Cristina Torrisi

Solid lipid nanoparticles (SLNs) are lipid-based colloidal systems used for the delivery of active compounds. Although SLNs have many benefits, they show important issues due to physical and chemical instability phenomena during storage. For these reasons, it is highly desirable to have a dried SLN formulation available. Therefore, the aim of the project was to identify suitable methods to obtain a dry powder formulation from an SLN suspension. The nanoparticle suspension was dried using both freeze- and spray-drying techniques. The suitability of these methods in obtaining SLN dry powders was evaluated from the analyses of nanotechnological parameters, system morphology and thermal behavior using differential scanning calorimetry. Results pointed out that both drying techniques, although at different yields, were able to produce an SLN dry powder suitable for pharmaceutical applications. Noteworthily, the freeze-drying of SLNs under optimized conditions led to a dry powder endowed with good reconstitution properties and technological parameters similar to the starting conditions. Moreover, freeze–thaw cycles were carried out as a pretest to study the protective effect of different cryoprotectants (e.g., glucose and mannitol with a concentration ranging from 1% to 10% w/v). Glucose proved to be the most effective in preventing particle growth during freezing, thawing, and freeze-drying processes; in particular, the optimum concentration of glucose was 1% w/v.

Colorectal cancer is one of the most diffused tumoral diseases. Since most medicaments employed for its treatment are debilitating, the use of naturally derived products, which can be effective against the mutated cells and, in addition, can reduce most inflammatory-related effects, could be extremely beneficial for the continued treatment of this disease. In this research, ethyl protocatechuate (PCAEE), a protocatechuic acid prodrug, was encapsulated in solid lipid nanoparticles (SLN) (prepared without and with Tween 80), which were characterized in terms of size, polydispersity index (PDI), zeta potential and thermotropic behavior. Encapsulation efficiency, release profile and interaction with a model of biomembrane were also assessed. The nanoparticles were tested in vitro on both healthy cells and on a model of tumoral cells. SLN prepared with Tween 80 was promising in terms of physicochemical properties (z-average of 190 nm, PDI 0.150 and zeta potential around −20 mV) and encapsulation efficiency (56%); they showed a desirable release profile, demonstrated an ability to penetrate and release the encapsulated PCAEE into a biomembrane model and were nontoxic on healthy cells. In addition, they caused a greater dose-dependent decrease in the viability of CaCo-2 cells than PCAEE alone. In conclusion, the formulation could be proposed for further studies to assess its suitability for the treatment of colorectal cancer.

Investigation of the interaction between drugs and biomembrane models, as a strategy to study and eventually improve drug/substrate interactions, is a crucial factor in preliminary screening. Synthesized peptides represent a source of potential anticancer and theragnostic drugs. In this study, we investigated the interaction of a novel synthesized peptide, called RH-23, with a simplified dimyristoylphosphatidylcholine (DMPC) model of the cellular membrane. The interaction of RH-23 with DMPC, organized either in multilamellar vesicles (MLVs) and in Langmuir-Blodgett (LB) monolayers, was assessed using thermodynamic techniques, namely differential scanning calorimetry (DSC) and LB. The calorimetric evaluations showed that RH-23 inserted into MLVs, causing a stabilization of the phospholipid gel phase that increased with the molar fraction of RH-23. Interplay with LB monolayers revealed that RH-23 interacted with DMPC molecules. This work represents the first experimental thermodynamic study on the interaction between RH-23 and a simplified model of the lipid membrane, thus providing a basis for further evaluations of the effect of RH-23 on biological membranes and its therapeutic/diagnostic potential.

Skin is the first human barrier that is daily exposed to a broad spectrum of physical and chemical agents, which can increase reactive oxygen species (ROS) and lead to the formation of topical disorders. Antioxidant molecules, such as benzo[k,l]xanthene lignans (BXL), are ideal candidates to eliminate or minimize the effects of ROS. Herein, we aimed to formulate BXL-loaded solid lipid nanoparticles (SLN-BXL) to improve the bioavailability and interaction with the skin, and also to investigate the protective impact against intracellular ROS generation in HFF-1 in comparison with the drug-free situation. SLN-BXL were formulated using the PIT/ultrasonication method, and then were subjected to physicochemical characterizations, i.e., average size, zeta potential (ZP), polydispersity index (PDI), encapsulation efficiency (%EE), thermotropic behavior, and interaction with a biomembrane model. The results show a mean size around 200 nm, PDI of 0.2, and zeta potential of about −28 mV, with values almost unchanged over a period of three months, while the EE% is ≈70%. Moreover, SLN-BXL are able to deeply interact with the biomembrane model, and to achieve a double-action release in mildly hydrophobic matrices; the results of the in vitro experiments confirm that SLN-BXL are cell-safe and capable of attenuating the IL-2-induced high ROS levels. In conclusion, based on our findings, the formulation can be proposed as a candidate for a preventive remedy against skin disorders induced by increased levels of ROS.

