Physisorption of Poly(ethylene glycol) on Inorganic Nanoparticles

Triple-transformable dynamic surroundings for programmed transportation of bio-vulnerable mRNA payloads towards systemic treatment of intractable solid tumors

The surface physiochemical properties of nanomedicine play a crucial role in modulating biointerfacial reactions in sequential biological compartments, accordingly accomplishing the desired programmed delivery scenario to intracellular targets. PEGylation, which involves modifying the surface with a layer of poly(ethylene glycol), has been validated as an effective strategy for minimizing adverse biointerfacial interactions. However, it has also been observed to impede cellular uptake and intracellular trafficking activities. To address this dilemma, we propose a dynamic surface chemistry approach that actively prevents non-specific reactions in systemic circulation, while readily facilitating cellular uptake by converting into a highly cytomembrane-adhesive state. Moreover, the surface becomes more adhesive to endolysosomal membranes, enabling translocation into the cytosol. In this study, PEGylated mRNA delivery nanoparticulates were tethered with charge-reversible polymers to create dynamic surroundings through click chemistry. Importantly, the dynamic surroundings exhibited negative charges under physiological conditions (pH 7.4). This property prevented degradation by anionic nucleases and structural disassembly induced by endogenous charged biological species. Consequently, the nanoparticles exhibited appreciable stealth function, effectively managing the first pass effect, leading to prolonged blood retention and improved bioavailabilities at targeted cells. Furthermore, the dynamic surroundings shifted towards relatively positive charges in the tumor microenvironment (pH 6.8). As a result, the nanoparticles were more likely to be taken up by tumors due to their electrostatic affinities towards polyanionic cytomembranes. Eventually, the internalized mRNA nanomedicine transformed responsive to the surrounding microenvironment into highly positive charges within acidic endolysosomes (pH 5.0), exerting explosive disruptive potencies on the endolysosomal structures, thus facilitating translocation of mRNA from the digestive endolysosomes into the targeted cytosol. Notably, the dynamic surroundings also reduced the immunogenicity of naked mRNA due to their stealthy properties and rapid endolysosomal translocation functions. In summary, our proposed unique triple-transformable dynamic surface chemistry provided an intriguing delivery scenario that overcomes sequential biological barriers, contributing to efficient expression of the encapsulated mRNA at targeted tumors.

Vacancy-engineered Mn-doped iron oxide nano-crystals for enhanced sonodynamic therapy through self-supplied oxygen

Sonodynamic therapy (SDT) is a minimally invasive therapeutic approach, that uses ultrasound activating sonosensitizers to generate reactive oxygen species (ROS) for inducing the tumor cell death. However, the SDT is always limited by the dissatisfactory performance of sonosensitizers and hypoxic tumor microenvironment (TME). Nano iron oxide is a narrow bandgap semiconductor material with good biocompatibility. The doping of manganese into iron oxide (Mn-doped iron oxide nano-crystals named Mn-Fe2O3 NCs) not only reduced the band gap of iron oxide and altered the valence band position of iron oxide, but also introduced more oxygen vacancies and inhibited the complexation of electrons (e-) and holes (h+), significantly enhancing the ability to generate ROS. The Mn-Fe2O3 NCs improved the hypoxic TME by self-generating oxygen and consuming endogenous glutathione (GSH), which amplified oxidative stress and further enhanced the SDT. The therapeutic results showed that the prepared Mn-Fe2O3 NCs could efficiently inhibit the triple-negative breast cancer (TNBC) cells by SDT (80.49 % inhibition ratio in vivo). Overall, we propose a simple method to design inorganic sonosensitizers for enhancing efficient sonodynamic therapy.

Oriented Linear Self-Assembly of Colloidal Nanocrystals through Regioselective Formation of Hydrogen-Bonded Supramolecular Bridges

The linear assembly of nanocrystals (NCs) with orientational order presents a significant challenge in the field of colloidal assembly. This study presents an efficient strategy for assembling oleic acid (OAH)-capped, faceted rare earth NCs─such as nanorods, nanoplates, and nanodumbbells─into flexible chain-like superstructures. Remarkably, these NC chains exhibit a high degree of particle orientation even with an interparticle distance reaching up to 15 nm. Central to this oriented assembly method is the facet-selective adsorption of low-molecular-weight polyethylene glycol (PEG), such as PEG-400 (Mn = 400), onto specific facets of NCs. This regioselectivity is achieved by exploiting the lower binding affinity of OAH ligands on the (100) facets of rare earth NCs, enabling facet-specific ligand displacement and subsequent PEG attachment. By adjusting the solvent polarity, the linear assembly of NCs is induced by the solvophobic effect, which simultaneously promotes the formation of hydrogen-bonded PEG supramolecular bridges. These supramolecular bridges effectively connect NCs and exhibit sufficient robustness to maintain the structural integrity of the chains, despite the large interparticle spacing. Notably, even when coassembling different types of NCs, the resulting multicomponent chains still feature highly selective facet-to-facet connections. This work not only introduces a versatile method for fabricating well-aligned linear superstructures but also provides valuable insights into the fundamental principles governing the facet-selective assembly of NCs in solution.

