8 research outputs found
Using the Fluorescence Red Edge Effect to Assess the Long-Term Stability of Lyophilized Protein Formulations
Nanosecond
relaxation processes in sugar matrices are causally
linked through diffusional processes to protein stability in lyophilized
formulations. Long-term protein degradation rates track mean-squared
displacement (⟨<i>u</i><sup>2</sup>⟩) of hydrogen
atoms in sugar glasses, a parameter describing dynamics on a time
scale of picoseconds to nanoseconds. However, measurements of ⟨<i>u</i><sup>2</sup>⟩ are usually performed by neutron scattering,
which is not conducive to rapid formulation screening in early development.
Here, we present a benchtop technique to derive a ⟨<i>u</i><sup>2</sup>⟩ surrogate based on the fluorescence
red edge effect. Glycerol, lyophilized trehalose, and lyophilized
sucrose were used as model systems. Samples containing 10<sup>–6</sup> mole fraction of rhodamine 6G, a fluorophore, were excited at either
532 nm (main peak) or 566 nm (red edge), and the ⟨<i>u</i><sup>2</sup>⟩ surrogate was determined based the corresponding
Stokes shifts. Results showed reasonable agreement between ⟨<i>u</i><sup>2</sup>⟩ from neutron scattering and the surrogate
from fluorescence, although deviations were observed at very low temperatures.
We discuss the sources of the deviations and suggest technique improvements
to ameliorate these. We expect that this method will be a valuable
tool to evaluate lyophilized sugar matrices with respect to their
ability to protect proteins from diffusion-limited degradation processes
during long-term storage. Additionally, the method may have broader
applications in amorphous pharmaceutical solids
Surrogate for Debye–Waller Factors from Dynamic Stokes Shifts
We show that the short-time behavior of time-resolved fluorescence Stokes shifts (TRSS) are similar to that of the intermediate scattering function obtained from neutron scattering at <i>q</i> near the peak in the static structure factor for glycerol. This allows us to extract a Debye–Waller (DW) factor analogue from TRSS data at times as short as 1 ps in a relatively simple way. Using the time domain relaxation data obtained by this method, we show that DW factors evaluated at times ≥ 40 ps can be directly influenced by α relaxation and thus should be used with caution when evaluating relationships between fast and slow dynamics in glass-forming systems
Imaging the Molecular Structure of Polyethylene Blends with Broadband Coherent Raman Microscopy
Polyethylene (PE) has been widely used in a myriad of
consumer
products and critical infrastructure products such as underground
gas and water pipes. These products are often made of blends of multiple
types of PE with different molecular architectures. Although the long-term
performance of these products is largely dictated by their local molecular
structure, it has been studied mostly by indirect and bulk-averaging
methods such as calorimetry and neutron scattering due to lack of
chemical contrast for conventional imaging techniques. We demonstrate
that broadband coherent anti-Stokes Raman scattering (CARS) microscopy
can acquire images of the chemical composition and molecular orientation
of a miscible semicrystalline PE blend with two different molecular
architectures. We discuss the detailed crystal structure observed
at different length scales and new insights it provides into polymer
crystal morphology
Enhanced Stabilization in Dried Silk Fibroin Matrices
Preliminary studies
have shown that silk fibroin can protect biomacromolecules
from thermal degradation, but a deeper understanding of underlying
mechanisms needed to fully leverage the stabilizing potential of this
matrix has not been realized. In this study, we investigate stabilization
of plasma C-reactive protein (CRP), a diagnostic indicator of infection
or inflammation, to gain insight into stabilizing mechanisms of silk.
We observed that the addition of antiplasticizing excipients that
suppress β-relaxation amplitudes in silk matrices resulted in
enhanced stability of plasma CRP. These observations are consistent
with those made in sugar-glass-based protein-stabilizing matrices
and suggest fundamental insight into mechanisms as well as practical
strategies to employ with silk protein matrices for enhanced stabilization
utility
DataSheet2_Identifying lipid particle sub-types in live Caenorhabditis elegans with two-photon fluorescence lifetime imaging.pdf
Fat metabolism is an important modifier of aging and longevity in Caenorhabditis elegans. Given the anatomy and hermaphroditic nature of C. elegans, a major challenge is to distinguish fats that serve the energetic needs of the parent from those that are allocated to the progeny. Broadband coherent anti-Stokes Raman scattering (BCARS) microscopy has revealed that the composition and dynamics of lipid particles are heterogeneous both within and between different tissues of this organism. Using BCARS, we have previously succeeded in distinguishing lipid-rich particles that serve as energetic reservoirs of the parent from those that are destined for the progeny. While BCARS microscopy produces high-resolution images with very high information content, it is not yet a widely available platform. Here we report a new approach combining the lipophilic vital dye Nile Red and two-photon fluorescence lifetime imaging microscopy (2p-FLIM) for the in vivo discrimination of lipid particle sub-types. While it is widely accepted that Nile Red staining yields unreliable results for detecting lipid structures in live C. elegans due to strong interference of autofluorescence and non-specific staining signals, our results show that simple FLIM phasor analysis can effectively separate those signals and is capable of differentiating the non-polar lipid-dominant (lipid-storage), polar lipid-dominant (yolk lipoprotein) particles, and the intermediates that have been observed using BCARS microscopy. An advantage of this approach is that images can be acquired using common, commercially available 2p-FLIM systems within about 10% of the time required to generate a BCARS image. Our work provides a novel, broadly accessible approach for analyzing lipid-containing structures in a complex, live whole organism context.</p
