 (29%) showed donor-dominancy (donor type >90%), designated as poor graft function. Anti-HLA antibodies were present in 7 of the 13 patients tested (54%), including 2 (28%) who had a donor-specific antigen that targeted against UCB unit used. All these 7 patients who had anti-HLA antibody showed the graft rejection pattern. T-cell donor-recipient chimeric status was assessed in 14 patients. Nine who showed complete recipient dominant chimerism in T-cell fraction (donor type <5%) at early transplant phase (median day15, range, 8–17) developed graft rejection. In 9 patients who achieved complete donor chimerism, 4 complicated persistent infection (sepsis, invasive pulmonary aspergillosis), and the other 5 developed hemophagocytic syndrome (HPS). There were no statistically significant differences between graft rejection group versus poor graft function group in terms of TNC, CD34+ cell dose, HLA disparity, disease type (myeloid vs. lymphoid), disease status (standard vs. high), pretransplant conditioning (presence vs. absence of melphalan, or TBI), and GVHD prophylaxis (presence vs. absence of MMF) in this study. Discussion:These data demonstrated that the graft rejection pattern comprised 70% of engraftment failure. Presence of anti-HLA antibody showed close correlation with graft rejection, suggesting antigen-mediated graft rejection mechanism following CBT. Recipient dominant T-cell chimerism at early transplant phase (around day 15) strongly indicates impending graft rejection. All patients who showed poor graft function pattern accompanied by severe infection and/or HPS. This pattern is rarely seen in HSCT of other stem cell sources, suggesting unique characteristics of immune cells in CB graft as we reported. Disclosures:No relevant conflicts of interest to declare.

Computer aided detection of acute renal allograft dysfunction using dynamic contrast enhanced MRI

Aim of the workTo evaluate the feasibility of dynamic contrast enhanced (DCE) MR Renography (MRR) in evaluation of renal allograft dysfunction using the computer based technique for motion correction and creation of renographic curves. Materials and methodsBetween April 2007 and March 2008, 55 consecutive patients underwent kidney transplantation at our center from live related donors. There were 42 men and 13 women. The patients were divided into two main groups; first group (23 patients) included patients with stable graft function as indicated by normal serum creatinine (⩽1.3mg/dl). The second group (32 patients) included patients with acute kidney dysfunction as indicated by elevated serum creatinine. All were examined by DCE-MRI, ultrasound-guided needle biopsy was done for all the patients in the second group after MRI study. ResultsThere were 23 patients with normal graft function (group 1) and 32 patients with acute graft impairment (group 2); 24 with acute cellular rejection and eight with acute tubular necrosis (ATN). Morphological evaluation revealed preserved corticomedullary differentiation (CMD) in group 1 while in group 2 there were poor CMD in 16 cases and lost CMD in nine cases. Functional evaluation using the mean intensity of the medullary region, to create MR Renographic curves, was used with sensitivity, specificity and accuracy of 75%, 96% and 84%, respectively. ConclusionComputer aided analysis of renographic MR curves and the mean intensity of the medulla region have more important features than maximum intensity, it allows separation of normal kidney from impaired one but it cannot differentiate the underlying causes of the graft dysfunction.

Hydration status of patients with end-stage renal disease after kidney transplantation

This study was carried out to estimate the modification of hydration status within the first three months of renal transplantation. Fifty patients who underwent a first kidney allograft were prospectively followed for three months after renal transplantation to assess hydration status by bioimpedance spectroscopy. Two hours before the transplant procedure, 10/42 (23.8%) patients were overhydrated. Two days after surgery, 32/40 (80.0%) patients were overhydrated and at three months, 14/27 (51.9%) patients remained fluid-overloaded. Peritoneal dialysis (PD) patients had a lower hydration status (-0.60 L) than hemodialysis (HD) patients (0.70 L; p < 0.05) and better residual diuresis (41.7 vs. 8.3 mL/h for HD patients, p < 0.01). Compared with patients who had a delayed graft function (DGF) or a slow graft function (SGF), the immediate graft function (IGF) group had a better hydration status before transplantation (p = 0.031). At three months, 12/14 of the overhydrated patients had a creatinine clearance between 30 and 60 mL/min/1.73 m(2) . Patients receiving a first kidney transplant frequently have a hydration disorder. Transplantation is associated with increased hydration status, which seems to persist if DGF or SGF occurs.

