Hagar I. Labouta

Tailor-made biofunctionalized nanoparticles using layer-by-layer technology.

Layer-by-layer (LBL) technique is a well-established method for the formation of nanofilms on planar surfaces, as well as on micro-sized colloidal particles. For surface functionalization of nanoparticles, it is a very recent area of research receiving great interest due to the advantage of obtaining fine control over the shell composition, charge and thickness, offering several applications in pharmaceutical and biomedical fields. This article provides an overview of the recent achievements in application of this technology on nanoparticles and their potential applications. Future research directions are also discussed.

Could Chemical Enhancement of Gold Nanoparticle Penetration Be Extrapolated from Established Approaches for Drug Permeation

Background and Aim: Investigations on chemical enhancement of skin penetration of gold nanoparticles are considered crucial to have a deeper insight into the main barrier of particle penetration. Methods: In this study, penetration of gold nanoparticles in the presence of several chemical enhancers – urea, sodium lauryl sulphate, polysorbate 80 and dimethyl sulfoxide (DMSO) – through human skin was studied. Results: Among the tested chemical enhancers, DMSO could induce the penetration of hydrophilic (citrate-stabilized) gold colloid of no intrinsic penetration ability in a concentration-dependent manner. Pretreatment of the skin with DMSO however reduced the penetration of hydrophobic (cetrimide-coated) gold nanoparticles as a result of aggregation in the top layers of the stratum corneum limiting penetration into the deeper skin layers. In addition, nanoparticles-vehicle interaction and the stability of the nanoparticles in the applied vehicle were found important determinants of skin penetration. Conclusion: Our results demonstrate that the already established approaches for chemical permeation enhancement of drug molecules and their postulated mechanisms could be used as preliminary guidelines for enhancing the penetration of nanoparticles. At this size range of 15 nm, intercellular lipids provide the main barrier to particle penetration through the stratum corneum.

Transdermal iontophoresis of flufenamic acid loaded PLGA nanoparticles

The objective of this study was to test in vitro a drug delivery system that combines nanoencapsulation and iontophoresis for the transdermal delivery of lipophilic model drug using poly(lactic-co-glycolic acid) (PLGA) as the carrier polymer. Negatively charged fluorescent nanoparticles loaded with negatively charged flufenamic acid were prepared. The colloidal properties of the particles were stable under iontophoretic current (constant, pulsed and alternating) profiles and in contact with skin barrier. The release of the drug from the particles was not affected by iontophoresis and remained always limited (≈50%), leading to significantly lower transdermal fluxes across human epidermis and full thickness porcine skin compared to respective free drug formulation. From nanoparticles, pulsed current profile resulted in comparable or higher fluxes compared to constant current profile although fluorescence imaging was not able to confirm deeper distribution of nanoparticles in skin. Based on our results, there is no clear advantage with respect to drug permeation from nanoencapsulating flufenamic acid into PLGA nanoparticles compared to free drug formulation, either in passive or iontophoretic delivery regimens. However, pulsed current iontophoresis could be an effective alternative instead of traditional constant current iontophoresis to enhance transdermal permeation of drugs from nanoencapsulated formulations.

Multivariate modeling of encapsulation and release of an ionizable drug from polymer microspheres

In the formulation of polymer microspheres (MSs) loaded with verapamil hydrochloride (VRP), a low molecular weight ionizable drug, by W/O/W emulsification, the pH of the external aqueous phase proved to be a primary determinant of both IE and drug release behavior. Increasing the pH of the external aqueous phase enhanced IE (approximately 100% at pH 8.4). This was associated with a considerable increase in initial release rate at pH 1.2. Two multivariate methods, factorial analysis (FA) and artificial neural network (ANN), were used to investigate the impact of the combined effect of the external phase pH and other parameters (polymer concentration and initial drug load) on MS characteristics; IE, initial drug release, MS size and yield. FA indicated that the external aqueous phase pH affected all responses, with a particularly strong correlation with IE in addition to a combined synergistic effect with polymer concentration on MS size. ANN showed better internal and external predictive ability of responses compared to FA. The ANN model developed in the study can be successfully used for multivariate modeling of the encapsulation and release of VRP and similar drug salts from hydrophobic polymer MSs prepared by multiple emulsification in addition to other MS characteristics.

Bacteriomimetic invasin-functionalized nanocarriers for intracellular delivery

Intracellular bacteria invade mammalian cells to establish an infectious niche. The current work models adhesion and subsequent internalization strategy of pathogenic bacteria into mammalian cells to design a bacteriomimetic bioinvasive delivery system. We report on the surface functionalization of liposomes with a C-terminal fragment of invasin (InvA497), an invasion factor in the outer membrane of Yersinia pseudotuberculosis. InvA497-functionalized liposomes adhere to mammalian epithelial HEp-2 cell line at different infection stages with a significantly higher efficiency than liposomes functionalized with bovine serum albumin. Covalent attachment of InvA497 results in higher cellular adhesion than liposomes with physically adsorbed InvA497 with non-specific surface protein alignment. Uptake studies in HEp-2 cells indicate active internalization of InvA497-functionalized liposomes via β1-integrin receptor-mediated uptake mechanism mimicking the natural invasion strategy of Y. pseudotuberculosis. Uptake studies in Caco-2 cells at different polarization states demonstrate specific targeting of the InvA497-functionalized liposomes to less polarized cells reflecting the status of inflamed cells. Moreover, when loaded with the anti-infective agent gentamicin and applied to HEp-2 cells infected with Y. pseudotuberculosis, InvA497-functionalized liposomes are able to significantly reduce the infection load relative to non-functionalized drug-loaded liposomes. This indicates a promising application of such a bacteriomimetic system for drug delivery to intracellular compartments.

