Title : Non-crystalline stabilization of iron-oxide nanoparticles enables a versatile platform for carrier-dependent and carrier-free drug delivery
Abstract:
We investigated alternative routes for tuning nanoparticle drug-delivery behavior by deliberately disrupting spinel lattice formation during iron-oxide: magnesium synthesis. Under constrained, automation-compatible co-precipitation conditions, defective ferrite assembly prevented crystallinity from governing particle organization. Process-integrated analytics showed that oxygen-limited environments yielded compositionally altered yet colloidally stable particles, marked by reduced magnesium incorporation and direct integration of low-molecular-weight dextran during nucleation rather than through post-synthetic adsorption. Multidentate iron-coordination ligands were required to maintain colloidal integrity. Optical measurements further revealed kinetic signatures incompatible with spinel crystallization, instead indicating the emergence of a locked, non-crystalline colloidal state.
Recent advances in drug delivery have highlighted carrier-free or minimally structured systems in which the therapeutic molecule itself drives nanoparticle formation or stabilization, thereby reducing formulation complexity, toxicity, and regulatory burden. Drug nanocrystals exemplify this approach by organizing the active ingredient into nanoscale colloidal domains with near-quantitative loading and accelerated dissolution. Biocompatible self-assembled nanoparticles, stabilized through reversible noncovalent interactions such as hydrogen bonding and electrostatic association, enable bioactive molecules to form supramolecular architectures without chemical modification. Metal–biomolecule networks (MBNs) extend this paradigm by coordinating metal ions with endogenous biomolecules to generate spacious, cage-free frameworks capable of associating therapeutics without synthetic carriers.
Our results demonstrate that robust colloidal stabilization can be achieved without enforcing crystallinity, supporting the creation of a standardized iron-oxide nanoparticle library suitable for combinatorial screening and therapeutic development. The two resulting classes (Type I and Type II) display distinct physicochemical profiles consistent with single particles possessing different composite dimensions and component ratios. Type I organic nanoparticles showed enhanced freeze–thaw resilience, whereas Type II formulations improved cellular viability.
These emerging modalities collectively underscore the importance of determining when conjugation is necessary for effective delivery of proteins, nucleic acids, and small molecules in vitro. To address this, we evaluated two delivery strategies using Type II formulations: (i) antibody-conjugated nanoparticles generated through primary-amine coupling, assessed alongside their unconjugated counterparts, and (ii) small-molecule–conjugated nanoparticles produced via click-chemistry labeling, benchmarked against uncoupled, carrier-free loading of therapeutics. Together, these findings illustrate how non-crystalline, ligand-stabilized nanoparticles provide a versatile platform spanning both carrier-independent and conjugation-dependent drug-delivery modalities.
