Aggregation of coronene: the effect of carboxyl and amine functional groups.

The aggregation of coronene is relevant to understand the formation of carbon nanomaterials, including graphene quantum dots (GQDs) that show exceptional photophysical properties. This article evaluates the influence of carboxyl and amine substituting groups on the aggregation of coronene by performing a global optimization study based on a new potential energy surface. The structures of clusters with substituted coronene are similar to those formed by un-substituted monomers, that is, stacked (non-stacked) motifs are favoured for small-size (large-size) clusters. Nonetheless, the presence of carboxyl and amine groups leads to an increase of the number of local minima of comparable energy. The clusters with substituted monomers have also shown to enhance the attractive component interaction, which can be attributed to weak induction and charge transfer effects and to stronger electrostatic contributions. Moreover, the calculated height of magic-number structures of the clusters in this work is compatible with the morphology of the GQDs reported in the literature.

Versatile Tetrablock Copolymer Scaffold for Hierarchical Colloidal Nanoparticle Assemblies: Synthesis, Characterization, and Molecular Dynamics Simulation.

A unique combination of molecular dynamics (MD) simulation and detailed size exclusion chromatography-multiangle light scattering (SEC-MALS) analysis is used to provide important a priori insights into the solution self-assembly of a well-defined and symmetric tetrablock copolymer with two acrylic acid (AA) outer blocks, two polystyrene (PS) inner blocks, and a trithiocarbonate (TTC) central group, prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. SEC-MALS experiments show that the copolymer forms aggregates in both tetrahydrofuran and N,N-dimethylformamide (DMF), even in the presence of different salts, but not in 1,4-dioxane (dioxane). Combined with MD simulations, these results indicate that the AA units are the main cause of aggregation through intermolecular hydrogen bonding, with additional stabilization by the central TTC. The block copolymer chains self-assemble in dioxane by adding cadmium acetate, originating flowerlike inverse micelles with a cadmium acrylate core and the TTC groups in the outer surface of the PS corona. The micelles were used as nanoreactors in the templated synthesis of a single cadmium selenide (CdSe) quantum dot (QD) in the core of each micelle, whereas the shell TTC groups can be converted into thiol functions for further use of these units in hierarchical nanostructures. Only in dioxane where simulations and SEC-MALS suggest an absence of copolymer aggregates prior to cadmium acetate addition do well-dispersed and highly luminescent CdSe QDs form by templated synthesis. These results provide valuable insights into the self-assembly of RAFT copolymers in different solvent systems as it relates to the preparation of emissive QDs with polymer-spaced thiol functionality for binding to gold nanostructures.

Synthesis of water-soluble gold clusters in nanosomes displaying robust photoluminescence with very large Stokes shift.

This paper reports a novel procedure using nanosomes, made of bola-hydroxyl and mercapto-palmitic acids, for the production of gold clusters with robust luminescent emissions and very large Stokes shifts. It shows that these results cannot be explained by the currently accepted mechanism based on ligand-to-metal charge transfer absorptions involving electron-rich ligands attached to the cluster core. Exhaustive characterization of the cluster samples using Mass Spectrometry, HR-TEM/STEM, XPS, EXAFS, and steady-state and time-resolved luminescence allows to deduce that a mixture of two cluster sizes, having non-closed shell electronic configurations, are firstly generated inside the nanosome compartments due to the difference in bonding strength of the two types of terminal groups in the fatty acids. This initial bimodal cluster size distribution slowly evolves into very stable, closed-shell Au cluster complexes (Au6-Au16 and Au5-Au14) responsible for the observed luminescent properties. The very small (≈1.2 nm) synthesized cluster complexes are water soluble and suitable to be used for the conjugation of biomolecules (through the terminal COO(-) groups) making these systems very attractive as biomarkers and offering, at the same time, a novel general strategy of fabricating stable atom-level quantum dots with large Stokes shifts of great importance in many sensor applications.

Effect of ischemic preconditioning and postconditioning on liver regeneration in prepubertal rats.

