PEGylation of Nanosubstrates (Titania) with Multifunctional Reagents: At the Crossroads between Nanoparticles and Nanocomposites

Abstract

Titania (anatase) nanoparticles were successfully PEGylated through the use of catechol (dopamine)-terminated PEG derivatives. The resulting materials were characterized by excellent stability at neutral pH and extremely low toxicity (phagocytic and nonphagocytic cell lines). In particular, we focused on the comparison between mono-and bis-catechol PEGs. Due to the double terminal anchorage on the titania surface, bis-catechol ligands can produce chains differing from classical monoanchored PEG in conformation (horseshoe-shaped vs brush) and thus the possibility of interactions with biomolecules. At the same time, less than quantitative catechol binding may lead to the presence of dangling chains with unbound catechols which can polymerize and eventually produce PEG/titania nanocomposite colloids. Our results on double-functional PEG2000 show the latter to be the case. Pluronic F127 was also used as a bifunctional ligand, leading to nanocomposite aggregates with an even larger organic content.

Impact of surface curvature, grafting density and solvent type on the PEGylation of titanium dioxide nanoparticles

“…Ma et al [36] PEGylated silica nanoparticles in water; Yang et al [40], Liu et al [41] and Cano et al [42] used the same solvent for PEGylation of iron oxide nanoparticles. Water is the preferred solvent also for TiO 2 nanoparticles functionalization, as reported in many different works [15,16,37,43].…”

“…In any grafting process, two are the key factors: (i) the choice of the linker used to chemically attach the polymer to the surface and (ii) the choice of the solvent in which the grafting process takes place during the synthesis. Thiol/silane [35,36], catechol [37,38], carbonyl/carboxyl [15] or phosphate [39] modified PEG are typically chosen as linker functionalities. Different solvents can be used as medium for the polymer grafting process on metal oxide nanoparticles, however water is the most popular one, due to the foreseen biomedical applications.…”

Intracellular in situ labeling of TiO2 nanoparticles for fluorescence microscopy detection

“…A high-affinity covalent bond is created between the nanoparticles and enediol ligands (e.g., alizarin and dopamine), thereby forming stable complexes. This unique feature has been exploited in coating these nanoparticles with various agents [1, 3, 4, 7–21]. …”

Water‐Dispersible, Ligand‐Free, and Extra‐Small (<10 nm) Titania Nanoparticles: Control Over Primary, Secondary, and Tertiary Agglomeration Through a Modified “Non‐Aqueous” Route

“…In a previous paper, we have employed a non‐aqueous process in benzyl alcohol, where TiCl 4 and ethanol in situ produce Ti(Cl) 4– n (OEt) n ( n close to four), whose thermal condensation at 80 °C eventually produced anatase nanoparticles with a virtually ligand‐free surface and an average diameter in the region of 30 nm . The nanoparticles can then be easily functionalized, for example, with catechols, possibly bearing also PEG chains . In addition to the typical advantages of non‐aqueous processes, this “benzyl alcohol method” allows the preparation of ligand‐free nanoparticle dispersions in acidic water, due to the contemporaneous and rapid occurrence of the hydrolysis of alkoxide surface groups and of the surface protonation, which allows electrostatic stabilization.…”