Enhanced anti-hyperproliferative activity of human thymidylate synthase inhibitor peptide by solid lipid nanoparticle delivery

Solid Lipid Nanoparticles vs. Nanostructured Lipid Carriers: A Comparative Review

Solid-lipid nanoparticles and nanostructured lipid carriers are delivery systems for the delivery of drugs and other bioactives used in diagnosis, therapy, and treatment procedures. These nanocarriers may enhance the solubility and permeability of drugs, increase their bioavailability, and extend the residence time in the body, combining low toxicity with a targeted delivery. Nanostructured lipid carriers are the second generation of lipid nanoparticles differing from solid lipid nanoparticles in their composition matrix. The use of a liquid lipid together with a solid lipid in nanostructured lipid carrier allows it to load a higher amount of drug, enhance drug release properties, and increase its stability. Therefore, a direct comparison between solid lipid nanoparticles and nanostructured lipid carriers is needed. This review aims to describe solid lipid nanoparticles and nanostructured lipid carriers as drug delivery systems, comparing both, while systematically elucidating their production methodologies, physicochemical characterization, and in vitro and in vivo performance. In addition, the toxicity concerns of these systems are focused on.

Design, Characterization, and In Vitro Assays on Muscle Cells of Endocannabinoid-like Molecule Loaded Lipid Nanoparticles for a Therapeutic Anti-Inflammatory Approach to Sarcopenia

Inflammatory processes play a key role in the pathogenesis of sarcopenia owing to their effects on the balance between muscle protein breakdown and synthesis. Palmitoylethanolamide (PEA), an endocannabinoid-like molecule, has been well documented for its anti-inflammatory properties, suggesting its possible beneficial use to counteract sarcopenia. The promising therapeutic effects of PEA are, however, impaired by its poor bioavailability. In order to overcome this limitation, the present study focused on the encapsulation of PEA in solid lipid nanoparticles (PEA-SLNs) in a perspective of a systemic administration. PEA-SLNs were characterized for their physico-chemical properties as well as cytotoxicity and cell internalization capacity on C2C12 myoblast cells. Their size was approximately 250 nm and the encapsulation efficiency reached 90%. Differential scanning calorimetry analyses demonstrated the amorphous state of PEA in the inner SLN matrix, which improved PEA dissolution, as observed in the in vitro assays. Despite the high internalization capacity observed with the flow cytometer (values between 85 and 94% after 14 h of incubation), the Nile Red labeled PEA-SLNs showed practically no toxicity towards myoblasts. Confocal analysis showed the presence of SLNs in the cytoplasm and not in the nucleus. These results suggest the potentiality provided by PEA-SLNs to obtain an innovative and side-effect-free tool in the medical treatment of sarcopenia.

Particle engineering principles and technologies for pharmaceutical biologics

The global market of pharmaceutical biologics has expanded significantly during the last few decades. Currently, pharmaceutical biologic products constitute an indispensable part of the modern medicines. Most pharmaceutical biologic products are injections either in the forms of solutions or lyophilized powders because of their low oral bioavailability. There are certain pharmaceutical biologic entities formulated into particulate delivery systems for the administration via non-invasive routes or to achieve prolonged pharmaceutical actions to reduce the frequency of injections. It has been well documented that the design of nano- and microparticles via various particle engineering technologies could render pharmaceutical biologics with certain benefits including improved stability, enhanced intracellular uptake, prolonged pharmacological effect, enhanced bioavailability, reduced side effects, and improved patient compliance. Herein, we review the principles of the particle engineering technologies based on bottom-up approach and present the important formulation and process parameters that influence the critical quality attributes with some mathematical models. Subsequently, various nano- and microparticle engineering technologies used to formulate or process pharmaceutical biologic entities are reviewed. Lastly, an array of commercialized products of pharmaceutical biologics accomplished based on various particle engineering technologies are presented and the challenges in the development of particulate delivery systems for pharmaceutical biologics are discussed.

Folic Acid-Peptide Conjugates Combine Selective Cancer Cell Internalization with Thymidylate Synthase Dimer Interface Targeting

Drug-target interaction, cellular internalization, and target engagement should be addressed to design a lead with high chances of success in further optimization stages. Accordingly, we have designed conjugates of folic acid with anticancer peptides able to bind human thymidylate synthase (hTS) and enter cancer cells through folate receptor α (FRα) highly expressed by several cancer cells. Mechanistic analyses and molecular modeling simulations have shown that these conjugates bind the hTS monomer-monomer interface with affinities over 20 times larger than the enzyme active site. When tested on several cancer cell models, these conjugates exhibited FRα selectivity at nanomolar concentrations. A similar selectivity was observed when the conjugates were delivered in synergistic or additive combinations with anticancer agents. At variance with 5-fluorouracil and other anticancer drugs that target the hTS catalytic pocket, these conjugates do not induce overexpression of this protein and can thus help combating drug resistance associated with high hTS levels.

