ANALYTICAL AND LABORATORY EQUIPMENT 5
To introduce this powerful technique, the company has published an in-depth paper that explains the background to microrheology, and how it can be used to investigate the rheological properties of even the most weakly structured fluids, using sample volumes on the microliter scale. An ‘Introduction to DLS Microrheology’ includes data for protein (bovine serum albumin (BSA)) and polyethylene oxide (PEO) solutions that illustrate the significance and usefulness of the method. See:
www.malvern.com/ DLS-Microrheology-paper.
Microrheology is a relatively new analytical methodology that has been the subject of increasing academic study over the past 15 years, and is of growing interest to those researchers working at the forefront of rheological characterisation. It involves tracking the motion of colloidal tracer particles dispersed in a complex fluid sample, in order to extract the viscoelastic properties of the system.
DLS Microrheology has attributes that are particularly advantageous for characterising low viscosity samples, such as polymer or protein solutions, and extends the measurement range and application of rheology well beyond the regimes accessible with even the most sophisticated mechanical rheometers.
A central advantage is that it can access the very high frequencies, or short timescale measurements, that are needed to characterise these weakly structured fluids.
Furthermore, data can be obtained with very small sample volumes so the technique is well-suited to the analysis of high value protein solutions, for example.
‘An Introduction to DLS Microrheology’ provides a general overview of microrheology techniques, before going on to focus
Fig. 3. The Morphologi G3-ID particle characterisation system from Malvern Instruments.
www.scientistlive.com
on DLS Microrheology and the underlying theory. Practical aspects of microrheology are discussed in some detail, with guidance on method development and sample preparation, both of which are particularly important factors for robust measurements. Te paper concludes with some experimental data that demonstrate applicability.
solution characterisation.
Te results indicate that the development of solution viscoelasticity can be used to investigate the onset of protein aggregation in denaturing BSA solutions, as well as assessing solution viscosity as a function of concentration to determine onset of non-Newtonian flow properties.
Meanwhile, following the completion of an early access programme, Malvern Instruments has launched the Morphologi G3-ID particle characterisation system to the global market.
Fig. 2. Malvern’s new Zetasizer Nano ZSP makes the technique of DLS Microrheology accessible to a more laboratories.
Tese data show how DLS Microrheology, combined with conventional rotational rheology, can significantly extend the measured viscoelastic spectrum for polymer solutions for characterisation of short timescale dynamics, and demonstrate its value for protein
Te system combines automated particle imaging with the chemical identification of individual particles using Raman spectroscopy. Tis fully automated system measures particle size, shape and chemical identity in a single platform.
Te Morphologi G3-ID (Fig. 3) is suited to solving complex particle characterisation problems where particle size and shape do not provide sufficient information.
Te recent early access programme was designed to enable users to explore specific applications and
to allow full optimisation of the product features.
Key applications for which it is proving especially valuable are in determining component-specific particle properties of mixtures and blends, such as the particle size of drug ingredients in nasal sprays and asthma inhalers, and in the identification of unknown or suspicious particles in injectable or parenteral products, for example.
Te Morphologi G3-ID is designed to meet a wide variety of needs and to enable all users, from particle characterisation scientists with limited spectroscopy experience right through to experienced spectroscopists, to gain an in-depth understanding of particulate samples. Simple SOP operation takes the user from integrated sample dispersion for dry powders through to size, shape and chemical analysis, with automatic selection, targeting and chemical classification of thousands of individual particles. Measurements can be made on dry powders, suspensions and membrane filters.
For more information, visit
www.biopharma.novozymes.com or
www.malvern.com
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