Preparation of novel spherical PVA/ATP composites with macroreticular structure and their adsorption behavior for methylene blue and lead in aqueous solution

A novel spherical composite of polyvinyl alcohol (PVA) and attapulgite (ATP) with macroreticular structure, i.e. MR-PVA/ATP composites, was prepared as an adsorbent for some contaminations from aqueous environment, which would hold the advantages of PVA and ATP in the same time. The resulting adsorbents hold uniform and rich aperture with good mass transfer property, processing properties and stability. It has been proved with easy separation and excellent adsorption for methylene blue and lead in aqueous solution, and the adsorption rate will be accelerated when increasing porogen in its preparation. The adsorption process of methylene blue and lead on it includes both chemo-adsorption and physical adsorption. The adsorption process all fits the pseudo second order kinetics very well with rapid initial adsorption rate. The addition of attapulgite increased the adsorption capacity of lead ions significantly. By further graft functional groups on the ATP, it has potential to prepare various adsorbents to satisfy specific requirements. Such kind of adsorption material will perform a wide application prospect in the purification treatment for wastewater.

Urine neutrophil gelatinase-associated lipocalin is a marker of graft recovery after kidney transplantation

Delayed graft function (DGF), especially long-lasting DGF, complicates kidney transplant outcome. Neutrophil gelatinase-associated lipocalin (NGAL) is an acute kidney injury marker; therefore, we tested whether urine NGAL could predict DGF, prolonged DGF (lasting over 14 days), or the quality of kidney function in transplant recipients without DGF (non-DGF). We collected urine samples from 176 recipients transplanted with deceased donor kidneys before and various days after transplantation. A total of 70 transplantations had DGF, of which 26 were prolonged. Patients who developed DGF had a significantly slower decrease in urinary NGAL compared with those without DGF, such that day 1 NGAL predicted DGF (area under the curve (AUC) 0.75) and predicted DGF in 15 of 112 cases with day 1 urine output over 1 l (AUC 0.70) and in 19 of 86 cases with a day 1 decrease in creatinine over 50 μmol/l (AUC 0.74). The urinary NGAL level on day 1 predicted prolonged DGF (AUC 0.75), which had significantly worse 1-year graft survival (73%), compared with shorter DGF (100%). In non-DGF, high day 3 NGAL (greater than the mean) was associated with significantly worse kidney function at 3 weeks compared with low NGAL, but not at 3 months and 1 year. NGAL did not correlate with long-term function in DGF. Hence, day 1 urinary NGAL predicted DGF even when it was not clinically expected early on, and importantly, it predicted prolonged DGF that led to worse graft survival.

Functional defect-patching of a zeolite membrane for the dehydration of acetic acid by pervaporation

Pervaporation (PV) using zeolite membrane is one of the emerging technologies undergoing a rapid growth in recent years, regarded as an alternative method to distillation for its energy-efficient. However, grain boundary defects, especially for hydrophilic zeolite membranes, inevitably formed due to their polycrystalline structures and strong negative surface charges of Al-containing zeolites during hydrothermal synthesis, degrade their selectivity by providing nonselective transport pathway for permeating species. We show that functional defect-patching (FDP) can improve the PV performances of thin columnar membrane of a certain zeolite (mordenite) by eliminating grain boundary defects, by grafting functional polymer groups onto grain boundaries. This methodology enables the preparation of mordenite zeolite membrane (MZM) with high PV performances for the dehydration of acetic acid (AcOH) and holds promise for realizing high-throughput and scalable production of the membrane with improved energy efficiency. Furthermore, durable tests for acid stability showed that the FDP-treated membrane displayed a reasonably strong acid resistance. Finally, the products fabricated were characterized by a variety of techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), diffuse reflectance FT-IR spectroscopy (DRIFTS) and thermogravimetric analysis (TGA).

Influence of Early Graft Function After Renal Transplantation and Its Impact on Long-Term Graft and Patient Survival

