How 3D electron diffraction solved lutein – and enabled a landmark patent

Wed, 20.05.2026

PCT patent WO 2025/106389 A1, published May 2025, discloses novel crystalline and cocrystal forms of lutein with improved stability and bioavailability. To our knowledge, it is also the first published patent to contain crystallographic data measured on the ELDICO ED-1.

The patent was filed by a consortium comprising our partner TeraСrystal SRL (Cluj-Napoca, Romania), Iuliu Hațieganu University of Medicine and Pharmacy (Romania), and the Board of Supervisors of Louisiana State University and Agricultural and Mechanical College (USA). The structural characterization at the core of the work was carried out using three-dimensional electron diffraction (3D-ED) on the ED-1 — at room temperature.

The compound: useful, but analytically uncooperative

Lutein is a xanthophyll carotenoid — a plant pigment with a sequence of ten conjugated carbon-carbon double bonds. It accumulates in the inner retinal layer of the human macula, where it absorbs short-wavelength blue light and acts as a primary antioxidant. There is consistent evidence linking dietary lutein intake to reduced risk of age-related macular degeneration (AMD) and cataracts.

Pharmaceutical exploitation of that protective activity has been constrained by the compound’s physicochemical properties. Lutein is water-insoluble, poorly absorbed in vivo, and — critically for solid-state characterization — chemically fragile. It degrades under light, oxygen, and heat. In practice, it is stored at −20°C to prevent degradation. Growing single crystals of sufficient quality for laboratory X-ray diffraction is extraordinarily difficult: the molecule’s hydrophobic character, sensitivity to oxidation, and slow nucleation kinetics combine to produce only small, poorly-formed crystals.

As a result, prior crystal structure determinations of lutein had only been achieved for solvated forms — structures incorporating ethanol or methanol into the crystal lattice, measured at cryogenic temperatures (113 K). Those solvent interactions alter the molecule’s conformation, causing twisting and bending of the polyene chain that does not reflect the behaviour of pure lutein in its solid pharmaceutical form.

Why 3D-ED — and why the ED-1 specifically

Three-dimensional electron diffraction is the natural tool for this problem. Electrons interact with matter far more strongly than X-rays, which means complete structural datasets can be obtained from nanocrystalline samples orders of magnitude smaller than those required for single-crystal XRD. For a compound that forms small, fragile crystals, this is a practical necessity, not just a technical preference.

The ELDICO ED-1 is a dedicated electron diffractometer — not a repurposed transmission electron microscope — purpose-built for organic and pharmaceutical materials. It operates at low accelerating voltage with a parallel beam, minimising beam-induced damage to sensitive compounds, and its sensitive hybrid-pixel detector captures the weak scattering signals typical of small organic crystals. STEM-mode imaging allows suitable nanocrystals to be identified and centred before data collection begins.

For a material as heterogeneous and fragile as lutein, that combination — controlled illumination, sensitive detection, and the ability to select suitable crystals before committing to a dataset — is what makes the experiment tractable.

The experiment: minimal preparation, complete result

Sample preparation was straightforward. A small amount of crystalline lutein powder was gently ground between two glass slides. A carbon-coated 300-mesh copper TEM grid was placed on top of the sample and pressed gently to transfer material. The grid was loaded into the ED-1. An optical microscope confirmed that material had been deposited correctly.

The motorised stage allowed translation and rotation with sub-micrometre precision. Using STEM mode, a suitable nanocrystal was identified and centred in the beam. Diffraction data were collected in 0.5° increments as the crystal was continuously rotated over a 120° range. CrysAlisPro was used for unit cell determination and intensity extraction. The crystal structure was solved with Olex2.

No cryogenic sample handling. No solvent inclusion. A compound that normally lives at −20°C, measured at 293 K — and a complete crystal structure as the result.

The structure: compact, stable, and genuinely new

The result was a triclinic crystal structure: space group P-1, unit cell dimensions a = 8.363 Å, b = 9.019 Å, c = 12.943 Å, α = 81.05°, β = 74.61°, γ = 86.32°, unit cell volume 929.5 ų, Z = 1. The structure was determined at 293 K — the first crystal structure of solvent-free, pure crystalline lutein measured at or near ambient conditions.

The newly determined structure shows no crystallographic similarity to the previously reported ethanol and methanol solvates. In the solvate structures, solvent molecules occupy voids in the crystal lattice and interact with the lutein polyene chain, causing conformational changes that distort the molecule away from its equilibrium geometry. The unsolvated crystalline form shows a more fixed, extended conformation.

The packing is notably compact. Solvent-accessible voids account for less than 0.5% of total unit cell volume — insufficient to accommodate even a single water molecule. This dense packing maximises intermolecular interactions and directly explains the improved physical stability of the new polymorph under accelerated degradation conditions.

Validation was straightforward: the XRPD pattern calculated from the ED-derived crystal structure matches the experimentally recorded powder diffraction pattern of the bulk crystalline material. The nanocrystal structure is representative of the material at scale.

From structure to pharmaceutical application

The crystal structure determination is the foundation, but the patent extends well beyond it. Using the ED-derived structural understanding of pure crystalline lutein, the research team developed four new cocrystal forms — with gallic acid, gentisic acid, 5-hydroxytryptophan (5-HTP), and DL-α-tocopherol — and characterised each by XRPD and differential scanning calorimetry.

In vitro diffusion testing showed substantially higher lutein concentrations in the receiving compartment for all crystalline and cocrystal forms compared with unprocessed lutein (113 ng/mL after 48 h). The lutein–gallic acid cocrystal reached 2,368 ng/mL — approximately 20-fold higher. Crystalline lutein alone reached 783 ng/mL, a 7-fold improvement.

In vivo, the results are equally clear. In a selenite-induced cataract model in rat pups, topical application of crystalline lutein in a bioadhesive hydrogel reduced mean cataract severity by approximately 70% compared to untreated control (p < 0.001). Of the three cocrystal forms tested in this model (gallic acid, gentisic acid, and 5-HTP), each showed reductions of approximately 54–57% (p < 0.001). Human applications — topical ocular formulations for AMD, diabetic retinopathy, and cataract prevention — are the stated direction.

What this means for electron diffraction in pharmaceutical development

This patent demonstrates what 3D-ED can do in pharmaceutical solid-state work when the right instrument is used: a compound that defeats conventional single-crystal XRD, measured under ambient conditions, yields a complete and validated crystal structure in a single dataset. That structure supports polymorph characterisation, cocrystal development, and patent claims — across a full CMC workflow.

For ELDICO, WO 2025/106389 A1 is, to our knowledge, the first published patent to include crystallographic data from the ED-1. We expect it will not be the last.

Congratulations to TeraСrystal and all collaborators on this work.

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Patent reference: WO 2025/106389 A1 (PCT/US2024/055434), published 22 May 2025
Instrument: ELDICO ED-1 electron diffractometer
Partners: TeraСrystal SRL (Romania) · Iuliu Hațieganu University of Medicine and Pharmacy · Louisiana State University (USA)
Crystallographic data: P-1, a = 8.363 Å, b = 9.019 Å, c = 12.943 Å, V = 929.5 ų, Z = 1, T = 293 K