BACKGROUND: Liver regeneration has great importance for transplantation, especially in children; however, it has not been studied sufficiently in development animals. Ischemia-reperfusion injury is a problem, and strategies such as ischemic preconditioning and postconditioning are not well defined regarding regeneration. OBJECTIVE: This study sought to evaluate liver regeneration with modulation by ischemic preconditioning and postconditioning in prepubertal rats subjected to total ischemia and reperfusion. METHODS: Thirty-five 5-week-old female Wistar rats were divided into groups of 7 animals each: control group (SHAM), 70% hepatectomy (HEP), total ischemia 30 minutes before hepatectomy (IR), ischemic preconditioning 10/10 minutes before ischemia (PRE), and two 30/30-second ischemic postconditioning cycles after ischemia and hepatectomy (POS). All animals were subjected to 24-hour reperfusion. Aspartate aminotransferase and alanine aminotransferase activity were measured to evaluate liver damage, and histological analysis, proliferating cell nuclear antigen (PCNA) and regenerated mass liver were used to evaluate liver regeneration. Statistical analyses were performed using ANOVA and Kruskal-Wallis test. RESULTS: Alanine aminotransferase and aspartate aminotransferase levels were significantly lower in conditioned groups than in the IR group. Regarding mitotic index, IR > control group and HEP (P < .05), PRE and POS were not significantly different from IR, and POS > HEP (P < .05). PCNA analysis showed that IR > HEP (P < .01), PRE < IR (P < .01), and no significant differences were observed between POS and IR groups. No significant differences in regenerated mass liver were observed between conditioned groups and HEP. CONCLUSIONS: Ischemic postconditioning prevented ischemic injury, promoted greater liver regeneration, and should be further investigated as an alternative better than ischemic preconditioning.

Polymer-coated nanoparticles by adsorption of hydrophobically modified poly(N,N-dimethylacrylamide).

We prepared a reactive random copolymer of N-acryloxysuccinimide and N,N-dimethylacrylamide (DMA) by reversible addition-fragmentation chain transfer polymerization, with Mn ≈ 50k and 23 mol % reactive NAS groups. This copolymer was subsequently modified with hydrophobic (dodecyl) and fluorescent (pyrene, PY; phenanthrene, PHE; or anthracene, AN) side groups, to obtain fluorescent amphiphilic polymers with the same backbone and different substituents. These polymers were adsorbed onto model (ca. 130 nm diameter) poly(butyl methacrylate) nanoparticles, and the size and structure of the adsorbed layer were evaluated using a combination of fluorescence techniques and light scattering. The total diameter increases very fast with polymer concentration up to ca. 140 nm, and then more slowly to 154 nm, stabilizing at this value which corresponds to a polymer shell thickness of ca. 12 nm. In order to evaluate the distribution of hydrophobic groups on the adsorbed polymer layer, we used Förster resonance energy transfer between PHE- and AN-labeled poly(DMA) chains. The obtained concentration profile of the adsorbed polymer corresponds to a coated particle radius which is only slightly smaller than the hydrodynamic radius measured in the same conditions, indicating that the dyes are not located at the particle interface but mostly distributed across the adsorbed layer. Finally, we observed that hydrophobically modified PHE-labeled poly(DMA) chains adsorbed to the nanoparticles were very efficiently displaced by identical hydrophobically modified chains with five times their molecular weight (Mn ≈ 250k) but labeled with PY.

Impact of model for end-stage liver disease score on long-term survival following liver transplantation for hepatocellular carcinoma.

BACKGROUND AND AIMS: Survival rates after orthotopic liver transplantation (OLT) for hepatocellular carcinoma (HCC) have significantly increased after Milan criteria and Model for End-Stage Liver Disease (MELD) score implementation. However, few studies have reported this survival in countries with organ donor shortages over a period of 10 years and long waiting lists. METHODS: This retrospective analysis of clinical data from 93 consecutive HCC patients who underwent OLT from June 2001 to September 2011 excluded 22 who underwent living donor liver transplantation (LDLT). Seventy-one deceased donor liver transplantations (DDLT) were evaluated before and after the MELD era. Kaplan-Meier analysis was used to plot survival rates. The follow-up was 2 months to 10 years. RESULTS: The overall survival and recurrence rates at 10 years were 67% and 12.2%, respectively. After MELD, patient survival at 5 years decreased from 70% to 64% and the recurrence rate decreased from 15.3% to 12.5%. The most frequent recurrence sites were lung and liver. CONCLUSION: In our center MELD score implementation had a small impact on long-term survival post OLT for HCC.

The influence of nanoparticle architecture on latex film formation and healing properties.

