Programmable Protein Crystal Platform for Precision Molecular Delivery and Advanced Biomaterials

At a Glance

Researchers at Colorado State University have developed porous protein crystals that can store, organize, and release many types of molecules. These crystals can hold DNA, enzymes, and nanoparticles with controlled placement. Their structure stays the same across different sizes, making them reliable and scalable. They also support controlled loading and release over time. This platform can be used for drug delivery, sensing, and advanced materials.

Background

Biological scaffolds such as protein cages and nucleic acid assemblies can organize molecules at the nanoscale but often lack structural uniformity and tunability at larger scales. Porous protein crystals overcome these limitations by maintaining identical internal architecture regardless of size while providing large, accessible nanopores. Historically, challenges in protein crystallization and characterization limited their use in materials science. Recent advances now enable these crystals to function as programmable platforms for molecular transport, storage, and integration of functional materials, making them highly relevant for drug delivery, sensing, and nanotechnology.

Overview

This technology consists of engineered porous protein crystals with uniform nanopores (~13 nm) that enable controlled loading and spatial organization of a wide range of guest materials, including nucleic acids, enzymes, nanoparticles, and polymers. The crystals can be synthesized across a wide size range while maintaining consistent internal structure, allowing reproducible performance and scalable fabrication.

The material exhibits strong and tunable interactions with guest molecules, particularly nucleic acids, with reported adsorption affinities on the order of ~200 L/g. This high binding affinity enables substantial loading and strong retention of guest molecules within the pore network. Loading can be improved and tuned by adjusting pore surface chemistry, solution conditions (pH, ionic strength), and guest properties (size, charge), which influence adsorption affinity and distribution within the pore network. Release is triggered by environmental changes (e.g., pH) that weaken guest–scaffold interactions, enabling controlled unloading.

The scaffold also supports integration of functional materials within its pore structure. Metal–organic frameworks (MOFs) can be synthesized directly inside the pores, forming composite systems that combine structural organization with catalytic or sensing functionality.

Figure 1. Porous protein crystal structure and DNA loading. (A) Hexagonal protein crystals. (B) Internal structure showing ~13 nm pores that run through the crystal. A DNA molecule is shown for scale. (C) Schematic of DNA being added to the crystal for loading and observation.

Figure 2. (A) The porous protein crystal loaded with fluorescently tagged enzyme. (B) Four unit cells of the protein crystal with a single fluorescent guest molecule modelled in the large nanopore. (C) A schematic of crystal pores and axes.

Figure 3. Three samples of protein crystals were loaded with horseradish peroxidase (hHRP) and the concentration of adsorbed hHRP into the crystal is calculated over time.

Benefits

Large ~13 nm pores enable loading of macromolecules beyond conventional nanoporous limits
Dual-scale porosity (~13 nm and ~3 nm) supports selective and multi-type molecule loading
Tunable size range from 100 nm to 1 mm enables use across nano- to bulk-scale applications
Demonstrated compatibility with 10+ material classes including DNA, proteins, and nanoparticles
Integration of functional nanomaterials (e.g., MOFs) for catalytic or sensing capabilities
Strong adsorption of DNA (~200 L/g) enables stable storage
Controlled and triggerable release (e.g., pH-responsive)
Spatially controlled placement within the crystal lattice
Scalable crystal growth with consistent internal structure
Biodegradable and biocompatible in biological environments