BegbrokeNano Instruments: TEM

TEM, Transmission Electron Microscopy JEOL 2010


- LaB6 electron gun and can be operated between 80 and 200kV
- Resolutions of 0.19nm, an electron probe size down to 0.5nm and a maximum specimen tilt of ±10 degrees along both axes. (Update, the ARP was fitted in 2002 so the tilt range is much improved, with a small loss of resolution and probe performance)
- Specimen holders:
- Single tilt (±10 degrees)
- Double tilt (±10 degrees)
- Low temperature double tilt (±10 degrees) liquid helium to below 10K.
- Oxford Instruments LZ5 windowless energy dispersive X-ray spectrometer (EDS) controlled by INCA. It has facilities for point analysis as well as mapping and line scanning through the SemiStem controller.

- Digital imaging with Gatan 676 TV rate image pickup system


Higher resolution instruments: www-em.materials.ox.ac.uk

www.begbrokenano.com



DRUG DELIVERY

CHITOSAN


Hydrogels represent an ideal class of polymeric material for various biomedical applications, including drug delivery, cell encapsulation and tissue engineering.
Thermosensitive hydrogels can be used as in situ forming implants. These biodegradable delivery systems are generally liquid formulations that form a semi-solid or solid depot after injection into the desired tissue or organ.

General advantages are localized or systemic prolonged drug delivery periods, drug dosage reduction along with reduction of undesirable side effects and reduced frequency of application. Besides theses advantages the application of in situ forming implants is less invasive and painful compared to common implants leading to an improved patient compliance and comfort.

Chitosan is an amino-polysaccharide obtained by alkaline deacetylation of chitin (exoskeleton of shrimps or crabs), with various biomedical applications. Chitosan is soluble in acidic solution and phase separates at pH > 6 to form a hydrogel. The addition of ß-glycerol-phosphate (ß-GP) to acidic chitosan solutions allows rising the pH to neutral without phase separation. These systems are thermosensitive and form hydrogels at temperature of 37°C and below. The sol-gel transition of these chitosan-ß-GP systems has been studied mainly by rheology.

To make these drug delivery systems accessible for poorly water soluble drugs, we developed an oil loaded chitosan hydrogel system. The aim of the present study was to optimize the composition of the gel to achieve sol-gel transition near body temperature and high oil content. To resolve the phase transition behaviour H-NMR relaxometry was used as an alternative method. Rheology methods widely used to characterize hydrogels are often time consuming, risking dehydration of the gels and report only on macroviscosity. Phase transitions can be observed due to the dependence of the dynamic of molecular groups to temperature. The NMR T relaxation time correlates to the dynamic viscosity as shown for Newtonian fluids and water mixtures of microcrystalline cellulose.



http://www.oxford-instruments.com/wps/wcm/resources/file/ebaf21001990ed8/Kempe-ParisECSBM2007.pdf