Noha M. Zaki

Gateways for the intracellular access of nanocarriers: a review of receptor-mediated endocytosis mechanisms and of strategies in receptor targeting.

Importance of the field: The last 10 years have seen a dramatic growth in understanding and controlling how complex, drug-loaded (nano)structures, as well as pathogens, or biopharmaceuticals can gather access to the cytoplasm, which is a key step to increasing the effectiveness of their action. Areas covered in this review: The review offers an updated overview of the current knowledge of endocytic processes; furthermore, the cell surface receptors most commonly used in drug delivery are here discussed on the basis of their reported internalization mechanisms, with examples of their use as nanocarrier targets taken from the most recent scientific literature. What the reader will gain: Knowledge of molecular biology details is increasingly necessary for a rational design of drug delivery systems. Here, the aim is to provide the reader with an attempt to link a mechanistic knowledge of endocytic mechanisms with the identification of appropriate targets (internalization receptors) for nanocarriers. Take home message: Much advance is still needed to create a complete and coherent biological picture of endocytosis, but current knowledge already allows individuation of a good number of targetable groups for a predetermined intracellular fate of nanocarriers.

Nanocarriers for cytoplasmic delivery: cellular uptake and intracellular fate of chitosan and hyaluronic acid-coated chitosan nanoparticles in a phagocytic cell model.

The cellular uptake of hyaluronic-acid-coated, negatively charged chitosan/triphosphate nanoparticles and that of uncoated, positively charged ones is investigated by studying cellular localization, uptake kinetics and mechanism of internalization in J774.2 macrophages, using non-phagocytic L929 fibroblasts as a control for uncoated nanoparticles. Both kinds of nanoparticles undergo endosomal escape and adopt a similar clathrin-based endocytic mechanism. The surface decoration with HA profoundly influences the kinetics of cellular uptake, with an at least two orders of magnitude slower kinetics, but also the nature of the binding on the cellular surface.

Bioavailability enhancement of verapamil HCl via intranasal chitosan microspheres

Chitosan microspheres are potential drug carriers for maximizing nasal residence time, circumventing rapid mucociliary clearance and enhancing nasal absorption. The aim of the present study was to develop and characterize chitosan mucoadhesive microspheres of verapamil hydrochloride (VRP) for intranasal delivery as an alternative to oral VRP which suffers low bioavailability (20%) due to extensive first pass effect. The microspheres were produced using a spray-drying and precipitation techniques and characterized for morphology (scanning electron microscopy), particle size (laser diffraction method), drug entrapment efficiency, thermal behavior (differential scanning calorimetry) and crystallinity (X-ray diffractometric studies) as well as in vitro drug release. Bioavailability of nasal VRP microspheres was studied in rabbits and the results were compared to those obtained after nasal, oral and intravenous administration of VRP solution. Results demonstrated that the microspheres were spherical with size 21-53 μm suitable for nasal deposition. The spray-drying technique was superior over precipitation technique in providing higher VRP entrapment efficiency and smaller burst release followed by a more sustained one over 6h. The bioavailability study demonstrated that the nasal microspheres exhibited a significantly higher bioavailability (58.6%) than nasal solution of VRP (47.8%) and oral VRP solution (13%). In conclusion, the chitosan-based nasal VRP microspheres are promising for enhancing VRP bioavailability by increasing the nasal residence time and avoiding the first-pass metabolism of the drug substance.

PEGylation of nanosubstrates (Titania) with multifunctional reagents: At the crossroads between nanoparticles and nanocomposites

Titania (anatase) nanoparticles were successfully PEGylated through the use of catechol (dopamine)-terminated PEG derivatives. The resulting materials were characterized by excellent stability at neutral pH and extremely low toxicity (phagocytic and nonphagocytic cell lines). In particular, we focused on the comparison between mono- and bis-catechol PEGs. Due to the double terminal anchorage on the titania surface, bis-catechol ligands can produce chains differing from classical monoanchored PEG in conformation (horseshoe-shaped vs brush) and thus the possibility of interactions with biomolecules. At the same time, less than quantitative catechol binding may lead to the presence of dangling chains with unbound catechols which can polymerize and eventually produce PEG/titania nanocomposite colloids. Our results on double-functional PEG2000 show the latter to be the case. Pluronic F127 was also used as a bifunctional ligand, leading to nanocomposite aggregates with an even larger organic content.