DataSheet1_Identifying lipid particle sub-types in live Caenorhabditis elegans with two-photon fluorescence lifetime imaging.ZIP
Fat metabolism is an important modifier of aging and longevity in Caenorhabditis elegans. Given the anatomy and hermaphroditic nature of C. elegans, a major challenge is to distinguish fats that serve the energetic needs of the parent from those that are allocated to the progeny. Broadband coherent anti-Stokes Raman scattering (BCARS) microscopy has revealed that the composition and dynamics of lipid particles are heterogeneous both within and between different tissues of this organism. Using BCARS, we have previously succeeded in distinguishing lipid-rich particles that serve as energetic reservoirs of the parent from those that are destined for the progeny. While BCARS microscopy produces high-resolution images with very high information content, it is not yet a widely available platform. Here we report a new approach combining the lipophilic vital dye Nile Red and two-photon fluorescence lifetime imaging microscopy (2p-FLIM) for the in vivo discrimination of lipid particle sub-types. While it is widely accepted that Nile Red staining yields unreliable results for detecting lipid structures in live C. elegans due to strong interference of autofluorescence and non-specific staining signals, our results show that simple FLIM phasor analysis can effectively separate those signals and is capable of differentiating the non-polar lipid-dominant (lipid-storage), polar lipid-dominant (yolk lipoprotein) particles, and the intermediates that have been observed using BCARS microscopy. An advantage of this approach is that images can be acquired using common, commercially available 2p-FLIM systems within about 10% of the time required to generate a BCARS image. Our work provides a novel, broadly accessible approach for analyzing lipid-containing structures in a complex, live whole organism context.</p
Pronounced Microheterogeneity in a Sorbitol–Water Mixture Observed through Variable Temperature Neutron Scattering
In this study, the structure of concentrated d-sorbitol–water
mixtures is studied by wide- and small-angle neutron scattering (WANS
and SANS) as a function of temperature. The mixtures are prepared
using both deuterated and regular sorbitol and water at a molar fraction
of sorbitol of 0.19 (equivalent to 70% by weight of regular sorbitol
in water). Retention of an amorphous structure (i.e., absence of crystallinity)
is confirmed for this system over the entire temperature range, 100–298
K. The glass transition temperature, Tg, is found from differential
scanning calorimetry to be approximately 200 K. WANS data are analyzed
using empirical potential structure refinement, to obtain the site–site
radial distribution functions (RDFs) and coordination numbers. This
analysis reveals the presence of nanoscaled water clusters surrounded
by (and interacting with) sorbitol molecules. The water clusters appear
more structured compared to bulk water and, especially at the lowest
temperatures, resemble the structure of low-density amorphous ice
(LDA). Upon cooling to 100 K the peaks in the water RDFs become markedly
sharper, with increased coordination number, indicating enhanced local
(nanometer-scale) ordering, with changes taking place both above and
well below the Tg. On the mesoscopic (submicrometer) scale, although
there are no changes between 298 and 213 K, cooling the sample to
100 K results in a significant increase in the SANS signal, which
is indicative of pronounced inhomogeneities. This increase in the
scattering is partly reversed during heating, although some hysteresis
is observed. Furthermore, a power law analysis of the SANS data indicates
the existence of domains with well-defined interfaces on the submicrometer
length scale, probably as a result of the appearance and growth of
microscopic voids in the glassy matrix. Because of the unusual combination
of small and wide scattering data used here, the present results provide
new physical insight into the structure of aqueous glasses over a
broad temperature and length scale, leading to an improved understanding
of the mechanisms of temperature- and water-induced (de)Âstabilization
of various systems, including proteins, pharmaceuticals, and biological
objects
Multicomponent Chemical Imaging of Pharmaceutical Solid Dosage Forms with Broadband CARS Microscopy
We
compare a coherent Raman imaging modality, broadband coherent
anti-Stokes Raman scattering (BCARS) microscopy, with spontaneous
Raman microscopy for quantitative and qualitative assessment of multicomponent
pharmaceuticals. Indomethacin was used as a model active pharmaceutical
ingredient (API) and was analyzed in a tabulated solid dosage form,
embedded within commonly used excipients. In comparison with wide-field
spontaneous Raman chemical imaging, BCARS acquired images 10×
faster, at higher spatiochemical resolution and with spectra of much
higher SNR, eliminating the need for multivariate methods to identify
chemical components. The significant increase in spatiochemical resolution
allowed identification of an unanticipated API phase that was missed
by the spontaneous wide-field method and bulk Raman spectroscopy.
We confirmed the presence of the unanticipated API phase using confocal
spontaneous Raman, which provided spatiochemical resolution similar
to BCARS but at 100× slower acquisition times