Objective To determine whether early graft function after transplantation impacted graft and patient survivals. Materials and methods Between 1981 and 2008, we performed 1308 renal transplantations. Poor early graft function was defined as a Cockroft-Gault glomerular filtration rate < 60 mL/min or less at 1 and 3 months posttransplant. Patients who lost their kidney or died within the first 12 months after transplantation were excluded from the study. Multivariate statistical analysis used Cox proportional hazards models. Results Of the 1308 patients 994 (78.8%) displayed poor early graft function at 1 month after transplantation (glomerular filtration rate < 60 mL/min), while 268 (21.2%) showed normal function (glomerular filtration rate ≥ 60 mL/min). The 2- and 6-year graft survival rates among the poor early graft function group were 96.8% and 85.8%, respectively, while those among the control group were 97.0% and 88.3%, respectively. The 2- and 6-year patient survival rates in the poor early graft function were 98.5% and 89.8% versus 98.9% and 96.3% in the control group. Similar results were observed at 3 months posttransplant. Controlling for patient age, donor age, HLA-AB and -DR mismatches, cold ischemia time, acute rejection episodes, cyclosporine therapy, and waiting time for transplantation, we did not observe early graft function to be a risk factor for graft survival or patient survival. Glomerular filtration rate at 2, 5, and 6 years after kidney transplantation was significantly lower in the poor early graft function than in the control group. Conclusion This study suggested that the quality of early graft function had no significant effect on graft and patient survival rate, but did have a significant influence on long-term renal function.

Clinical Significance of Early-Onset Hyperuricemia in Renal Transplant Recipients

Background/Aims: It is undetermined whether the effect of uric acid (UA) on graft outcome is independent of graft dysfunction. This study was designed to explore whether early-onset hyperuricemia has clinical significance regardless of graft function. Methods: This study was conducted based on a retrospective chart review. We calculated time-averaged UA and estimated glomerular filtration rate from the values at 3, 6, and 9 months after transplantation. Cardiovascular complications during follow-up and long-term graft survival were assessed according to UA levels and graft function. Results: 351 patients were enrolled into this study. Hyperuricemia increased the risk of cardiovascular complications (HR = 2.8, 95% CI 1.1–7.1; p = 0.02), but reduced graft function did not. In the hyperuricemia group, 5- and 10-year graft survival was significantly lower than in the normouricemia group (89 and 81% vs. 96 and 92%, respectively; p = 0.02). In the reduced graft function group, these values were also lower than in the normal graft function group (89 and 81% vs. 96 and 93%, respectively; p = 0.02). In the multivariate analysis, both hyperuricemia and reduced graft function were independent risk factors for graft failure and the presence of both factors presented the highest risk. Conclusion: Early-onset hyperuricemia is a significant predictor of cardiovascular complications and graft survival independently of graft function.

Early Graft Function After Laparoscopically Procured Living Donor Kidney Transplantation

We determined predictors of poor early graft function after laparoscopic living donor kidney transplantation. We performed an institutional review board approved review of the living donor kidney transplantation database at our institution. Seven of the 510 transplants (1%) were excluded from study due to immediate graft nephrectomy for vascular complications. Of the remaining 503 transplants 48 (9.5%) and 18 (3.6%) had slow and delayed graft function, respectively. Recipient male gender (OR 2.03, 95% CI 1.05-3.91, p = 0.035), black ethnicity (OR 1.59, 95% CI 1.08-2.34, p = 0.020) and donor age (OR 1.03, 95% CI 1.00-1.05, p = 0.021) emerged as independent predictors of poor early graft function in multivariate logistic regression models. Poor early graft function strongly redisposed patients to acute rejection during year 1 (HR 3.43, 95% CI 2.04-5.77, p <0.0001) while grafts from genetically related donors conferred a protective effect (HR 0.40, 95% CI 0.24-0.66, p <0.0001). Three-year death censored allograft survival was lower in the delayed and slow graft function groups than in the immediate function group (89% and 87% vs 98%, p = 0.0068 and 0.0002, respectively). Overall 3-year patient survival was lower in the delayed than in the immediate function group (81% vs 94%, p <0.0001). Male black recipients of laparoscopically procured living donor kidney transplants from donors older than 50 years are at higher risk for poor early graft function, which in turn strongly predicts acute rejection during year 1. This is significant since excellent early graft function confers specific recipient and allograft survival advantages, and may assist physicians in better understanding the various recipient, donor and perioperative parameters that influence clinical outcomes.

Lipoxygenase-derived hydroxyeicosatetraenoic acids—novel perioperative markers of early post-transplant allograft function?