We present a study of chain interdiffusion in films formed by specially architectured PBMA nanoparticles by Förster Resonance Energy Transfer -FRET. Polymer nanoparticles contained linear chains with narrower molecular weight distributions than other previous reports, allowing a more detailed study. Apparent fractions of mixing and diffusion coefficients, determined from the quantum efficiency of energy transfer, were used to characterize the interdiffusion mechanism in the different films. The resistance of the films to dissolution by a good solvent was finally correlated with the interdiffusion results, in order to get information about film healing. We concluded that whenever interdiffusion occurs between nanoparticles containing linear chains and fully cross-linked nanoparticles, healing becomes more effective in spite of showing slower interdiffusion. We also observed that particles with longer chains are more effective for film healing. Finally, we concluded that interdiffusion occurs both ways across interfaces in blends formed by particles swollen with linear chains of different molecular weights.

Tuberculosis in liver transplant recipients: prophylaxis in an endemic area.

BACKGROUND: Tuberculosis (TB) has a high prevalence in Brazil. The scenario of liver transplantation (LT) creates challenges: atypical presentation, treatment hepatotoxicity, and increased mortality. The majority of TB cases after transplantation represent reactivation of latent infections; therefore, prophylaxis (PX) plays a major role. The aim of this study was to evaluate the benefits of PX after LT based on a pretransplantation tuberculin test (TT) in an endemic area. METHODS: Retrospective analysis of medical data from 376 adult cirrhotic patients undergoing OLT from 2001 to 2009. RESULTS: Among 191 selected patients, 137 (71%) showed a pretransplant TT including 41 (30%) with a TT ≥5 mm. The 17 (40%) of these patients who were prescribed PX did not experience TB. Prophylaxis was discontinued in 5 patients (20%) owing to suspicion of hepatotoxicity (medium serum alanine transaminase 175 U/L). In the group without PX, we diagnosed 1 case of pulmonary TB. The overall prevalence of anergic patients in the cirrhotic phase was 65% and prevalence of TB 1%. CONCLUSIONS: The prevalence of TB was similar to that reported in the literature, but positivity to TT was higher (34% vs 25%), possibly because of the endemicity of the area. There was a lower prevalence of extrapulmonary disease and no mortality. No patient undergoing PX with isoniazid, although incomplete due to suspicion of hepatotoxicity displayed TB. One patient without PX was affected by TB. The drug was effective but not always safe.

Vascular complications after living donor liver transplantation: a Brazilian, single-center experience.

BACKGROUND: In living donor liver transplantation (LDLT), vascular complications are more frequently seen than in deceased donor transplantation. Early arterial, portal vein, or hepatic vein thromboses are complications that can lead to graft loss and patient death. The aim of this study was to assess the incidence, treatment, and outcome of vascular complications after LDLT in a single Brazilian center. METHODS: Between December 2001 and December 2010, we performed 130 LDLT. Sixty-four recipients were children (27 weighing <10 kg). RESULTS: Nine recipients had vascular complications. Hepatic artery thrombosis (HAT) occurred in 4 (3.1%), portal vein thrombosis (PVT) in 3 (2.3%), and hepatic vein thrombosis (HVT) and hepatic arterial stenosis (HAS) in 1 (0.8%) patient each. Complications were identified by Doppler and confirmed by angiography or angiotomography. Patients with HAT were listed for retransplantation. One died before retransplant. Two children were submitted to retransplantation; one is still alive, with neurologic sequelae. One adult with HAT was retransplanted with a deceased donor graft and is doing well 58 months after surgery. Two patients with PVT died as a consequence of graft malfunction. In the other case, portal vein arterialization was performed, but patient died 11 months posttransplant. HVT was detected after cardiac reanimation and was treated with an endovascular stent. This patient died 3 months after LDLT. HAS was diagnosed after liver abscess development and was successfully treated by endovascular angioplasty. No recurrence was observed after 22 months. Follow-up ranged from 9 to 117 months. CONCLUSION: Pediatric patients are more prone to develop vascular complications after LDLT. Long-term survival was statistically lower for recipients with vascular complications (33.3% vs 77.7%; P = .008).

Surgical complications in 100 donor hepatectomies for living donor liver transplantation in a single Brazilian center.

