Effect of omega-3 fatty acids on crystallization, polymorphic transformation and stability of tripalmitin solid lipid nanoparticle suspensions

We examined the effect of lipid phase composition on the crystallization, polymorphic transition and stability of solid lipid nanoparticle (SLN) suspensions. A series of fine-disperse oil-in-water emulsions was prepared at an elevated temperature (75 °C) from a lipid phase containing different amounts of a high melting lipid (tripalmitin) and a low melting lipid (fish oil). These emulsions were cooled to induce crystallization and form SLN suspensions. In the absence of fish oil, the SLN suspensions formed a gel after the emulsified tripalmitin crystallized, which was attributed to particle shape changes leading to aggregation and network formation. Light scattering and rheology measurements indicated that incorporation of fish oil into the lipid phase (≥10 wt %) increased the stability of SLN to aggregation. DSC measurements suggested that crystallization, melting, and polymorphic transitions of SLN were influenced by the amount of fish oil incorporated. The rate of α- to β-polymorphic transitions of tripalmitin increased with increasing fish oil content, and tripalmitin crystals formed appeared to be less ordered as evidence by a lower melting temperature. Results suggest that the phase behavior and morphology of tripalmitin crystals can be altered by mixing them with low melting lipids such as fish oil thereby improving the stability of SLN suspensions to particle aggregation and gelation. Moreover, results show that fish oil, rich in ω-3 polyunsaturated fatty acids, can be successfully incorporated into SLN suspensions

Temperature Scanning Ultrasonic Velocity Study of Complex Thermal Transformations in Solid Lipid Nanoparticles

The purpose of this study was to determine whether temperature scanning ultrasonic velocity measurements could be used to monitor the complex thermal transitions that occur during the crystallization and melting of triglyceride solid lipid nanoparticles (SLNs). Ultrasonic velocity (u) measurements were compared with differential scanning calorimetry (DSC) measurements on tripalmitin emulsions that were cooled (from 75 to 5 °C) and then heated (from 5 to 75 °C) at 0.3 °C min−1. There was an excellent correspondence between the thermal transitions observed in δΔu/δT versus temperature curves determined by ultrasound and heat flow versus temperature curves determined by DSC. In particular, both techniques were sensitive to the complex melting behavior of the solidified tripalmitin, which was attributed to the dependence of the melting point of the SLNs on particle size. These studies suggest that temperature scanning ultrasonic velocity measurements may prove to be a useful alternative to conventional DSC techniques for monitoring phase transitions in colloidal systems

Effect of arginine on the aggregation of protein in freeze-dried Formulations containing sugars and polyol: 1-formulation development

L-arginine was introduced into protein-based freeze-dried formulations to study the ability of arginine to reduce/prevent from protein aggregation during manufacturing, storage and reconstitution of lyophilized protein-based pharmaceuticals. As L-arginine is known to be very hygroscopic, additional excipients which could provide a moisture buffering capacity need to be introduced into the formulation. In the first part of our study-excipient formulation development-the screening of a number of sugars/polyols has been done in order to select the best combination of excipients that, in a complex with L-arginine, can (i) produce freeze-dried cakes with elegant appearance, adequate mechanical properties and reconstitution times, and (ii) resist/minimise the moisture sorption. Various freeze-dried cakes containing L-arginine in combination with mannitol, trehalose, lactose and sucrose were produced and analysed by TGA, DSC, texture analysis, moisture sorption, cake shrinkage, TVIM and SEM. The non-linear dependencies of the physicochemical properties of the freeze-dried cakes on the sugar-to-mannitol ratios were found. The best combinations of excipients (L-arginine, mannitol and trehalose) were selected to be used in the second part of this work, in which the impact of each selected formulation will be studied in relation to the aggregation of a protein

Simple Chromatographic Method for Simultaneous Analyses of Phosphatidylcholine, Lysophosphatidylcholine, and Free Fatty Acids

This study describes a simple chromatographic method for the simultaneous analyses of phosphatidylcholine (PC) and its hydrolytic degradation products: lysophosphatidylcholine (LPC) and free fatty acids (FFA). Quantitative determination of PC, LPC, and FFA is essential in order to assure safety and to accurately assess the shelf life of phospholipid-containing products. A single-run normal-phase high-performance liquid chromatography (HPLC) with evaporative light scattering detector has been developed. The method utilizes an Allsphere silica analytical column and a gradient elution with mobile phases consisting of chloroform: chloroform–methanol (70:30%, v/v) and chloroform–methanol–water–ammonia (45:45:9.5:0.5%, v/v/v/v). The method adequately resolves PC, LPC, and FFA within a run time of 25 min. The quantitative analysis of PC and LPC has been achieved with external standard method. The free fatty acids were analyzed as a group using linoleic acid as representative standard. Linear calibration curves were obtained for PC (1.64–16.3 μg, r2 = 0.9991) and LPC (0.6–5.0 μg, r2 = 0.9966), while a logarithmic calibration curve was obtained for linoleic acid (1.1–5.8 μg, r2 = 0.9967). The detection and quantification limits of LPC and FFA were 0.04 and 0.1 μg, respectively. As a means of validating the applicability of the assay to pharmaceutical products, PC liposome was subjected to alkaline hydrolytic degradation. Quantitative HPLC analysis showed that 97% of the total mass balance for PC could be accounted for in liposome formulation. The overall results show that the HPLC method could be a useful tool for chromatographic analysis, stability studies, and formulation characterization of phospholipid-based pharmaceuticals