Search

Organically modified clays can be used as nanofillers in polymer-clay nanocomposites to create bio-based packaging with improved strength and barrier properties. The impact of organic modification on the physico-chemical properties and toxicity of clays has yet to be fully investigated but is essential to ensure their safe use. Two organoclays, named N116_HDTA and N116_TMSA, were prepared using a commercially available sodium bentonite clay and the organic modifiers hexadecyl trimethyl ammonium bromide (HDTA) and octadecyl trimethyl ammonium chloride (TMSA). An in vitro hazard assessment was performed using HaCaT skin cells, C3A liver cells, and J774.1 macrophage-like cells. Organic modification with HDTA and TMSA increased the hazard potential of the organoclays in all cell models, as evidenced by the higher levels of cytotoxicity measured. N116_TMSA caused the greatest loss in viability with IC50 values of 3.2, 3.6 and 6.1 μg/cm2 calculated using J774.1, HaCaT and C3A cell lines, respectively. Cytotoxic effects were dictated by the amount of free or displaced organic modifier present in the exposure suspensions. The parent bentonite clay also caused distinct cytotoxic effects in J774.1 macrophage-like cells with associated TNF-α release. Such information on the hazard profile of organoclays, can feed into risk assessments for these materials.

Conjugation of recombinant human deoxyribonuclease I (rhDNase) to polyethylene glycol (PEG) of 20 to 40 kDa was previously shown to prolong the residence time of rhDNase in the lungs of mice after pulmonary delivery while preserving its full enzymatic activity. This work aimed to study the fate of native and PEGylated rhDNase in the lungs and to elucidate their biodistribution and elimination pathways after intratracheal instillation in mice. In vivo fluorescence imaging revealed that PEG30 kDa-conjugated rhDNase (PEG30-rhDNase) was retained in mouse lungs for a significantly longer period of time than native rhDNase (12 days vs 5 days). Confocal microscopy confirmed the presence of PEGylated rhDNase in lung airspaces for at least 7 days. In contrast, the unconjugated rhDNase was cleared from the lung lumina within 24 h and was only found in lung parenchyma and alveolar macrophages thereafter. Systemic absorption of intact rhDNase and PEG30-rhDNase was observed. However, this was significantly lower for the latter. Catabolism, primarily in the lungs and secondarily systemically followed by renal excretion of byproducts were the predominant elimination pathways for both native and PEGylated rhDNase. Catabolism was nevertheless more extensive for the native protein. On the other hand, mucociliary clearance appeared to play a less prominent role in the clearance of those proteins after pulmonary delivery. The prolonged presence of PEGylated rhDNase in lung airspaces appears ideal for its mucolytic action in patients with cystic fibrosis.