Multifunctional stimuli-responsive hybrid nanogels for cancer therapy: Current status and challenges

With cancer research shifting focus to achieving multifunctionality in cancer treatment strategies, hybrid nanogels are making a rapid rise to the spotlight as novel, multifunctional, stimuli-responsive, and biocompatible cancer therapeutic strategies. They can possess cancer cell-specific cytotoxic effects themselves, carry drugs or enzymes that can produce cytotoxic effects, improve imaging modalities, and target tumor cells over normal cells. Hybrid nanogels bring together a wide range of desirable properties for cancer treatment such as stimuli-responsiveness, efficient loading and protection of molecules such as drugs or enzymes, and effective crossing of cellular barriers among other properties. Despite their promising abilities, hybrid nanogels are still far from being used in the clinic, and their available data remains relatively limited. However, many studies can be done to facilitate this clinical transition. This review is critically summarizing and analyzing the recent information and progress on the use of hybrid nanogels particularly inorganic nanoparticle-based and organic nanoparticle-based hybrid nanogels in the field of oncology and future directions to aid in transferring those results to the clinic. This work concludes that the future of hybrid nanogels is greatly impacted by therapeutic and non-therapeutic factors. Therapeutic factors include the lack of hemocompatibility studies, acute and chronic toxicological studies, and information on agglomeration capability and extent, tumor heterogeneity, interaction with proteins in physiological fluids, endocytosis-exocytosis, and toxicity of the nanogels' breakdown products. Non-therapeutic factors include the lack of clear regulatory guidelines and standardized assays, limitations of animal models, and difficulties associated with good manufacture practices (GMP).

Compact Peptoid Molecular Brushes for Nanoparticle Stabilization

Controlling the interfaces and interactions of colloidal nanoparticles (NPs) via tethered molecular moieties is crucial for NP applications in engineered nanomaterials, optics, catalysis, and nanomedicine. Despite a broad range of molecular types explored, there is a need for a flexible approach to rationally vary the chemistry and structure of these interfacial molecules for controlling NP stability in diverse environments, while maintaining a small size of the NP molecular shell. Here, we demonstrate that low-molecular-weight, bifunctional comb-shaped, and sequence-defined peptoids can effectively stabilize gold NPs (AuNPs). The generality of this robust functionalization strategy was also demonstrated by coating of silver, platinum, and iron oxide NPs with designed peptoids. Each peptoid (PE) is designed with varied arrangements of a multivalent AuNP-binding domain and a solvation domain consisting of oligo-ethylene glycol (EG) branches. Among designs, a peptoid (PE5) with a diblock structure is demonstrated to provide a superior nanocolloidal stability in diverse aqueous solutions while forming a compact shell (∼1.5 nm) on the AuNP surface. We demonstrate by experiments and molecular dynamics simulations that PE5-coated AuNPs (PE5/AuNPs) are stable in select organic solvents owing to the strong PE5 (amine)-Au binding and solubility of the oligo-EG motifs. At the vapor-aqueous interface, we show that PE5/AuNPs remain stable and can self-assemble into ordered 2D lattices. The NP films exhibit strong near-field plasmonic coupling when transferred to solid substrates.

Adsorption of Oligomeric Peroxides on Aerosil and Magnesium Oxide and Their Behavior on the Water-Air Phases Interface

Oligomeric peroxide adsorption of sebacic acid on aerosil and magnesium oxide was studied. Adsorption process parameters were found. It is shown that the adsorption takes place through the hydrogen bonds formation between OH– groups of adsorbents surface and peroxide groups. The adsorption process suggests the behavior of peroxide compounds on the water-air phase’s interface. Monomolecular film formations on water surface for oligomeric peroxides were studied. It was found that calculated values of the area extrapolated to zero pressure (S0) depend on the solvent which was used to apply the peroxide in the phases interface. Oligomeric peroxide monolayers considered as condensation-type monolayers. Thermal decomposition of oligomeric peroxide and its di- and monoperoxide analogues was studied. It was shown that total constants of thermal degradation rate k for oligomeric peroxide are higher than those for di- and monoperoxide analogues. There is a correlation between S0 calculated values and the constants of thermal degradation rate for oligoperoxide. The less is S0 value the higher is k value. The conformational state of the macromolecule was preserved during transferring the oligomeric peroxide solution in an organic solvent to the phases interface that affects k values.

