Mechanical and drug delivery properties of a chitosan–tartaric acid hydrogel suitable for biomedical applications

The present investigation describes the synthesis and the characterization of a novel highly stable polysaccharidic hydrogel system, designed for modified drug delivery. Gels and films based on the biodegradable and biocompatible chitosan (CS) were prepared by a crosslinking reaction between the polysaccharide amino groups with tartaric acid, using the short‐range crosslinkers 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide (EDC) and N‐hydroxysuccinimide (NHS) as coupling agents. The aim of the study is to characterize the novel CS hydrogel by means of rheological and mechanical measurements; in vitro swelling, release, and degradation studies were also carried out. Obtained results show how the structure of the obtained networks can deeply affect dynamomechanical properties of the hydrogel as well as the delivery rate of loaded model drugs. The mechanical characterization of the hydrogel, in the form of films, indicates that the film elasticity increases as the water content in the hydrogel increases. Rheological studies evidenced that the different network structures can affect the elastic modulus of the system. Release studies of two model molecules, i.e., vitamin B12 and blue dextran, of different steric hindrance were carried out using both the bulk gel and the film. In vitro release of both drugs was evaluated in water and in Hepes to assess the suitability of this novel drug delivery system for pharmaceutical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cerebral autoregulation in patients with cirrhosis and ascites. A transcranial Doppler study

BACKGROUND/AIMS: Patients with cirrhosis and ascites usually show alterations of systemic hemodynamics and are thus prone to develop arterial hypotension, which might result in cerebral hypoperfusion if cerebral autoregulation is impaired. METHODS: We evaluated cerebral autoregulation in 15 patients with cirrhosis and ascites and 15 healthy subjects by monitoring mean blood flow velocity in the middle cerebral artery and arterial pressure during supine rest and passive tilting. RESULTS: Tilt provoked a drop of arterial pressure in both groups. Control subjects had a prompt recovery of mean flow velocity and a progressive recovery of arterial pressure, so that, after 120 s, both parameters had returned to baseline: at 20 s the recovery of flow velocity was faster (p<0.01) than that of blood pressure. By contrast, patients with cirrhosis had a delayed and incomplete recovery of both parameters (p<0.01 vs healthy subjects). In eight patients, the recovery of mean flow velocity paralleled that of arterial pressure, indicating an impaired cerebral autoregulation. These patients had a worse liver function, a higher cardiac index and lower peripheral resistance. CONCLUSIONS: Cerebral autoregulation is often impaired in patients with cirrhosis and ascites. These patients can develop cerebral hypoperfusion if arterial pressure falls abruptly.     

Preparation and characterization of a new gellan gum and sulphated hyaluronic acid hydrogel designed for epidural scar prevention

Postsurgical adhesions are a common problem in clinical practice, causing nerve compression, pain and discomfort. A new hydrogel based on gellan gum and sulphated hyaluronic acid was synthesized, with the aim to create an effective barrier for epidural scar formation. Physico-chemical properties of the gel were analyzed, and preliminary biocompatibility data (i.e. cytotoxicity) have been collected in view of its potential clinical use. The characterization of the new material demonstrated that the hydrogel, due to its high-viscosity, could effectively act as a barrier with a long in situ residence time. In addition, the hydrogel can be easily extruded from a syringe and its structure exhibits excellent stabilizing properties. Furthermore, biological assays showed that this gel is suitable for further preclinical development.