Active metabolites of arachidonic acid (AA), eicosanoids, strongly influence renal homeostasis. The aims of this study were to measure perioperative variations in lipoxygenase (LOX)-derived 5-, 12- and 15-hydroxyeicosatetraenoic (HETE) acids levels, and to examine whether (i) dynamics of these eicosanoid generation changes during the first 5 min of renal allograft reperfusion, (ii) examined HETE acids may influence perioperative 20-HETE generation, and (iii) LOX HETE may serve as perioperative markers of early post-transplant allograft function. Sixty-nine kidney recipients were divided into early, slow and delayed graft function (EGF, SGF and DGF, respectively) groups. Blood was taken directly before, and in the consecutive minutes of graft reperfusion. HETE concentrations were measured using liquid chromatography. Creatinine levels were measured during the perioperative period, as well as during follow-up visits (first post-transplant year). Our results demonstrated significant differences in the concentrations and dynamics of HETE changes between the examined groups. Moreover, observed changes in HETE concentrations were strongly associated with post-transplant graft function and perioperative 20-HETE synthesis. Application of cut-off limits for newly introduced markers, that is 71.72 ng/mL for 5-HETE(5), 12.3 ng/mL for 12-HETE△(5-0) and -6.1 ng/mL for 15-HETE△(5-0), resulted in 72.5-81.5% sensitivity and 50-54% specificity for SGF/DGF prediction. Moreover, mixed model analysis revealed that recipients classified according to results of 5-HETE(5) and 15-HETE△(5-0) significantly differ in 1-year post-transplant allograft function (P = 0.03 and P < 0.05, respectively), however, not in the frequency of acute rejections' episodes (P = 0.91 and P = 0.31, respectively). We hereby report that human kidney transplantations are accompanied by significant changes in LOX AA metabolism, which strongly influences and predicts early (1 year) post-transplant graft function.

M1023 Pre-Transplant Factors Influencing Indication for Simultaneous Liver-Kidney Transplantation

The hepatic peptide is a critical regulator of iron metabolism and inflammation. In this (first) study of post-operative hepcidin levels in patients undergoing liver transplantation we show that post-operative serum hepcidin levels identify patients with severe preservation/reperfusion injury and predict early graft dysfunction following liver transplantation. Methods: Serial serum hepcidin levels were measured daily by SELDI-TOFmass spectrometry (using stable isotope labelled hepcidin as internal standard) in 11 patients after liver transplantation. Liver biopsies (T0) were taken at the time of operation in 9/11 patients. Patient outcomes were correlated with clinicopathological results. Results: Five (5/11) patients had poor graft function after transplantation (graft cholestasis, elevated PT time and AST); these patients were more likely to have moderate/severe preservation injury on TO biopsy than patients with normal graft function and more likely to have received a liver from a nonheart beating than a heart-beating donor (3/5 vs 1/7). One patient with graft dysfunction was not biopsied. Whilst there was no difference in hepcidin values between the 2 groups at the time of transplantation (90 vs 76ng/ml p=0.68), the 5 patients with poor graft function had significantly higher hepcidin levels on the third day 3 post-transplantation compared to the 6 patients with mild preservation/reperfusion injury (Mean 135 (91-179) vs.39 (1761) ng/ml, p<0.01 ANOVA). Hepcidin rose by 39% between day 1 and 3 in the poor graft function group but fell by 49% in the group with normal function. Day 3 hepcidin rise anticipated graft cholestasis in those with severe preservation injury and did not correlate with AST or CRP. There was no difference in the two groups regarding age, cold ischaemic time, mean length of ITU stay or rate of septic complications. Conclusion: Serum hepcidin may be a better determinant of graft dysfunction post liver transplant than AST or CRP.

Modification of a Polyethersulfone Matrix by Grafting Functional Groups and the Research of Biomedical Performance

A new method for the functional modification of polyethersulfone (PES) is described in this paper in which PES was sulfonated by chlorosulfonic acid firstly and then chlorinated by phosphorus pentachloride. Thereby, chlorosulfonic groups (−SO2Cl) were introduced in PES successfully, and the degree of the chlorosulfonation was about 15%. Since the chlorosulfonic group is reactive enough towards the amino group (−NH2), the conformation of chlorosulfonic-based covalent bonding functional route could further extend the PES application area with versatile functionality. In this article, hydroxyl (−OH), carboxyl (−COOH), amino (−NH2) and methyl (−CH3) groups were grafted onto a PES matrix through the reaction of chlorosulfonic groups and the amino groups. The functional groups have effects on protein adsorption and cell behavior. The membrane modified with an amino group was in favor of cell adhesion and proliferation, and the membrane modified with hydroxyl and methyl did not so well as the membrane modified with an amino group, which will give guidance for biomaterial modification.

