Hydroxyl functionalized thermosensitive microgels with quadratic crosslinking density distribution.

N-isopropylacrylamide (NIPA) based uniform thermosensitive microgels were synthesized by dispersion polymerization by using relatively hydrophilic crosslinking agents with hydroxyl functionality. Glycerol dimethacrylate (GDMA), pentaerythritol triacrylate (PETA) and pentaerythritol propoxylate triacrylate (PEPTA) were used as crosslinking agents with different hydrophilicities. A protocol was first proposed to determine the crosslinking density distribution in the thermosensitive microgel particles by confocal laser scanning microscopy (CLSM). The microgels were fluorescently labeled by using hydroxyl group of the crosslinking agent. The CLSM observations performed with the microgels synthesized by three different crosslinking agents showed that the crosslinking density exhibited a quadratic decrease with the increasing radial distance in the spherical microgel particles. This structure led to the formation of more loose gel structure on the particle surface with respect to the center. Then the use of hydrophilic crosslinking agents in the dispersion polymerization of NIPA made possible the synthesis of thermosensitive microgels carrying long, flexible and chemically derivatizable (i.e., hydroxyl functionalized) fringes on the surface by a single-stage dispersion polymerization. The microgels with all crosslinking agents exhibited volume phase transition with the increasing temperature. The microgel obtained by the most hydrophilic crosslinking agent, GDMA exhibited higher hydrodynamic diameters in the fully swollen form at low temperatures than those obtained by PETA and PEPTA. Higher hydrodynamic size decrease from fully swollen form to the fully shrunken form was also observed with the same microgel.

Stimuli-responsive properties of conjugates of N-isopropylacrylamide-co-acrylic acid oligomers with alanine, glycine and serine mono-, di- and tri-peptides.

A random oligomer of N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc) with a AAc content of 3.1+/-0.19 mmol carboxylic acid groups per gram of the oligomer and with a number average molecular weight of 1400 was synthesised by a free radical polymerisation using AIBN in DMF. Then, mono-, di-, and tri-peptide conjugates of this oligomer were prepared by using carboxyl-ends-protected (with methyl ester hydrochloride) forms of alanine, glycine and serine, with a water-soluble carbodiimide. 95, 93, and 31% of the carboxylic acids were conjugated (loaded) at the first step (mono-peptides) with glycine, alanine and serine, respectively. At the second step, percentage of the conjugation of carboxylic acid groups with glycine, alanine and serine were between 99 and 80, 68 and 100, and 21 and 58%, respectively, while the third amino acids were attached to only 21-64% of the carboxylic acids available on the conjugate chains. A decrease was observed in the lower critical solution temperatures (LCSTs) of the amino acid conjugates at pH 4.0 compared with the unconjugated oligomer, which has LCST at 37.7 degrees C at the same pH. LCSTs of di- and tri-peptide conjugates at pH 4.0 were in the range of 38.4-43.3 degrees C, and 42.6-50.8 degrees C, respectively. At pH 7.4, LCSTs of the mono- and di-peptide conjugates were observed in the range of 41.6-43.9 degrees C, and 46.2-60.2 degrees C, respectively, while the co-oligomer at pH 7.4 did not show a LCST up to 60 degrees C. Tri-peptide conjugates did not display LCST at pH 7.4, except the one with glycine-alanine-serine sequence.

4-Methylcarbazole-3-carboxylic acid.

The title compound, C(14)H(11)NO(2), consists of a carbazole skeleton with carboxylic acid and methyl groups at positions 3 and 4, respectively. Molecules are linked about inversion centres by O-H.O hydrogen bonds [O.O 2.620 (3) A] to form centrosymmetric dimers.

Post-traumatic brain abscess: experience of 36 patients.

Thirty-six patients with post-traumatic brain abscess were managed over 18 years. They constituted 9.3% of all brain abscesses encountered during the same period. The head injury was associated with an external compound fracture in 20, internal compounding in three and was closed in 13 patients. The mean interval between the time of injury to presentation with an abscess was 113 days. This did not differ significantly in patients with closed and compound head injury, and amongst patients who had wound sepsis and with clean wounds after the injury. The occurrence of focal neurological deficit was more frequent in patients with a closed injury ( p < 0.05). Twenty patients underwent primary excision of the abscess with recurrence of the abscess in one patient. Of the 14 patients in whom the abscess was initially aspirated, eight patients required a subsequent excision. Excision was required in 18 patients (94.7%) with external compound injury, five (50%) of those with closed injury and in all patients with internally compound injuries. Two patients had 'coned' and died before they could be operated upon. The operative mortality in the absence of signs of herniation preoperatively was 12.5% in patients with compound injury and none among patients with closed head injury.