A comparative study of chitosan shielding effect on nano-carriers hydrophilicity and biodistribution

Engineering polymer surfaces reduces nanoparticles (NPs) aggregation and phagocytosis due to effective shielding, hindering recognition by the reticuloendothelial system (RES). The shielding of NPs is complex and affected by the type of groups used in terms of charge and hydrophilicity. This will, in turn, affect NPs biodistribution which will determine the length of activity of the drug. Polysaccharides are nowadays recognized for decreasing the uptake of particulate carriers by the mononuclear phagocytic system (MPS). Chitosan is considered as an attractive candidate due to its biocompatibility, biodegradability, non-toxicity and low cost. In this study clozapine (CZP)-loaded NPs were coated with chitosan, pluronic F-68, polyethylene glycol (PEG) 4000 and polysorbate 80. The factors affecting drug encapsulation efficiency, particle size, surface charge, surface hydrophilicity, pharmacokinetics and biodistribution were studied. The results proved that although a similarity in surface hydrophilicity, chitosan-stealth NPs showed different pharmacokinetic profile and biodistribution behavior compared to polysorbate-stealth NPs.

Augmented cytotoxicity of hydroxycamptothecin-loaded nanoparticles in lung and colon cancer cells by chemosensitizing pharmaceutical excipients.

Abstract The aim of this was to investigate and compare the chemosensitizing effect of some pharmaceutical excipients (TPGS, Pluronic P85 and chitosan) by evaluating the cytotoxicity of the chemotherapeutic drug Hydroxy Camptothecin (HCPT) loaded into PLGA nanoparticles. Different nanoparticles formulations were developed and evaluated for size, zeta potential, morphology, loading and encapsulation efficiency as well as in vitro drug release. The cytotoxicity of the nanoparticles was evaluated by MTT assay in A549 (human lung carcinoma cell line) and HT29 (human colon carcinoma cell line) whereas their cellular uptake was determined by confocal laser scanning microscopy and microfluorimetry assay. The results revealed that nanoparticles possessed a desirable nanometric size (revealed by dynamic light scattering measurements and TEM) with appreciable HCPT encapsulation (>48%) and negative surface charge that was switched to positive upon coating with chitosan. The nanoparticles adopted a sustained release phase preceded by initial burst of HCPT that was reduced by chitosan coating. The cytotoxicity of the nanoparticles in A549 and HT29 cells was significantly augmented compared to simple drug solution and basic nanoparticles without excipients. The excipients could be ranked according to their IC50 lowering effect in the following order [TPGS (sixfold lower IC50) > Pluronic P85 > Chitosan]. The augmented cytotoxicity and chemosensitizing effect might be attributed to overcoming drug efflux (in case of TPGS 1000 or Pluronic P85) and/or maximizing internalization by cancer cells (chitosan coating). Acting as chemopotentiators, the studied excipients could have potential in reducing therapeutic HCPT doses and minimizing adverse effects in lung and colon chemotherapy.

Assessment of nanomaterials cytotoxicity and internalization.

The impact that nanotechnology may have on life and medical sciences is immense and includes novel therapies as much as novel diagnostic and imaging tools, often offering the possibility to combine the two. It is, therefore, of the essence to understand and control the interactions that nanomaterials can have with cells, first at an individual level, focusing on, e.g., binding and internalization events, and then at a tissue level, where diffusion and long-range transport add further complications. Here, we present experimental methods based on selective labeling techniques and the use of effectors for a qualitative and quantitative evaluation of endocytic phenomena involving nanoparticles. The understanding of the cell-material interactions arising from these tests can then form the basis for a model-based evaluation of nanoparticles behavior in 3D tissues.

Impact of microparticle formulation approaches on drug burst release: a level A IVIVC

Abstract Aim: To study the effect of poly(d,l-lactic-co-glycolic acid) (PLGA) microparticles (MPs) preparation techniques on particle physical characterization with special emphasis on burst drug release. Methods: A basic drug clozapine was used in combination with acid-terminated PLGA. Two approaches for MP preparation were compared; the in situ forming microparticle (ISM) and the emulsion-solvent evaporation (ESE) methods using an experimental design. The MPs obtained were compared according to their physical characterization, burst release and T80%. An in vivo pharmacokinetic study with in vitro–in vivo correlation (IVIVC) was also performed for the selected formula. Results: Both methods were able to sustain drug release for three weeks. ISM produced more porous particles and was not effective as ESE for controlling burst release. A good IVIVC (R2 = 0.9755) was attained when injecting the selected formula into rats. Conclusion: MPs prepared with ESE showed a minimum burst release and a level A IVIVC was obtained when administered to rats.