In this work, we demonstrate the enhanced thermal and steric stability of lipid-based formulations in the presence of encapsulated HPPH that have demonstrated potential cancer applications in previously presented in vivo studies. Differential scanning calorimeter (DSC) was used to study the phase transitions, and domain formations, and to qualify the thermodynamic properties associated with change in lipid bilayer behavior due to the presence of PEGylated at varying concentrations and sizes, and the encapsulated HPPH molecules. Thermal instability was quantified by dramatic changes in calculated enthalpy, and the shape of the melting peak or calculated half width of melting peak. This systematic study focused on understanding the effects of varying molecular mass and concentrations of PEG polymers in the photopolymerizable lipid DC
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PC lipid bilayer matrix for four weeks at room temperature of 25 °C. The major findings include increased thermal stability of the lipid bilayer due to the presence of PEG-2 K and the HPPH that resulted from the van der Waals forces between various molecular species, and the change in bilayer curvature confirmed via mathematical correlations. It is demonstrated that the encapsulation of therapeutics in lipid formulations can alter their overall thermal behavior, and therefore, it is imperative to consider calorimetric effects while designing lipid-based vaccines. The presented research methodologies and findings presented can predict the stability of lipid-based vaccines that are under development such as COVID-19 during their storage, transport, and distribution.
PEGylation is a well-established strategy for improving the target specificity, circulation time and stability of liposomes, thereby improving their stealth properties. This brief review provides an insight on the composition of PEGylated liposomes and the characteristics that dictate the functionality of PEGylated liposomes such as surface density, molecular weight, presence of linkers and acyl groups. Physicochemical techniques used to characterize the PEG liposomes and test their stability are also discussed along with their clinical implications. This review provides the readers with a broad range of understanding of various PEGylated lipids, techniques to access their stability in liposomal formulations and state-of -the-art development of PEGylated liposomal formulations.
Riboflavin presents tremendous potential as a photosensitizing agent for photodynamic therapy (PDT) for treating microbial infection and cancer therapy. Encapsulation of riboflavin can improve its bioavailability and stability while making the clinical applications more efficient. The authors' detailed study on cellular inhibition of liposome encapsulated riboflavin-5-phosphate investigation, and the effect of unencapsulated riboflavin on liposome bilayers aims to improve the efficiency of cellular delivery of riboflavin. Nano-sized liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol were used in this study. Cell studies demonstrate high inhibition rates for the lipsome-encapsualted high concentration riboflavin formulations in the presence of blue light, despite the lower encapsulation lading.
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