Studies on the adsorption property and structure of polyamine-ended poly(ethylene glycol) derivatives on a gold surface by surface plasmon resonance and angle-resolved X-ray photoelectron spectroscopy.

The adsorption properties and structure of polyamine-ended poly(ethylene glycol) (PEG) derivatives on a flat gold surface were studied by means of surface plasmon resonance (SPR) and X-ray photoelectron spectroscopy (XPS) using PEG(5k)-block-poly[2-(N,N-dimethylamino)ethyl methacrylate](7.5k) [PEG-b-PAMA(5k/7.5k)] and pentaethylenhexamine-ended PEG(5k) [N6-PEG(5k)], which had 48 and 6 amino groups at the omega-end, respectively. The SPR analysis showed that the amount of PEG-b-PAMA(5k/7.5k) adsorbed onto the gold surface was not affected by the change in pH, and the desorption of this copolymer from the surface was not observed upon the addition of a solution at high salt concentration. The angle-resolved XPS (ARXPS) analysis revealed the structure of the PEG-b-PAMA polymer layer constructed on the gold surface: the PAMA segments were concentrated and located at the interface between the PEG layer and the gold surface. On the other hand, in the case of the PEG-graft-PAMA copolymer (PAMA-g-PEG)-modified gold surface, both the PAMA and the PEG segments homogeneously migrated to all regions of the constructed copolymer layer. The adsorbed amounts of N6-PEG(5k) under different pH conditions were constant and 2-3 times higher than those caused by the adsorption of single amino group-terminated PEG(5k) [PEG-NH(2)(5k)] and hydroxyl group-terminated PEG(5k) [PEG-OH(5k)]. The N6-PEG(5k)-modified gold surface showed a higher nonfouling property toward the adsorption of bovine serum albumin compared with the bare and the N6-modified gold surface. These results indicate that polyamine-ended PEGs were strongly immobilized onto the gold surface by polyamine anchors, even though electrostatic interaction between the polyamine and the gold substrate was not the dominant factor in this adsorption event. Furthermore, the formation of an almost complete phase-separated PEG/polyamine layer on the gold surface by polyamine-ended PEGs was strongly suggested.

Microbiological analysis and endoanal ultrasonography for diagnosis of anal fistula in acute anorectal sepsis.

BACKGROUND AND AIMS: Treatment of anorectal sepsis requires prompt surgical drainage, but it is important to identify any associated anal fistula for preventing recurrence. We evaluated whether microbiological analysis and/or endoanal ultrasonography could be used to predict anal fistula in patients with acute anorectal sepsis. METHODS: Five hundred fourteen consecutive patients with acute anorectal sepsis were studied. Clinical data, digital examination findings, endosonographic findings, and results of microbiological analysis were compared with definitive surgical findings of the presence or absence of anal fistula. RESULTS: Anorectal abscess with anal fistula was found in 418 patients, and anorectal abscess without anal fistula was found in 96 patients. Microbiological examination showed that Escherichia coli, Bacteroides, Bacillus, and Klebsiella species were significantly more prevalent in patients with fistula (P<0.01), and coagulase-negative Staphylococci and Peptostreptococcus species were significantly more prevalent in patients without fistula (P<0.01). Results of endoanal ultrasonography were concordant with the definitive surgical diagnosis in 421 (94%) of 448 patients studied. CONCLUSION: Acute anorectal sepsis due to colonization of "gut-derived" microorganisms rather than "skin-derived" organisms is more likely to be associated with anal fistula. When the microbiological analysis yields gut-derived bacteria, but no fistula has been found in the initial drainage operation, repeat examinations during a period of quiescence, including careful digital assessment and meticulous endosonography, are warranted to identify a potentially missed anal fistula.