In vitro neurotoxicity study with dorsal root ganglia for acrylamide and its derivatives

In Vitro Methods as a Tool in Neurotoxicity Studies

— There are several hundred industrial chemicals with neurotoxic potential. The neurotoxic risks of most of these chemicals are unknown. Additional methods are needed to assess the risks more effectively and to elucidate the mechanisms of neurotoxicity more accurately than is possible with the conventional methods.

This paper deals with general tasks concerning the use of in vitro models in the evaluation of neurotoxic risks. It is based on our previous studies with various in vitro models and on recent literature. The induction of glial fibrillary acidic protein in astrocyte cultures after treatment with known neurotoxicants (mercury compounds and aluminium) is discussed in more detail as an important response which can be detected in vitro.

When used appropriately with in vivo tests and with previous toxicological data, in vitro neurotoxicity testing considerably improves risk assessment. The incorporation of in vitro tests into the early stages of risk evaluation can reduce the number of animals used in routine toxicity testing, by identifying chemicals with high neurotoxic potential.

Microgels: From responsive polymer colloids to biomaterials

Microgels are network polymer colloid particles that can swell in a good solvent or as a result of electrostatic repulsion between charged groups produced by pH-triggered neutralisation. They have attracted considerable interest as both model colloids and for their potential applications. This discussion reviews the properties of microgel particles and the current understanding of their structure. The review concentrates on the period after an earlier microgel review by Saunders and Vincent [Adv. Coll. Interf. Sci., 1999, 80, 1]. A key challenge for microgel research has involved elucidation of the internal particle structure. Most microgels prepared by emulsion or precipitation polymerisation have a core-shell structure. The segment density is usually highest in the core. Here, we discuss relationships between microgel structure and dispersion stability. The reasons for the exceptional stability of microgel dispersions are considered. There are a number of favourable structural features that make microgels candidates for biomaterial applications and these are discussed. The main potential biomaterial applications that have been investigated for microgels to date are drug delivery and regenerative medicine. Poly(NIPAM) (N-isopropylacrylamide) microgels have been extensively studied in the context of drug delivery. Regenerative medicine research for microgels is an emerging area. Recent work involving the use of gelled microgel dispersions to support biomechanically meaningful loads is considered. We conclude with a discussion of promising directions for microgel research as biomaterials.

Poly(D,L-lactide-co-glycolide) dispersions containing pluronics: from particle preparation to temperature-triggered aggregation

In this work the preparation mechanism, properties and temperature-triggered aggregation of poly(D, L-lactide- co-glycolide) (PLGA) dispersions are investigated. The dispersions were prepared by interfacial deposition in aqueous solution containing Pluronic L62 (EO(6)PO(30)EO(6)) or F127NF (EO(101)PO(56)EO(101)), where EO and PO are ethylene oxide and propylene oxide, respectively. PLGA dispersions were also prepared in the absence of added Pluronic for comparison. The PLGA particles were characterized using SEM, photon correlation spectroscopy and electrophoretic mobility measurements. It was found that the hydrodynamic diameter (d) increased with PLGA concentration used in the organic solvent phase ( C PLGA(o) ). The value for d was proportional to C(PLGA)(o) (1/3). The value for d increased upon addition of 0.04 M NaNO(3) which demonstrated the importance of electrostatic interactions during particle formation. Electrophoretic mobility measurements were conducted as a function of pH and the data used to estimate the Pluronic layer thicknesses on the PLGA particles. The layer thickness was greatest for the PLGA particles prepared in the presence of Pluronic F127NF. PLGA dispersions containing Pluronic L62 exhibited temperature-triggered aggregation in the presence of 0.15 M NaNO(3). It was found that the critical temperature for dispersion aggregation (T(crit)) was comparable to the cloud point temperature ( T(cp)) for the parent Pluronic L62 solution. Conditions were established for achieving temperature-triggered aggregation at body temperature for PLGA particle/Pluronic L62 dispersions under physiological ionic strength and pH conditions. The PLGA/Pluronic L62 mixtures studied may have potential for use as injectable biodegradable implants for controlled release applications.