Effective density of inhaled environmental and engineered nanoparticles and its impact on the lung deposition and dosimetry.

BACKGROUND: Airborne environmental and engineered nanoparticles (NPs) are inhaled and deposited in the respiratory system. The inhaled dose of such NPs and their deposition location in the lung determines their impact on health. When calculating NP deposition using particle inhalation models, a common approach is to use the bulk material density, ρb, rather than the effective density, ρeff. This neglects though the porous agglomerate structure of NPs and may result in a significant error of their lung-deposited dose and location. RESULTS: Here, the deposition of various environmental NPs (aircraft and diesel black carbon, wood smoke) and engineered NPs (silica, zirconia) in the respiratory system of humans and mice is calculated using the Multiple-Path Particle Dosimetry model accounting for their realistic structure and effective density. This is done by measuring the NP ρeff which was found to be up to one order of magnitude smaller than ρb. Accounting for the realistic ρeff of NPs reduces their deposited mass in the pulmonary region of the respiratory system up to a factor of two in both human and mouse models. Neglecting the ρeff of NPs does not alter significantly the distribution of the deposited mass fractions in the human or mouse respiratory tract that are obtained by normalizing the mass deposited at the head, tracheobronchial and pulmonary regions by the total deposited mass. Finally, the total deposited mass fraction derived this way is in excellent agreement with those measured in human studies for diesel black carbon. CONCLUSIONS: The doses of inhaled NPs are overestimated by inhalation particle deposition models when the ρb is used instead of the real-world effective density which can vary significantly due to the porous agglomerate structure of NPs. So the use of realistic ρeff, which can be measured as described here, is essential to determine the lung deposition and dosimetry of inhaled NPs and their impact on public health.

Surface stabilization determines macrophage uptake, cytotoxicity, and bioactivity of curcumin nanocrystals.

Pharmaceutical nanocrystals represent a promising new formulation that combines the benefits of bulk crystalline materials and colloidal nanoparticles. To be applied in vivo, nanocrystals must meet several criteria, namely colloidal stability in physiological media, non-toxicity to healthy cells, avoidance of macrophage clearance, and bioactivity in the target tissue. In the present work, curcumin, a naturally occurring poorly water-soluble molecule with a broad spectrum of bioactivity has been considered a candidate substance for preparing pharmaceutical nanocrystals. Curcumin nanocrystals in the size range of 40-90 nm were prepared by wet milling using the following combination of steric and ionic stabilizers: Tween 80, sodium dodecyl sulfate, Poloxamer 188, hydroxypropyl methylcellulose, phospholipids (with and without polyethylene glycol), and their combination. Nanocrystals stabilized by a combination of phospholipids enriched with polyethylene glycol proved to be the most successful in all evaluated criteria; they were colloidally stable in all media, exhibited low macrophage clearance, and proved non-toxic to healthy cells. This curcumin nanoformulation also exhibited outstanding anticancer potential comparable to commercially used cytostatics (IC50 = 73 µM; 24 h, HT-29 colorectal carcinoma cell line) which represents an improvement of several orders of magnitude when compared to previously studied curcumin formulations. This work shows that the preparation of phospholipid-stabilized nanocrystals allows for the conversion of poorly soluble compounds into a highly effective "solution-like" drug delivery system at pharmaceutically relevant drug concentrations.

Antibody-pHPMA functionalised fluorescent silica nanoparticles for colorectal carcinoma targeting.

The systemic application of highly potent drugs such as cytostatics poses the risks of side effects, which could be reduced by using a carrier system able to specifically deliver the encapsulated drug to the target tissue. Essential components of a nanoparticle-based drug delivery system include the drug carrier itself, a targeting moiety, and a surface coating that minimizes recognition by the immune system. The present work reports on the preparation, in vitro characterization and in vivo testing of a new delivery system consisting of fluorescent silica nanoparticles functionalised with a non-immunogenic stealth polymer poly(N-(2-hydroxypropyl)methacrylamide) (pHPMA) and a monoclonal antibody IgG M75 that specifically binds to Carbonic Anhydrase IX (CA IX). CA IX is a promising therapeutic target, as it is a hallmark of several hypoxic tumours including colorectal carcinoma. Uniquely in this work, the monoclonal antibody was covalently coupled to the surface of fluorescently labelled silica nanoparticles via a multivalent amino-reactive co-polymer rather than a traditional bivalent linker. The pHPMA-M75 functionalised SiO2 nanoparticles exhibited excellent colloidal stability in physiological media. Their in vitro characterisation by flow cytometry proved a highly specific interaction with colorectal carcinoma cells HT-29. In vivo study on athymic NU/NU nude mice revealed that the SiO2-pHPMA-M75 nanoparticles are capable of circulating in the blood after intravenous administration and accumulate in the tumour at tenfold higher concentration than nanoparticles without specific targeting, with a considerably longer retention time. Additionally, it was found that by reducing the dose administered in vivo, the selectivity of the nanoparticle biodistribution could be further enhanced in favour of the tumour.