The rising demand for liver transplantation has continued to outspace the availability of deceased donor organs, leading to the need for other treatment options including living donor liver transplantation (LDLT). A precise evaluation of surgical complications is the most important issue in this setting. There are controversies about donor morbidity with reports ranging from 13%-75%. The aim of this study was to retrospectively analyze 100 LDLTs performed in a single Brazilian center from December 2002 to August 2008, stratifying the complications according to Clavien's scoring system. None of the donors experienced life-threatening complications or died. The majority of donors (n = 74) did not suffer any complication. Twenty-eight complications were observed in 26 patients. Fifty-seven hepatectomies were performed for adult and 43 for pediatric transplantations. According to the Brisbane classifications, we performed 49 right and 2 left hepatectomies as well as 49 left lateral segmentectomies. According to Clavien, the complications were as follows: grade I (n = 11; 39.2%); grade II (n = 8; 28.5%); and grade III (n = 9; 32.3%). No patient presented with grade IV or V. The most common problem a biliary tract injury, similar to other series. In this Brazilian series, hepatectomy for LDLT was a safe procedure with low morbidity, regardless of the type of liver resection. This practice will probably continue to grow to alleviate the pressure of growing waiting lists.

Evaluation of living donor liver transplantation: causes for exclusion.

The decision to perform organ donation surgery involves a series of risks for the live donor including death. The aim of this study was to evaluate exclusion criteria for living donor liver transplantation, as well as to identify the rate of exclusion in each of the 3 process phases according to the Live Donor Evaluation Protocol for adult and child recipients. From December 2001 to December 2007, we evaluated 223 donors among whom 142 were excluded in various phases. The data were statistically evaluated. Among the 142 excluded donors, 113 (79.6%) had an adult recipient. The elimination rates for adult recipients were as follows: 68 cases in phase I, 41 cases in phase II, and 4 cases in phase III. Concerning child recipients, 29 (20.4%) donors were excluded: 17 in phase I, and 12 in phase II. Concerning adult recipients, sons and daughters were the largest part of the excluded donors, with withdrawal as the principal reason for exclusion followed by recipient death. Regarding child recipients the parents represented the largest number of excluded donors due to withdrawal followed by abnormal blood test results. Thus, 36.5% of potential donors were effective donors.

Ectopic placement of Sengstaken-Blakemore device to correct outflow obstruction in liver transplantation: case reports.

Liver transplantation is a complex procedure that has become the treatment for some end-stage liver diseases. Some technical features are important for the success of the transplantation, including the patency of the vascular anastomoses. In cadaveric whole organ liver transplantation, a large right subphrenic space may contribute to a twist of the inferior vena cava, leading to outflow obstruction, simulating an acute Budd-Chiari syndrome. Some devices can be used to correct this drainage problem. Herein, we have described 2 cases in which the Sengstaken-Blakemore balloon was safely used, in an ectopic position, to fix drainage complications in whole liver orthotopic transplantation.

Cellulitis and nodular skin lesions due to Fusarium spp in liver transplant: case report.

Fusariosis is one of the emerging invasive fungal infections over the last decade. However, its recent rise has been in its ability to produce disseminated infection in severely immunosuppressed patients with neutropenia. In solid organ transplantation, fusariosis remains an uncommon picture mainly with nodules, subcutaneous abscesses, ulcers, or necrotic skin lesions resembling erthyma gangrenosum. Herein, we have reported a case of cellulitis, subcutaneous nodules, and abscesses due to Fusarium spp in a liver transplantation patient who was successfully treated with polyenes and surgical resection.

Evaluation of the pulse pressure variation index as a predictor of fluid responsiveness during orthotopic liver transplantation.

BACKGROUND: The pulse pressure variation (PPV) index has been shown to be a reliable predictor of fluid responsiveness (FR) in a variety of clinical settings. However, it has not been formally evaluated in the setting of orthotopic liver transplantation (OLT). METHODS: Fifteen (n=15) patients undergoing OLT were enrolled in this study. All patients were monitored with a modified pulmonary artery catheter which measured the cardiac output on a semi-continuous basis. A fluid challenge (FC) with 350 ml of colloid was attempted during the following stages of surgery: hepatectomy (TH), anhepatic phase (TA), early post-reperfusion [(TE)--during the first 30 min], late post-reperfusion [(TL)--after hepatic artery anastomosis], and at the beginning of abdominal closure (TC). PPV and stroke volume index (SVI) were recorded at baseline and 5 min after the FC. Each individual FC which raised the SVI more than 10% from baseline was classified as responsive (R); otherwise, it was considered non-responsive (NR). RESULTS: Forty-one FCs were performed, with 14 (34%) classified as responsive and 27 (66%) as non-responsive. The baseline PPV did not differ significantly between the R and NR groups, showing considerable overlap of its values throughout the procedure [R vs NR; TH: 20% (inter-quartile range 7-32) vs 7% (5-14); TA: 10% (7-14) vs 19% (12-21), and TE+TL: 7% (5-11) vs 9% (7-16)]. CONCLUSIONS: Under the conditions of this study, the PPV index was not shown to be a reliable predictor of FR during OLT. Further studies are warranted to elucidate the role of this and other dynamic indexes in this specific setting.

