Protein-based therapeutics are used to treat or prevent a range of diseases, but a challenge for the expanded use of these products is the need for cold storage that makes distribution difficult in low-resource settings. Lyophilization is a common method used to stabilize protein-based products. However, this process remains expensive, and many freeze-dried proteins require cold-chain storage. Anhydrous preservation in an amorphous trehalose matrix has been successfully used as an alternative to lyophilization. A new processing technique called light assisted drying (LAD) has been used to successfully dry proteins in preparation for anhydrous storage. Water is selectively heated via near-infrared (1064 nm) illumination, rapidly removing water from a sample, and forming an amorphous matrix that can be stored at supra-zero temperatures. In previous work, large volume samples (0.25 ml) were successfully LAD processed on glass coverslips, but this substrate is not typically used in industry. In this study, large volume samples are LAD processed in vials that are commonly used to lyophilize vaccines. After LAD processing, the samples are stored at room temperature (20◦C) or refrigerated (4◦C) for one month. The end moisture content of samples was determined immediately after processing/storage to evaluate the effectiveness of water removal via LAD. The trehalose matrix was characterized using polarized light imaging to determine if crystallization occurred during storage, potentially damaging embedded proteins. These preliminary studies indicate that LAD can effectively stabilize large volume samples in glass lyophilization vials and demonstrates the potential use of LAD to stabilize products such as vaccines.
Enhanced Thermal Imaging (ETI) is a new thermal infrared (8-10 μm) imaging technique that delineates blood vessels embedded in water-rich tissue in real time. ETI uses selective heating of blood via illumination with a green (532 nm) LED to produce a thermal contrast (∼ 0.5°C) between blood vessels and surrounding water-rich tissue. The warmer blood vessels appear brighter in the thermal image. In a previous study, the growth of breast cancer tumors in an 4T1 murine orthotopic model was successfully monitored in vivo using ETI. The images highlighted regions that are routinely targeted for surgical excision around solid mass tumors. Recently, improvements to the acquisition software have enabled real-time imaging with this technique, highlighting ETI’s potential use as an intraoperative imaging tool. In this study, simulations of direct illumination and heating of the blood vessels embedded in tissue were conducted to understand the effects of LED power and vessel depth on the ability of ETI to detect vascular structures. The simulations were performed with an open-source MATLAB integrated solver, MCmatlab.
Cold-chain storage can be challenging and expensive for the transportation and storage of biologics, especially in low-resource settings. Recent research has demonstrated that anhydrous preservation in a trehalose amorphous solid matrix offers an alternative to freeze drying for the preservation of biologics. We have previously described a new processing technique, light assisted drying (LAD), to create trehalose preservation matrices of small volume (40 μL) samples. LAD uses illumination by near-infrared laser light to selectively heat water and speed dehydration. In this study we apply the LAD technique to large volume samples (250 μL) that are more comparable to therapeutic doses.
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