A Peptidic Thymidylate-Synthase Inhibitor Loaded on Pegylated Liposomes Enhances the Antitumour Effect of Chemotherapy Drugs in Human Ovarian Cancer Cells

There is currently no effective long-term treatment for ovarian cancer (OC) resistant to poly-chemotherapy regimens based on platinum drugs. Preclinical and clinical studies have demonstrated a strong association between development of Pt-drug resistance and increased thymidylate synthase (hTS) expression, and the consequent cross-resistance to the hTS inhibitors 5-fluorouracil (5-FU) and raltitrexed (RTX). In the present work, we propose a new tool to combat drug resistance. We propose to treat OC cell lines, both Pt-sensitive and -resistant, with dual combinations of one of the four chemotherapeutic agents that are widely used in the clinic, and the new peptide, hTS inhibitor, [D-Gln⁴]LR. This binds hTS allosterically and, unlike classical inhibitors that bind at the catalytic pocket, causes cell growth inhibition without inducing hTS overexpression. The dual drug combinations showed schedule-dependent synergistic antiproliferative and apoptotic effects. We observed that the simultaneous treatment or 24h pre-treatment of OC cells with the peptide followed by either agent produced synergistic effects even in resistant cells. Similar synergistic or antagonistic effects were obtained by delivering the peptide into OC cells either by means of a commercial delivery system (SAINT-PhD) or by pH sensitive PEGylated liposomes. Relative to non-PEGylated liposomes, the latter had been previously characterized and found to allow macrophage escape, thus increasing their chance to reach the tumour tissue. The transition from the SAINT-PhD delivery system to the engineered liposomes represents an advancement towards a more drug-like delivery system and a further step towards the use of peptides for in vivo studies. Overall, the results suggest that the association of standard drugs, such as cDDP and/or 5-FU and/or RTX, with the novel peptidic TS inhibitor encapsulated into PEGylated pH-sensitive liposomes can represent a promising strategy for fighting resistance to cDDP and anti-hTS drugs.

pH responsible and fluorescent Cy5.5-PEG-g-A-HA/CDDP complex nanoparticles: synthesis, characterization, and application for targeted drug delivery

Clinical application of cisplatin (CDDP) against various solid tumors is often limited due to its poor selectivity and severe side effect. Considering this, in our study, CDDP was incorporated in fluorescent PEG amine grafted aldehyde hyaluronic acid by imine bond and metal ion coordination bond linking and formed a complex, the complex was then self-assembled into nanoparticles in water simply. FT-IR, XRD, DLS and SEM analysis demonstrated that the nanoparticles were prepared successfully and exhibited a spherical structure with size ranged from 216.4 to 372.3 nm in diameter. CDDP releasing from the nanoparticles was in a controlled manner, and had faster release rate at lower pH, indicating the nanoparticles were responsive to tumor micro-acid environment. Since fluorescent Cy5.5 and targeting hyaluronic acid existed on the surface of the nanoparticles, CLSM images clearly showed that the nanoparticles could target and internalize into HeLa cells, and then inhibited the growth of HeLa cells. In addition, MTT, AO-EB staining, and hemolysis assay showed that the nanoparticles had good cyto-/hemo-compatibility. Hence, the nanoparticles had the potential to be used for cancer therapy and diagnosis. The further in vivo experiment will be shown in the next work. pH responsible and fluorescent Cy5.5-PEG-g-A-HA/CDDP complex nanoparticles were facilely fabricated for controlled and targeted delivery of CDDP.

pH-Promoted Release of a Novel Anti-Tumour Peptide by "Stealth" Liposomes: Effect of Nanocarriers on the Drug Activity in Cis-Platinum Resistant Cancer Cells

PURPOSE

To evaluate the potential effects of PEGylated pH-sensitive liposomes on the intracellular activity of a new peptide recently characterized as a novel inhibitor of the human thymidylate synthase (hTS) over-expressed in many drug-resistant human cancer cell lines.

METHODS

Peptide-loaded pH-sensitive PEGylated (PpHL) and non-PEGylated liposomes (nPpHL) were carefully characterized and delivered to cis-platinum resistant ovarian cancer C13* cells; the influence of the PpHL on the drug intracellular activity was investigated by the Western Blot analysis of proteins involved in the pathway affected by hTS inhibition.