Living donor liver transplantation for acute liver failure: a single center experience.

OBJECTIVE: Orthotopic liver transplantation (OLT) is the principal therapy for acute liver failure (ALF). The mortality on the waiting list for deceased donor liver transplantation (DDLT) is high, principally in countries where donation rates are low. Living donor liver transplantation (LDLT) seems an option for the treatment of ALF, although some ethical issues need to be considered. Herein we have evaluated LDLT results among patients with ALF and discussed the ethical aspects of procedures performed in emergency situations. PATIENTS AND METHODS: From March 2002 to October 2008, we performed 301 liver transplantations, including 103 from living donors. ALF was responsible for 10.6% of all transplantations; LDLT was only considered for pediatric recipients among whom 7 children displayed ALF. RESULTS: One patient died on postoperative day 33 due to hepatic artery thrombosis. One patient died at 2 months after transplantation due to biliary sepsis, resulting in an overall survival rate of 71%. The average time for donor discharge was 5 days. No mortality or major complications were observed. CONCLUSIONS: The survival of children with ALF undergoing LDLT was comparable to published data. Furthermore, despite the fact that the available time to prepare the donors was limited, no serious complications were observed in the postoperative period. Thus, using living donors for children with ALF is an effective, safe alternative that can be extremely useful in countries with low donation rates.

Evaluation of the right ventricular ejection fraction during orthotopic liver transplantation under propofol anaesthesia.

BACKGROUND: The right ventricular ejection fraction pulmonary artery catheter (RVEF-PAC) has been widely used to monitor the right ventricular (RV) function during orthotopic liver transplantation (OLT). However, the evaluation of the RVEF during this procedure during propofol anaesthesia has not been described. METHODS: Twenty consecutive patients undergoing OLT without veno-venous bypass were studied. Anaesthesia was maintained with propofol, remifentanil and atracurium infusions. All patients were monitored with a modified pulmonary artery catheter (RVEF-PAC), which continuously measures the RVEF. Haemodynamic data were recorded at: baseline (TB), anhepatic stage (TA), and 1, 5, 10, and 30 min post-reperfusion of the graft. RESULTS: The baseline RVEF was decreased [40% (sd 6)] and remained so throughout the OLT. A biphasic pattern was revealed, with the RVEF reaching its lowest values during TA [34% (7)] and gradually returning toward baseline at T30 [39% (8)]. Clinical significant RV dysfunction did not occur. CONCLUSIONS: Although the baseline RVEF was decreased, it showed only minor alterations throughout the procedure, suggesting that the RV function is not significantly compromised during OLT under propofol anaesthesia.

Biochemical and structural characterisation of cutinase mutants in the presence of the anionic surfactant AOT.

The reactivity, stability and unfolding of wild-type (WT) Fusarium solani pisi cutinase and L153Q, S54D and T179C variants were studied in the absence and presence of the dioctyl sulfosuccinate sodium salt (AOT) surfactant. In the absence of surfactant the S54D variant catalytic activity is similar to that of the WT cutinase, whereas L153Q and T179C variants show a lower activity. AOT addition induces an activity reduction for WT cutinase and its variants, although for low AOT concentrations a small increase of activity was observed for S54D and T179C. The enzyme deactivation in the presence of 0.5 mM AOT is relatively slow for the S54D and T179C variants when compared to wild-type cutinase and L153Q variant. These results were correlated with secondary and tertiary structure changes assessed by the CD spectrum and fluorescence of the single tryptophan and the six tyrosine residues. The WT cutinase and S54D variant have similar secondary and tertiary structures that differ from those of T179C and L153Q variants. L153Q, S54D and T179C mutations prevent the formation of hydrophobic crevices responsible for the unfolding by anionic surfactants, with the consequent decrease of the AOT-cutinase interactions.

Liver transplantation for acute liver failure: trying to define when transplantation is futile.

