Poly(N-isopropylacrylamide) copolymer films as vehicles for the sustained delivery of proteins to vascular endothelial cells

The aim of this study was to establish the capacity of thermoresponsive poly(N-isopropylacrylamide) copolymer films to deliver bioactive concentrations of vascular endothelial growth factor (VEGF165) to human aortic endothelial cells (HAEC) over an extended time period. Films were prepared using a 50:50 (w/w) mixture of non-crosslinkable and crosslinkable copolymers of the following monomer compositions (w/w): 85:15, N-isopropylacrylamide (NiPAAm):N-tert-butylacrylamide (NtBAAm); and 85:13:2 NiPAAm:NtBAAm:acrylamidobenzophenone (ABzPh, crosslinking agent), respectively. After crosslinking by UV irradiation, the ability of films to incorporate a fluorescently labeled carrier protein (FITC-labeled BSA, 1 mg loaded per film), at 4 degrees C, was first established. Incorporation into the matrix was confirmed by the observation that increasing film thickness from 5 to 10 microm increased release from collapsed films at 37 degrees C (1.76 +/- 0.15 and 10.98 +/- 3.38 microg/mL, respectively, at 24 h postloading) and that this difference was maintained at 5 days postloading (1.81 +/- 0.25 and 13.8 +/- 2.3 microg/mL, respectively). Incorporation was also confirmed by visualization using confocal microscopy. When 10-microm films were loaded with a BSA solution (1 mg/mL) containing VEGF165 (3 microg/mL), sustained release of VEGF165 was observed (10.75 +/- 3.11 ng at 24 h; a total of 31.32 +/- 8.50 ng over 7 days). Furthermore, eluted VEGF165 increased HAEC proliferation by 18.2% over control. The absence of cytotoxic species in medium released from the copolymer films was confirmed by the lack of effect of medium (incubated with copolymer films for 3 days) on HAEC viability. In conclusion this study has shown that NiPAAm:NtBAAm copolymers can be loaded with a therapeutic protein and can deliver bioactive concentrations to human vascular endothelial cells over an extended time period.

Enhancement by haloperidol of the locomotor response induced by naloxone in morphine-treated guinea pigs

Guinea pigs given naloxone hydrochloride, 15 mg/kg subcutaneously (s.c.) 2 h after a single dose of morphine sulphate, 15 mg/kg s.c. exhibit a withdrawal response which is characterized by a marked increase in locomotor activity. In this study the effects of haloperidol on the morphine locomotor withdrawal response of guinea-pigs were investigated. Locomotor activity was measured in a cage fitted with a single infra-red photocell and detector. Haloperidol, at a dose of 1 mg/kg, s.c., given 0.5 h prior to administration of naloxone slightly enhanced the morphine locomotor withdrawal response, and at a dose of 10 mg/kg, markedly enhanced the response. Chronic pretreatment of guinea pigs with haloperidol, 1 mg/kg, daily for 21 days did not alter the locomotor withdrawal response. It remains to be established whether the enhancement by haloperidol of the opiate withdrawal response is a functional reflection of its interaction with dopamine, sigma or other receptors.

The infant walker. A previously unrecognized health hazard

The use of infant walkers within a large prepaid pediatric group practice was investigated. Of 195 patients (age range, 5 to 15 months) surveyed during a three-months) surveyed during a three-month period, 150 patients (77%) used infant walkers. Of those, 47 patients (31%) had suffered mishaps. These included closed head trauma, fractures, lacerations, tooth evulsion, and soft palate perforation. There is no proved benefit associated with the use of such walkers. The risk of injury associated with the use of infant walkers should be of concern for those physicians who care for preambulatory children.