RESULTS

Although PpHL and nPpHL showed different sizes, surface hydrophilicities and serum stabilities, both carriers entrapped the drug efficiently and stably demonstrating a pH dependent release; moreover, the different behavior against J774 macrophage cells confirmed the ability of PEGylation in protecting liposomes from the reticuloendothelial system. Comparable effects were instead observed against C13* cells and biochemical data by immunoblot analysis indicated that PEGylated pH-sensitive liposomes do not modify the proteomic profile of the cells, fully preserving the activity of the biomolecule.

CONCLUSION

PpHL can be considered as efficient delivery systems for the new promising anti-cancer peptide.

Human Thymidylate Synthase Inhibitors Halting Ovarian Cancer Growth

Human thymidylate synthase (hTS) has an important role in DNA biosynthesis, thus it is essential for cell survival. TS is involved in the folate pathways, specifically in the de novo pyrimidine biosynthesis. Structure and functions are intimately correlated, account for cellular activity and, in a broader view, with in vivo mechanisms. hTS is a target for anticancer agents, some of which are clinical drugs. The understanding of the detailed mechanism of TS inhibition by currently used drugs and of the interaction with the mechanism of action of other anticancer agents can suggest new perspective of TS inhibition able to improve the anticancer effect and to overcome drug resistance. TS-targeting drugs in therapy today are inhibitors that bind at the active site and that mostly resemble the substrates. Nonsubstrate analogs offer an opportunity for allosteric binding and novel mode of inhibition in the cancer cells. This chapter illustrates the relationship among the large number of hTS actions at molecular and clinical levels, its role as a target for ovarian cancer therapy, in particular in cases of overexpression of hTS and other folate proteins such as those induced by platinum drug treatments, and address the potential combination of TS inhibitors with other suitable anticancer agents.

Crystal structures of nematode (parasitic T. spiralis and free living C. elegans), compared to mammalian, thymidylate synthases (TS). Molecular docking and molecular dynamics simulations in search for nematode-specific inhibitors of TS

Three crystal structures are presented of nematode thymidylate synthases (TS), including Caenorhabditis elegans (Ce) enzyme without ligands and its ternary complex with dUMP and Raltitrexed, and binary complex of Trichinella spiralis (Ts) enzyme with dUMP. In search of differences potentially relevant for the development of species-specific inhibitors of the nematode enzyme, a comparison was made of the present Ce and Ts enzyme structures, as well as binary complex of Ce enzyme with dUMP, with the corresponding mammalian (human, mouse and rat) enzyme crystal structures. To complement the comparison, tCONCOORD computations were performed to evaluate dynamic behaviors of mammalian and nematode TS structures. Finally, comparative molecular docking combined with molecular dynamics and free energy of binding calculations were carried out to search for ligands showing selective affinity to T. spiralis TS. Despite an overall strong similarity in structure and dynamics of nematode vs mammalian TSs, a pool of ligands demonstrating predictively a strong and selective binding to TsTS has been delimited. These compounds, the E63 family, locate in the dimerization interface of TsTS where they exert species-specific interactions with certain non-conserved residues, including hydrogen bonds with Thr174 and hydrophobic contacts with Phe192, Cys191 and Tyr152. The E63 family of ligands opens the possibility of future development of selective inhibitors of TsTS and effective agents against trichinellosis.

Nanocarrier fabrication and macromolecule drug delivery: challenges and opportunities

Macromolecules (proteins/peptides) have the potential for the development of new therapeutics. Due to their specific mechanism of action, macromolecules can be administered at relatively low doses compared with small-molecule drugs. Unfortunately, the therapeutic potential and clinical application of macromolecules is hampered by various obstacles including their large size, short in vivo half-life, phagocytic clearance, poor membrane permeability and structural instability. These challenges have encouraged researchers to develop novel strategies for effective delivery of macromolecules. In this review, various routes of macromolecule administration (invasive/noninvasive) are discussed. The advantages/limitations of novel delivery systems and the potential role of nanotechnology for the delivery of macromolecules are elaborated. In addition, fabrication approaches to make nanoformulations in different shapes and sizes are also summarized.

Preclinical safety of solid lipid nanoparticles and nanostructured lipid carriers: Current evidence from in vitro and in vivo evaluation

Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) were designed as exceptionally safe colloidal carriers for the delivery of poorly soluble drugs. SLN/NLC have the particularity of being composed of excipientsalready approved for use in medicines for human use, which offers a great advantage over any other nanoparticulate system developed from novel materials. Despite this fact, any use of excipients in new route of administration or in new dosage form requires evidence of safety. After 25 years of research on SLN and NLC, enough evidence on their preclinical safety has been published. In the present work, published data on in vitro and in vivo compatibility of SLN/NLC have been surveyed, in order to provide evidence of high biocompatibility distinguished by intended administration route. We also identified critical factors and possible weak points in SLN/NLC formulations, such as the effect of surfactants on the cell viability in vitro, which should be considered for further development.