Novel Core-Shell Polyamine Phosphate Nanoparticles Self-Assembled from PEGylated Poly(allylamine hydrochloride) with Low Toxicity and Increased In Vivo Circulation Time

An approach for reducing toxicity and enhancing therapeutic potential of supramolecular polyamine phosphate nanoparticles (PANs) through PEGylation of polyamines before their assembly into nanoparticles is presented here. It is shown that the number of polyethylene glycol (PEG) chains for polyamine largely influence physico-chemical properties of PANs and their biological endpoints. Poly(allylamine hydrochloride) (PAH) are functionalized through carbodiimide chemistry with three ratios of PEG molecules per PAH chain: 0.1, 1, and 10. PEGylated PAH is then assembled into PANs by exposing the polymer to phosphate buffer solution. PANs decrease size and surface charge with increasing PEG ratios as evidenced by dynamic light scattering and zeta potential measurements, with the ten PEG/PAH ratio PANs having practically zero charge. Small angle X-ray scattering (SAXS) proves that PEG chains form a shell around a polyamine core, which is responsible for the screening of positive charges. MTT experiments show that the screening of amine groups decreases nanoparticle toxicity, with the lowest toxicity for the 10 PEG/PAH ratio. Fluorescence correlation spectroscopy (FCS) proves less interaction with proteins for PEGylated PANs. Positron emission tomography (PET) imaging of ¹⁸ F labelled PANs shows longer circulation time in healthy mice for PEGylated PANs than non-PEGylated ones.

In Vivo Tracking of the Degradation of Mesoporous Silica through 89 Zr Radio-Labeled Core-Shell Nanoparticles

While mesoporous silica nanoparticles (MSNs) are extensively studied as high-potential drug delivery platforms, the successful clinical translation of these nanocarriers strongly depends on their biodistribution, biodegradation, and elimination patterns in vivo. Here, a novel method is reported to follow the in vivo degradation of MSNs by tracking a radioactive label embedded in the silica structure. Core-shell silica nanoparticles (NPs) with a dense core and a mesoporous shell are labeled with low quantities of the positron emitter ⁸⁹ Zr, either in the dense core or in the mesoporous shell. In vivo positron emission tomography imaging and ex vivo organ measurements reveal a remarkable difference in the ⁸⁹ Zr biodistribution between the shell-labeled and the core-labeled NPs. Release of the radiotracer from shell-labeled NPs is used as a probe of the extent of silica dissolution, and a prompt release of the radioisotope is observed, with partial excretion already in the first 2 h post injection, and a slower accumulation in bones over time. On the other hand, when ⁸⁹ Zr is embedded in the nanoparticle core, the biodistribution remains largely unchanged during the first 6 h. These findings indicate that MSNs have fast, hour-scale, degradation kinetics in vivo.

Visible-Light Acceleration of H2 Evolution from Aqueous Solutions of Inorganic Hydrides Catalyzed by Gold-Transition-Metal Nanoalloys

Production of hydrogen (H₂) upon hydrolysis of inorganic hydrides potentially is a key step in green energy production. We find that visible-light irradiation of aqueous solutions of ammonia-borane (AB) or NaBH₄ containing "click"-dendrimer-stabilized alloyed nanocatalysts composed of nanogold and another late transition-metal nanoparticle (LTMNP) highly enhances catalytic activity for H₂ generation while also inducing alloy to Au core@M shell nanocatalyst restructuration. In terms of visible-light-induced acceleration of H₂ production from both AB and NaBH₄, the Au₁Ru₁ alloy catalysts show the most significant light-boosting effect. Au-Rh and Au-PtNPs are also remarkable with total H₂ release time from AB and NaBH₄ down to 1.3 min at 25 °C (AuRh), 3 times less than in the dark, and Co is the best earth-abundant metal alloyed with nanogold. This boosting effect is explained by the transfer of plasmon-induced hot electron from the Au atoms to the LTMNP atoms facilitating water O-H oxidative addition on the LTMNP surface, as shown by the large primary kinetic isotope effect k_H/k_D upon using D₂O obtained for both AB and NaBH₄. The second simultaneous and progressive effect of visible-light irradiation during these reactions, alloy to Au core@M shell restructuration, enhances the catalytic activity in the recycling, because, in the resulting Au core@M shell, the surface metal (such as Ru) is much more active than the original Au-containing alloy surface in dark reactions. There is no light effect on the rate of hydrogen production for the recycled nanocatalyst because of the absence of Au on the NP surface, but it is still very efficient in hydrogen release during four cycles because of the initial light-induced restructuration, although it is slightly less efficient than the original nanoalloy in the presence of light. The dendritic triazole coordination on each LTMNP surface appears to play a key role in these remarkable light-induced processes.