Efficient Copper Removal from an Aqueous Anvironment using a Novel and Hybrid Nanoadsorbent Based on Derived-Polyethyleneimine Linked to Silica Magnetic Nanocomposites

Due to the extreme rise of sludge pollution with heavy metals (e.g. copper), the options for its disposal or treatment are decreasing. On the contrary, properly heavy metal-cleaned sludge can be used as an alternative sustainable energy and agriculture source. The aim of this study was to develop a novel nanoadsorbent, based on irreversibly linked amino-rich polymer onto previously silica-coated magnetic nanoparticles (MNPs) that can be applied efficiently for metal removal. MNPs were coated uniformly by 3 nm thick silica layer (core-shell structure), and were additionally modified with systematic covalent attachment of derived branched polyethyleneimine (bPEI). The formed structure of synthesized MNPs composite was confirmed with several analytical techniques. Importantly, nanoadsorbents exhibit high density of chelating amino groups and large magnetic force for easier separation. The importance of introduced bPEI, effect of pH, initial heavy metal concentration onto copper uptake efficiency and, further, nanoadsorbent regeneration, were studied and explained in detail. The adsorption isotherm was well fitted with Langmuir model, and the maximum adsorption capacity was shown to be 143 mg·g¹ for Cu2+. The reusability and superior properties of silica-coated MNPs functionalized with derived-bPEI for copper adsorption underlie its potential for the removal application from heavy metals contaminated sludge.

Surface-Attached Poly(oxanorbornene) Hydrogels with Antimicrobial and Protein-Repellent Moieties: The Quest for Simultaneous Dual Activity

By copolymerizing an amphiphilic oxanorbornene monomer bearing N- tert-butyloxycarbonyl (Boc) protected cationic groups with an oxanorbornene-functionalized poly(ethylene glycol) (PEG) macromonomer, bifunctional comb copolymers were obtained. Varying the comonomer ratios led to copolymers with PEG contents between 5⁻25 mol %. These polymers were simultaneously surface-immobilized on benzophenone-bearing substrates and cross-linked with pentaerythritoltetrakis(3-mercaptopropionate). They were then immersed into HCl to remove the Boc groups. The thus obtained surface-attached polymer hydrogels (called SMAMP*-co-PEG) were simultaneously antimicrobial and protein-repellent. Physical characterization data showed that the substrates used were homogeneously covered with the SMAMP*-co-PEG polymer, and that the PEG moieties tended to segregate to the polymer⁻air interface. Thus, with increasing PEG content, the interface became increasingly hydrophilic and protein-repellent, as demonstrated by a protein adhesion assay. With 25 mol % PEG, near-quantitative protein-adhesion was observed. The antimicrobial activity of the SMAMP*-co-PEG polymers originates from the electrostatic interaction of the cationic groups with the negatively charged cell envelope of the bacteria. However, the SMAMP*-co-PEG surfaces were only fully active against E. coli, while their activity against S. aureus was already compromised by as little as 5 mol % (18.8 mass %) PEG. The long PEG chains seem to prevent the close interaction of bacteria with the surface, and also might reduce the surface charge density.

Co-delivery of doxorubicin and methotrexate by dendritic chitosan-g-mPEG as a magnetic nanocarrier for multi-drug delivery in combination chemotherapy

Nanoparticulate drug delivery systems have the potential to improve the therapeutic efficacy of anticancer agents, and combination therapy is a promising strategy for clinical cancer treatment with synergistic effects.