Natamycin is a tetraene polyene that exploits its antifungal properties by irreversibly binding components of fungal cell walls, blocking the growth of infections. However, topical ocular treatments with natamycin require frequent application due to the low ability of this molecule to permeate the ocular membrane. This limitation has limited the use of natamycin as an antimycotic drug, despite it being one of the most powerful known antimycotic agents. In this work, different lipidic nanoformulations consisting of transethosomes or lipid nanoparticles containing natamycin are proposed as carriers for optical topical administration. Size, stability and zeta potential were characterized via dynamic light scattering, the supramolecular structure was investigated via small- and wide-angle X-ray scattering and 1H-NMR, and the encapsulation efficiencies of the four proposed formulations were determined via HPLC-DAD.

The surface properties of drug containers should reduce the adsorption of the drug and avoid packaging surface/drug interactions, especially in the case of biologically-derived products. Here, we developed a multi-technique approach that combined Differential Scanning Calorimetry (DSC), Atomic Force Microscopy (AFM), Contact Angle (CA), Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), and X-ray Photoemission Spectroscopy (XPS) to investigate the interactions of rhNGF on different pharma grade polymeric materials. Polypropylene (PP)/polyethylene (PE) copolymers and PP homopolymers, both as spin-coated films and injected molded samples, were evaluated for their degree of crystallinity and adsorption of protein. Our analyses showed that copolymers are characterized by a lower degree of crystallinity and lower roughness compared to PP homopolymers. In line with this, PP/PE copolymers also show higher contact angle values, indicating a lower surface wettability for the rhNGF solution on copolymers than PP homopolymers. Thus, we demonstrated that the chemical composition of the polymeric material and, in turn, its surface roughness determine the interaction with the protein and identified that copolymers may offer an advantage in terms of protein interaction/adsorption. The combined QCM-D and XPS data indicated that protein adsorption is a self-limiting process that passivates the surface after the deposition of roughly one molecular layer, preventing any further protein adsorption in the long term.

In this review, we discuss the progress in the investigation of macromolecular crystals obtained through the use of atomic force microscopy (AFM), a powerful tool for imaging surfaces and specimens at high resolution. AFM enables the visualization of soft samples at the nanoscale and can provide precise visual details over a wide size range, from the molecular level up to hundreds of micrometers. The nonperturbative nature, the ability to scan in a liquid environment, and the lack of need for freezing, fixing, or staining make AFM a well-suited tool for studying fragile samples such as macromolecular crystals. Starting from the first morphological investigations revealing the surface morphology of protein crystals, this review discusses the achievements of AFM in understanding the crystal growth processes, both at the micro- and nanoscale. The capability of AFM to investigate the sample structure at the single molecular level is analyzed considering in-depth the structure of S-layers. Lastly, high-speed atomic force microscopy (HS-AFM) is discussed as the evolution to overcome the limitations of low imaging speed, allowing for the observation of molecular dynamics and weakly adsorbed, diffusing molecules. HS-AFM has provided intuitive views and directly visualized phenomena that were previously described indirectly, answering questions that were challenging to address using other characterization methods.

Nerve growth factor (NGF) plays a critical neuroprotective role in retinal health, supporting neuronal survival and regeneration. Recombinant human NGF (rhNGF) holds promise for treating retinal degenerative diseases such as glaucoma, retinitis pigmentosa, and optic neuropathies. However, efficient retinal delivery of rhNGF remains a major challenge due to anatomical barriers and rapid clearance from conventional routes. Here, we integrate in vivo experimentation with mathematical modeling to identify and validate optimized delivery strategies for rhNGF. By using stable isotope-labeled rhNGF, we quantified ocular biodistribution in rats and rabbits following topical eye drops, intravitreal (IVT) injections, and sustained-release formulations. Eye drop administration resulted in negligible retinal exposure (<0.04% of instilled dose), while IVT injection achieved ∼34% vitreous retention with sustained delivery to the retina and optic nerve over 60 days. A mechanistic compartmental model was developed and validated against the in vivo data to simulate route-specific drug transport and estimate delivery losses via a penalty factor (fB). The model identified key parameters governing retinal exposure and guided the design of dose-release profiles to sustain therapeutic concentrations. Controlled-release platforms, such as bioadhesive tablets and gels, exhibited in vitro release rates (0.002–0.015 h⁻¹) aligned with model-predicted requirements for prolonged exposure. Together, these results highlight the importance of route-specific delivery design and demonstrate that combining isotope tracing with mechanistic modeling can quantitatively guide development of long-acting retinal therapeutics. This platform provides a translational framework for optimizing macromolecular drug delivery to the posterior eye.