BACKGROUND: Recently, the model of end-stage liver disease (MELD) index has been used to select patients with acute liver failure (ALF) or transplantation. By the time the indication for orthotopic liver transplantation (OLT) is defined, the patient's clinical status may worsen. OBJECTIVE: In this study, MELD was used to define patients beyond OLT. METHODS: Among adult patients ALF was responsible for 17 OLT. Their medical records were reviewed to calculate the MELD score just before the OLT. MELD of the deceased patients after OLT (group 1, n=8), was compared with the MELD score of living recipients (group 2, n=9). Creatinine level, need for dialysis, use of vasoactive amines, and mechanical ventilation before OLT were also analyzed in these groups. A significant difference was defined when P<.05. RESULTS: The mean MELD score+/-SD was 51.86+/-12.3 for group 1, and 38.47+/-7.1 for group 2 (P=.02). There was no difference between the creatinine values for patients in the 2 groups (P=.20). Also, the use of vasoactive amines or the need of dialysis before OLT were not different (P=.12 and P=.25, respectively). Group 1 was more frequently under mechanical ventilation, and showed a 4.29 relative risk for death after OLT. CONCLUSION: MELD score could be useful to define the prognosis of OLT among patients with ALF.

Interfacial behavior of poly(isoprene-b-methyl methacrylate) diblock copolymers and their blends with polystyrene at the air-water interface.

The interfacial behavior of poly(isoprene-b-methyl methacrylate) diblock copolymers (PI-b-PMMA), with similar PMMA blocks but differing in the percentage of PI segments, SP19 (5% PI) and SP38 (52% PI), was studied at the air-water interface. The surface pressure-area (pi-A) isotherms, compression-expansion cycles, and relaxation curves were compared with those of the PMMA homopolymer. The short hydrophobic PI block of SP19 does not contribute to the mean molecular area at low surface pressures and yet has a negative contribution (condensing effect) when the surface pressure increases. On the contrary, the long PI block of SP38 contributes considerably to the surface area from low to high surface pressures. The A-t relaxation curves compare well with those of PMMA at low surface pressures (pi = 2 mN.m-1), but not at intermediate and high pressures (pi = 10, 30 mN.m-1), where a clear dependence on the length of the PI block was observed. The quantitative analysis of the relaxation curves at high pressures shows both a fast and slow component, attributed mostly to the local and middle-to-long-range reorganization of PMMA chains, respectively. PI-b-PMMA diblocks and PMMA were further blended with PS. The PS and PMMA are immiscible at the air-water interface. The addition of PS does not change the pi-A isotherm of PMMA, but the copolymers blended with PS form films that are more condensed at low pressures. The Langmuir-Blodgett (LB) films transferred onto mica substrates were analyzed by atomic force microscopy (AFM). The LB films of single diblocks are uniform, while those of PI-b-PMMA and PMMA blended with PS show aggregates with variable patterns.

Preparation and surface characterization of polymer nanoparticles designed for incorporation into hybrid materials.

We prepared water dispersions of poly(n-butyl methacrylate-st-butyl acrylate) crosslinked core-shell nanoparticles functionalized with different amounts of trimethoxisilane (TMS) groups in the outer shell. The purpose of the TMS groups is to chemically bind the rubbery particles to a nanostructured silica network, using sol-gel copolymerization. Here, we present nanoparticles containing 13 mol % and 30 mol % of TMS groups in the outer shell and compare their surface morphology with particles that do not contain TMS. The particles are prepared by a two-step seeded emulsion polymerization technique at neutral pH. In the first step, we obtained crosslinked seed particles (44 nm in diameter) by a batch process. In the second step, we used a semi-continuous emulsion polymerization technique under starved feed conditions to obtain monodispersed particles of controlled composition and size (ca. 100 nm in diameter). Fluorescence decay measurements were performed in situ on the dispersions, using a pair of cationic dyes adsorbed onto the surface of the nanoparticles: rhodamine 6G as the energy transfer donor and malachite green carbinol hydrochloride as the acceptor. The kinetics of Förster resonance energy transfer (FRET) between the dyes is sensitive to the donor-acceptor distance, allowing us to obtain the binding distribution of the dyes at the nanoparticle surface. For the unmodified nanoparticles, we found a dye distribution that corresponds to an average interface thickness of delta = (5.2 +/- 0.2) nm. For the samples containing 13 mol % and 30 mol % of TMS groups in the outer shell we obtained broader interfaces, with widths of delta = (6.2 +/- 0.2) nm and delta = (6.5 +/- 0.1) nm respectively. This broadening of the distribution with the surface modification is interpreted in terms of the increase in free volume of the shell caused by the TMS groups. Finally, we studied the effect of temperature on the water-polymer interface fuzziness, in order to evaluate the accessibility of the TMS groups during the sol-gel synthesis of nanostructured hybrid materials.