Anasys enables point and click local thermal analysis
thermal analyser which promises to help pharmaceutical companies'
quality control (QC) of drug coatings and formulations.
The new instrument, the Vesta, enables users to identify surface features of interest using an optical microscope before using the heated probe to perform local thermal analysis (TA) that allows a user to determine the temperature a specific area of a substance goes through a phase transition (such as melting). Thermal analysis has traditionally been used to study bulk materials, with Differential Scanning Calorimetry (DSC) being one of the most commonly used techniques. While this has been very useful for studying bulk materials, it only generates an average thermal response curve for an entire sample, limiting its applicability to studying complex formulations and layered materials such as the coatings on drug tablets. "Coatings have traditionally been studied using complex tools such as IR [infra red] and Raman spectroscopy, but this quick optical microscope-based thermal analysis method makes coating analysis much easier," said Roshan Shetty, CEO of Anasys. According to a review published in the Journal of Pharmaceutical Sciences, the micro-TA "has the potential ability to not only discriminate between different materials, or indeed physical forms [of a compound such as polymorphs] within a multicomponent system, but also the ability… to perform characterisation studies." The review continues by stressing how important this could be as the majority of solid-state dosage forms are composite formulations. "One of the potential applications for the Vesta is studying coatings and checking there are no imperfections that could lead to faster than desired drug release," said Shetty The technology used in the Vesta, derives from Anasys' expertise in nano-thermal analysis instruments which combines the high spatial resolution imaging capabilities of atomic force microscopy (AFM) with the ability to obtain an understanding of the thermal behaviour of specified areas of the material. The innovation that enabled 'scanning thermal microscopy' was the replacement of a conventional AFM probe with a thermal probe that allows a controlled heating signal to be applied to a highly specific region. These probes were traditionally Woolaston wires, however these had a tendency to bend and Anasys has overcome this problem by developing and commercialising an alternative in its micro-machined silicon probes that can have a radius as small as 20nm. The company's 2007 R&D100 award winning nano-TA probes can be used with any AFM enabling the analysis of areas at a resolution of 50nm, a spatial resolution that was 50 times that of the previous state of the art instruments. However, while this is a great option for research orientated studies, because the technique is based within an AFM, users had to be trained electron microscopists. "The traditional complexity with nano-TA was associated with acquiring the AFM image and interpreting it," said Shetty. "The Vesta is configured to be a push button instrument; you just look at the image of the sample, identify a feature and click to run the thermal analysis." Because the Vesta uses an optical microscope, loading samples and acquiring image data is much faster than if an AFM were being used. In addition, because the thermal probe is retained from the nano-TA instrument, the spatial resolution (although not the image resolution) is retained. It is also much easier to train users on, with Shetty predicting that it would take less than a day to train a new user who was completely unfamiliar to thermal analysis. In contrast, training someone to use (and maintain) an AFM takes a considerable amount of time.