Benzo[k,l]xanthene lignans are a group of rare natural products belonging to the class of polyphenols with promising biological activities and are studied as potential chemotherapeutic agents. The lipophilic character of a xanthene core makes these molecules difficult to be used in an aqueous medium, limiting their employment in studies for pharmaceutical applications. To overcome this problem, a drug-delivery system which is able to improve the stability and bioavailability of the compound can be used. In this study, a bioactive benzoxanthene lignan (BXL) has been included in SLN. Unloaded and BXL-loaded SLN have been prepared using the Phase Inversion Temperature method and characterized in terms of size, zeta potential, entrapment efficiency and stability. Differential scanning calorimetry was used to evaluate the thermotropic behavior and ability of SLN to act as carriers for BXL. A biomembrane model, represented by multilamellar vesicles, was used to simulate the interaction of the SLN with the cellular membrane. Unloaded and loaded SLN were incubated with the MLV, and their interactions were evaluated through variations in their calorimetric curves. The results obtained suggest that SLN could be used as a delivery system for BXL.

The interactions of drugs with cell membranes are of primary importance for several processes involved in drugs activity. However, these interactions are very difficult to study due to the complexity of biological membranes. Lipid model membranes have been developed and used to gain insight into drug–membrane interactions. In this study, the interaction of protocatechuic acid ethyl ester, showing radical-scavenging activity, antimicrobial, antitumor and anti-inflammatory effects, with model membranes constituted by multilamellar vesicles and monolayers made of DMPC and DSPC, has been studied. Differential scanning calorimetry and Langmuir–Blodgett techniques have been used. Protocatechuic acid ethyl ester interacted both with MLV and monolayers. However, a stronger interaction of the drug with DMPC-based model membranes has been obtained. The finding of this study could help to understand the protocatechuic acid ethyl ester action mechanism.

Naringenin (4′,5,7-trihydroxyflavanone-7-rhamnoglucosideor naringenin-7-rhamnoglucoside), a flavonoid present in large quantities in citrus, has different beneficial effects on human health as an antioxidant, free radical scavenger, anti-inflammatory, carbohydrate metabolism promoter, and immune system modulator. Different studies have shown that this substance also has a hypoglycemic and antihypertensive effect, reduces cholesterol and triglycerides, and plays an important protective role in the heart tissue; moreover, it provides neuroprotection against various neurological disorders such as Parkinson’s disease and unpredictable chronic stress-induced depression. Despite these advantages, Naringenin is poorly absorbed, and the small percentage absorbed is rapidly degraded by the liver, as a result losing its activity. Several approaches have been attempted to overcome these obstacles, among them, nanotechnology, with the use of Drug Delivery Systems (DDS) as Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC). DDS can, in fact, improve the drug bioavailability. The aim of this study was to develop and characterize SLN and NLC containing Naringenin and to evaluate the ability of these nanoparticles to release Naringenin at the cell level using biomembrane models represented by Multilamellar Vesicles (MLV). These studies were performed using Differential Scanning Calorimetry, a powerful technique to detect the interaction of drugs and delivery systems with MLV. It was shown that Naringenin could be better incorporated into NLC with respect to SLN and that Naringenin could be released by NLC into the biomembrane model. Therefore, suggesting the administration of Naringenin loaded into nanoparticles could help avoid the disadvantages associated with the use of the free molecule.

Sinapic acid (SA), belonging to the phenylpropanoid family, and its derivatives are secondary metabolites found in the plant kingdom. In recent years, they have drawn attention because of their various biological activities, including neuroprotective effects. In this study, SA was incorporated into two different nanoparticle systems, solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC). The influence of different concentrations of SA on the nanoparticle systems was evaluated. It was studied the efficacy of the nanoparticle systems to release the active ingredient at cell level through the use of models of biological membranes represented by multilamellar vesicles (MLV) of dimyristoylphosphatidylcholine (DMPC) and conducting kinetic studies by placing in contact SLN and NLC, both unloaded and loaded with two different amounts of SA, with the same biological membrane model. Differential scanning calorimetry (DSC) was used for these studies. The results indicated a different distribution of SA within the two nanoparticle systems and that NLC are able to incorporate and release SA inside the structure of the biological membrane model.

Several liquid lipids have been proposed to obtain nanostructured lipid carriers (NLC) with improved efficiency. An attractive strategy is the use of oils that could elicit a synergic effect with the loaded drug. In this work, different percentages (0–4% w/w) of tocopheryl acetate (TA), an oily antioxidant, were used as liquid lipid to prepare NLC loading idebenone (IDE), a synthetic antioxidant investigated for the treatment of neurodegenerative and topical diseases. The technological properties of such NLC were evaluated, as well as the interactions among lipid core components. Loading different percentages of IDE (1–4% w/w) into NLC containing TA up to 4% w/w, no significant change of mean size and polydispersity index was observed. IDE loading capacity was 4% w/w but NLC containing IDE percentages greater than 1.5% w/w showed poor stability during long-term storage. Differential scanning calorimetry analyses highlighted linear relationships between peak temperature and TA percentages, while the enthalpy variation and recrystallization index values showed that increasing the percentage of TA led to less crystalline structure of the NLC core. Therefore, NLC co-loading IDE and TA could be useful to design new delivery systems for the treatment of diseases that could benefit from the co-administration of these antioxidants.