Enhanced split-type photoelectrochemical aptasensor incorporating a robust antifouling coating derived from four-armed polyethylene glycol

Antifouling biosensors capable of preventing protein nonspecific adhesion in real human bodily fluids are highly sought-after for precise disease diagnosis and treatment. In this context, an enhanced split-type photoelectrochemical (PEC) aptasensor was developed incorporating a four-armed polyethylene glycol (4A-PEG) to construct a robust antifouling coating, enabling accurate and sensitive bioanalysis. The split-type PEC system involved the photoelectrode and the biocathode, effectively separating signal converter with biorecogniton events. Specifically, the TiO2 electrode underwent sequential modification with ZnIn2S4 (ZIS) and polydopamine (PDA) to form the PDA/ZIS/TiO2 photoelectrode. The cathode substrate was synthesized as a hybrid of N-doped graphene loaded with Pt nanoparticles (NG-Pt), and subsequently modified with 4A-PEG to establish a robust antifouling coating. Following the anchoring of probe DNA (pDNA) on the 4A-PEG-grafted antifouling coating, the biocathode for model target of cancer antigen 125 (CA125) was obtained. Leveraging pronounced photocurrent output of the photoelectrode and commendable antifouling characteristics of the biocathode, the split-type PEC aptasensor showcased exceptional detection performances with high sensitivity, good selectivity, antifouling ability, and potential feasibility.

Surface Engineering and Programmed Self-Assembly of Silica Nanoparticles with Controllable Polystyrene/Poly(4-vinybenzyl azide) Patches

The programmed self-assembly of patchy nanoparticles (NPs) through a bottom-up approach is an efficient strategy for producing highly organized materials with a predetermined architecture. Herein, we report the preparation of di- and trivalent silica NPs with polystyrene (PS)/poly(4-vinylbenzyl azide) (PVBA) patches and assemble them in a THF mixture by lowering the solvent quality. Silica-PS/PVBA colloidal hybrid clusters were synthesized through the seeded growth emulsion copolymerization of styrene and 4-vinylbenzyl azide (VBA) in varying ratios. Subsequently, macromolecules on silica NPs originating from the copolymerization of growing PS or PVBA chains with the surface-grafted MMS compatibilizer are engineered by fine-tuning of polymer compositions or adjustment of solvent qualities. Moreover, multistage silica regrowth of tripod and tetrapod allowed a fine control of the patch-to-particle size ratio ranging from 0.69 to 1.54. Intriguingly, patchy silica NPs (1-, 2-, 3-PSNs) rather than hybrid clusters are successfully used as templates for multistep regrowth experiments, leading to the formation of silica NPs with a new morphology and size controllable PVBA/PS patches. Last but not least, combined with mesoscale dynamics simulations, the self-assembly kinetics of 2-PSN and 3-PSN into linear colloidal polymers and honeycomb-like lattices are studied. This work paves a new avenue for constructing colloidal polymers with a well-defined sequence and colloidal crystals with a predetermined architecture.

Homogeneous regulation of arranged polymorphic manganese dioxide nanocrystals as cathode materials for high-performance zinc-ion batteries

Rechargeable aqueous zinc-ion batteries have emerged as attractive energy storage devices by virtue of their low cost, high safety and eco-friendliness. However, zinc-ion cathodes are bottlenecked by their vulnerable crystal structures in the process of zinc embedding and significant capacity fading during long-term cycling. Herein, we report the rational and homogeneous regulation of polycrystalline manganese dioxide (MnO₂) nanocrystals as zinc cathodes via a surfactant template-assisted strategy. Benefiting from the homogeneous regulation, MnO₂ nanocrystals with an ordered crystal arrangement, including nanorod-like polyvinylpyrrolidone-manganese dioxide (PVP-MnO₂), nanowire-like sodium dodecyl benzene sulfonate-manganese dioxide and nanodot-like cetyltrimethylammonium bromide-manganese dioxide, are obtained. Among these, the nanorod-like PVP-MnO₂ nanocrystals exhibit stable long-life cycling of 210 mAh g^-1 over 180 cycles at a high rate of 0.3 A g^-1 and with a high capacity retention of 84% over 850 cycles at a high rate of 1 A g^-1. The good performance of this cathode significantly results from the facile charge and mass transfer at the interface between the electrode and electrolyte, featuring the crystal stability and uniform morphology of the arranged MnO₂ nanocrystals. This work provides crucial insights into the development of advanced MnO₂ cathodes for low-cost and high-performance rechargeable aqueous zinc-ion batteries.

Biosafety risk assessment of gold and aluminum nanoparticles in tumor-bearing mice

To improve the biosafety of the nanodelivery system, this study developed novel monodisperse spherical aluminum nanoparticles (Al NPs) and evaluated their cytotoxicity in vitro and distribution and biotoxicity in vivo. Compared with gold nanoparticles of the same size, Al NPs not only had low cytotoxicity in vitro but also did not cause accumulation in major organs in vivo after intravenous injections. No significant abnormalities were observed in the serum biochemical indices of mice injected with Al NPs. Additionally, no substantial changes occurred in the histopathology of major organs, and no apparent biological toxicity was measured after consecutive injections of Al NPs. These results indicate that Al NPs have a good biological safety and provide a new method for developing low-toxicity nanomedicine.

Low-Fouling Gold Nanorod Theranostic Agents Enabled by a Sulfoxide Polymer Coating

Gold nanorods (GNRs) are widely used in various biomedical applications such as disease imaging and therapy due to their unique plasmonic properties. To improve their bioavailability, GNRs often need to be coated with hydrophilic polymers so as to impart stealth properties. Poly(ethylene glycol) (PEG) has been long used as such a coating material for GNRs. However, there is increasing acknowledgement that the amphiphilic nature of PEG facilitates its interaction with protein molecules, leading to immune recognition and consequent side effects. This has motivated the search for new classes of low-fouling polymers with high hydrophilicity as alternative low-fouling surface coating materials for GNRs. Herein, we report the synthesis, characterization, and application of GNRs coated with highly hydrophilic sulfoxide-containing polymers. We investigated the effect of the sulfoxide polymer coating on the cellular uptake and in vivo circulation time of the GNRs and compared these properties with pegylated GNR counterparts. The photothermal effect and photoacoustic imaging of these polymer-coated GNRs were also explored, and the results show that these GNRs are promising as nanotheranostic particles for the treatment of cancer.