Poloxamer/sodium cholate co-formulation for micellar encapsulation of doxorubicin with high efficiency for intracellular delivery: An in-vitro bioavailability study

HYPOTHESIS

Doxorubicin hydrochloride (DX) is widely used as a chemotherapeutic agent, though its severe side-effects limit its clinical use. A way to overcome these limitations is to increase DX latency through encapsulation in suitable carriers. However, DX has a high solubility in water, hindering encapsulation. The formulation of DX with sodium cholate (NaC) will reduce aqueous solubility through charge neutralization and hydrophobic interactions thus facilitating DX encapsulation into poloxamer (F127) micelles, increasing drug latency.

EXPERIMENTS

DX/NaC/PEO-PPO-PEO triblock copolymer (F127) formulations with high DX content (DX-PMs) have been prepared and characterized by scattering techniques, transmission electron microscopy and fluorescence spectroscopy. Cell proliferation has been evaluated after DX-PMs uptake in three cell lines (A549, Hela, 4T1). Cell uptake of DX has been studied by means of confocal laser scanning microscopy and flow cytometry.

FINDINGS

DX-PMs formulations result in small and stable pluronic micelles, with the drug located in the apolar core of the polymeric micelles. Cell proliferation assays show a delayed cell toxicity for the encapsulated DX compared with the free drug. Data show a good correlation between cytotoxic response and slow DX delivery to nuclei. DX-PMs offer the means to restrict DX delivery to the cell interior in a highly stable and biocompatible formulation, suitable for cancer therapy.

Polyphosphate Poly(amine) Nanoparticles: Self-Assembly, Thermodynamics, and Stability Studies

The interaction of polyamine poly(allylamine hydrochloride) with Na₃PO₄, Na₄P₂O₇, Na₅P₃O₁₀, Na₆P₆O₁₈, and (NaPO₃)₂₆ salts and the formation of polyamine phosphate nanoparticles (PANs) are studied here. Dynamic light scattering, isothermal titration calorimetry (ITC), electrophoretical mobility measurements, atomic force microscopy, and transmission electron microscopy are used to explore the formation, stability, and pH sensitivity of PANs. An optimal concentration for PAN formation is found for each phosphate salt in terms of the most stable size and lowest polydispersity index of the nanoparticles. The minimal concentration of phosphate ions for PAN formation decreases with the increasing number of phosphate groups per phosphate salt. ITC measurements show that all polyphosphates display a characteristic endothermic peak, which is not present when monophosphates are used for PAN formation. pH stability of PANs depends on the type of phosphate salt. PANs formed with small phosphates show a small window of stability with pH from 8 to 9, while those formed with long phosphates are stable in more acidic pH environments. Our findings open multiple possibilities for fine-tuning the pH sensitivity of PANs by varying phosphate salts for potential applications in drug delivery.

Self-assembly of poly(allylamine)/siRNA nanoparticles, their intracellular fate and siRNA delivery

Silencing RNA (siRNA) technologies attract significant interest as a therapeutic tool for a large number of diseases. However, the medical translation of this technology is hampered by the lack of effective delivery vehicles for siRNAs in cytosol that prevent their degradation in the bloodstream. The use of molecular complexes based on polyamines have great potential for siRNA delivery as polyamines can protect the siRNA during circulation and at the same time favor siRNA translocation in cytosol. Here, nanoparticles are prepared by complexation of poly(allylamine hydrochloride) (PAH) and siRNA varying the ratio of nitrogen groups from PAH to phosphate groups from siRNA (N/P ratio). Nanoparticles are characterized by transmission electron microscopy and dynamic light scattering. The stability of complexes of green rhodamine labelled PAH (G-PAH) and Cy5 labelled siRNA (R-siRNA) at different pHs and in cell media is studied by fluorescence cross-correlation spectroscopy (FCCS). FCCS studies show that the nanoparticles are stable at physiological pH and in cell media but they disassemble at acidic pH. An optimal N/P ratio of 2 is identified in terms of stability in media, degradation at endosomal pH and toxicity. The intracellular fate of the complexes is studied following uptake in A549 cells. The cross-correlation between G-PAH and R-siRNA decreases substantially 24 h after uptake, while diffusion times of siRNA decrease indicating that the complexes disassemble, liberating the siRNAs. The release of siRNAs into the cytosol is confirmed with parallel confocal laser scanning microscopy. Flow cytometry studies show that PAH/siRNA nanoparticles are effective at silencing green fluorescent protein expression at low N/P ratios at which polyethylenimine/siRNA shows no significant silencing.