Setup for investigating gold nanoparticle penetration through reconstructed skin and comparison to published human skin data

Abstract. Owing to the limited source of human skin (HS) and the ethical restrictions of using animals in experiments, in vitro skin equivalents are a possible alternative for conducting particle penetration experiments. The conditions for conducting penetration experiments with model particles, 15-nm gold nanoparticles (AuNP), through nonsealed skin equivalents are described for the first time. These conditions include experimental setup, sterility conditions, effective applied dose determination, skin sectioning, and skin integrity check. Penetration at different exposure times (two and 24 h) and after tissue fixation (fixed versus unfixed skin) are examined to establish a benchmark in comparison to HS in an attempt to get similar results to HS experiments presented earlier. Multiphoton microscopy is used to detect gold luminescence in skin sections. λex=800  nm is used for excitation of AuNP and skin samples, allowing us to determine a relative index for particle penetration. Despite the observed overpredictability of penetration into skin equivalents, they could serve as a first fast screen for testing the behavior of nanoparticles and extrapolate their penetration behavior into HS. Further investigations are required to test a wide range of particles of different physicochemical properties to validate the skin equivalent-human skin particle penetration relationship.

Polymethacrylate Microparticles Gel for Topical Drug Delivery

ABSTRACTPurposeEvaluating the potentials of particulate delivery systems in topical drug delivery.MethodsPolymethacrylate microparticles (MPs) incorporating verapamil hydrochloride (VRP) as a model hydrophilic drug with potential topical clinical uses, using Eudragit RS100 and Eudragit L100 were prepared for the formulation of a composite topical gel. The effect of initial drug loading, polymer composition, particularly the proportion of Eudragit L100 as an interacting polymer component and the HLB of the dispersing agent on MPs characteristics was investigated. A test MPs formulation was incorporated in gel and evaluated for drug release and human skin permeation.ResultsMPs showed high % incorporation efficiency and % yield. Composition of the hybrid polymer matrix was a main determinant of MPs characteristics, particularly drug release. Factors known to influence drug release such as MPs size and high drug solubility were outweighed by strong VRP-Eudragit L100 interaction. The developed MPs gel showed controlled VRP release and reduced skin retention compared to a free drug gel.ConclusionTopical drug delivery and skin retention could be modulated using particulate delivery systems. From a practical standpoint, the VRP gel developed may offer advantage in a range of dermatological conditions, in response to the growing off-label topical use of VRP.

Laser Scanning Microscopy Approach for Semiquantitation of In Vitro Dermal Particle Penetration

Skin penetration of nanoparticles is a recent research area in focus for the aim of development of topical nanoparticulate delivery systems as well as for health risk analysis. So far, monitoring skin penetration of nanoparticles is mostly based on qualitative microscopical examination. Here, we describe an experimental approach for extracting semiquantitative data from multiphoton images of skin specimens treated with gold nanoparticles. This will aid in depicting the factors responsible for enhancing or limiting nanoparticle penetration through the skin barrier.

Surface-grafted polyethylene glycol conformation impacts the transport of PEG-functionalized liposomes through a tumour extracellular matrix model

The effect of surface PEGylation on nanoparticle transport through an extracellular matrix (ECM) is an important determinant for tumor targeting success. Fluorescent stealth liposomes (base lipid DOPC) were prepared incorporating different proportions of PEG-grafted lipids (2.5, 5 and 10% of the total lipid content) for a series of PEG molecular weights (1000, 2000 and 5000 Da). The ECM was modelled using a collagen matrix. The kinetics of PEGylated liposome adhesion to and transport in collagen matrices were tracked using fluorescence correlation spectroscopy (FCS) and confocal microscopy, respectively. Generalized least square regressions were used to determine the temporal correlations between PEG molecular weight, surface density and conformation, and the liposome transport in a collagen hydrogel over 15 hours. PEG conformation determined the interaction of liposomes with the collagen hydrogel and their transport behaviour. Interestingly, liposomes with mushroom PEG conformation accumulated on the interface of the collagen hydrogel, creating a dense liposomal front with short diffusion distances into the hydrogels. On the other hand, liposomes with dense brush PEG conformation interacted to a lesser extent with the collagen hydrogel and diffused to longer distances. In conclusion, a better understanding of PEG surface coating as a modifier of transport in a model ECM matrix has resulted. This knowledge will improve design of future liposomal drug carrier systems.

Calcifediol-loaded liposomes for local treatment of pulmonary bacterial infections

Graphical abstract Figure. No caption available. ABSTRACT The influence of vitamin D3 and its metabolites calcifediol (25(OH)D) and calcitriol on immune regulation and inflammation is well described, and raises the question of potential benefit against bacterial infections. In the current study, 25(OH)D was encapsulated in liposomes to enable aerosolisation, and tested for the ability to prevent pulmonary infection by Pseudomonas aeruginosa. Prepared 25(OH)D‐loaded liposomes were nanosized and monodisperse, with a negative surface charge and a 25(OH)D entrapment efficiency of approximately 23%. Jet nebulisation of liposomes was seen to yield an aerosol suitable for tracheo‐bronchial deposition. Interestingly, 25(OH)D in either liposomes or ethanolic solution had no effect on the release of the proinflammatory cytokine KC from Pseudomonas‐infected murine epithelial cells (LA‐4); treatment of infected, human bronchial 16‐HBE cells with 25(OH)D liposomes however resulted in a significant reduction in bacterial survival. Together with the importance of selecting an application‐appropriate in vitro model, the current study illustrates the feasibility and practicality of employing liposomes as a means to achieve 25(OH)D lung deposition. 25(OH)D‐loaded liposomes further demonstrated promising effects regarding prevention of Pseudomonas infection in human bronchial epithelial cells.