Dynamics of thromboxane level changes during early phase of allograft reperfusion

Thromboxane (Tx) is a metabolite of arachidonic acid, which exerts a significant influence on kidney homeostasis, and may be involved in the pathogenesis of allograft rejection. The aim of this study was to: examine the dynamics of TxB2 changes during early phase of kidney allograft reperfusion, and analyze whether the observed changes in the concentrations and direction of TxB2 changes, are associated with post-transplant graft function. Sixty-nine transplant recipients were divided into early, slow and delayed graft function group. Blood samples were collected directly before and during first the five minutes of allograft reperfusion. TxB2 concentrations were measured using ELISA. Creatinine and GFR levels were measured on the first, fifth, and 10th post-transplant day. The results demonstrated that during reperfusion significant differences in TxB2 concentrations occur in all groups. Moreover, significant differences in the concentrations, as well as in the dynamics of TxB2 changes between patients with immediate graft function, and individuals with allograft activation problems, were noticed. These differences were associated with post-transplant graft function. Human renal transplantations are accompanied by changes in TxB2 concentrations, and the dynamics of TxB2 changes is associated with early post-transplant graft function. Our results also highlight TxB2 as a potential pre-transplant marker of post-transplant allograft function.

No difference in clinical transplant outcomes for local and imported liver allografts

In the United States, liver allograft allocation is strictly regulated. Local centers have the first option to accept a donor liver; this is followed by regional allocation for those donor livers not used locally and then by national allocation for those donor livers not accepted regionally. This study reviews the outcomes of all liver allografts used over 6 years (2001-2007) and evaluates initial and long-term function stratified by the geographic source of the donor liver allograft. The records for 845 consecutive deceased donor liver transplants at a single center were reviewed. The geographic origin of the allograft was recorded along with donor and graft characteristics to determine the probable reason for graft refusal. Within our local organ procurement organization, there is 1 liver transplant center, and within the region, there are 8 active centers. Early graft failure included any graft loss within 7 days of transplant, and initial function was measured with liver enzymes 30 days post-transplant. Graft survival and patient survival were evaluated with Kaplan-Meier and Cox survival modeling. Median follow-up was 43 months. The geographic distribution of organs included local organs (562, 66%), regionally imported organs (126, 15%), and nationally imported organs (157, 19%). There were no differences between the 3 groups in initial graft function, intraoperative death, or early graft loss. Survival curves for the 3 study groups demonstrated no difference in survival up to 5 years post-transplant. In conclusion, liver allografts rejected for use by a large number of transplant centers can still be successfully used without early graft function or long-term survival being affected.

Hybrid nanocomposites for optical applications

Incorporating inorganic particles into conjugated polymer matrices is an area of current interest in the fields of optoelectronics and solar energy. The hybrid nanocomposites exhibit interesting physical properties thanks to good optical properties of polymers and to high carrier mobility of inorganic semiconductors. A judicious combination of organic/inorganic can therefore provide materials of low cost, ease processing, high stability, with specific electrical and optical properties. In the present study, we briefly review the composite materials that have been successfully utilized in the field of optoelectronics and photovoltaic conversion. We shall describe in particular a family of nanocomposites using polyhedral oligomeric silsesquioxanes (POSS) of general formula (RSiO 3/2) n where R is an organic group as a core. The composites are made by grafting functional polymer groups to the core, which allows the control of their optical properties. Such composites have high mechanical resistance and stability because of the special structure of the core. For illustration, we present a study of polyfluorene (PF)/POSS materials used as an active layer in organic light emitting diodes, with improved performance as compared to those using polymer only, and we discuss the role of the particles in the transport and emission processes in the devices studied.

Versatile One-Pot Synthesis of Supramolecular Plastics and Self-Healing Rubbers

We propose a strategy to obtain through a facile one-pot synthesis a large variety of supramolecular materials that can behave as differently as associating low-viscosity liquids, semicrystalline or amorphous thermoplastics, viscoelastic melts or rubbers. Such versatility is achieved thanks to simultaneous synthesis of branched backbones and grafting of associating units. This contrasts with usual synthetic pathways that rely on grafting functional groups on preprepared backbones. We use oligocondensation of fatty di- and triacids with diethylenetriamine and finely tune the molecular weight and degree of branching by end-capping some acid groups before condensation by reaction with aminoethylimidazolidone. Supramolecular assembly is formed thanks to complementary and self-complementary associations of amide, imidazolidone, and dialkylurea groups, and the stoichiometry directly controls the mesoscopic structure and properties.