A research team at the Technical University of Munich (TUM) has created hollow microspheres using a combination of mucin and polydopamine, aiming to develop a new system for targeted and sustained drug delivery. Designed to adhere to difficult biological surfaces such as cartilage and the oral mucosa, the microspheres have been shown to retain their structure and gradually release their therapeutic cargo.
The work, published in Small and led by Oliver Lieleg, professor of biopolymer materials at TUM, builds on the multifunctional characteristics of mucin, the group of large glycoproteins that are a key component in many protective mucosal barriers in the human body, such as the oral mucosa and stomach. Combined with polydopamine, a polymer inspired by the adhesive proteins of mussels, the resulting microspheres demonstrate both stickiness and structural versatility.
The microspheres were developed through a core-shell process. A core material is first coated with layers of mucin and polydopamine. Once the core is dissolved, a hollow, porous sphere remains. According to the team, this method overcomes a common limitation in similar production approaches where spheres collapse after core removal.
Importantly, the spheres maintain a porous structure that allows small molecules to diffuse in. This enables the post-production loading of therapeutic substances. The release profile of the cargo can then be adjusted by adding a sealing component to the surface of the sphere.
In one experimental variant, silver ions were used to partially seal the microsphere shell. This strategy was effective in slowing cargo release while preserving the overall structure of the sphere. The team also demonstrated that silver ion inclusion altered the biological impact of the spheres in cell models, promoting cytotoxic effects which may be of interest in applications such as cancer therapy.
The type of sealing agent and the biological environment in which the microspheres are deployed play a central role in determining their function. When silver ions were present, the spheres exhibited cytotoxic effects in cell cultures. Without silver, the anti-inflammatory properties of polydopamine became more prominent, protecting cells under chemically induced stress.
These findings suggest potential applications in conditions such as osteoarthritis or oral injuries, where local inflammation is a factor. The lubricating properties of mucin could also support protective roles within joints or on mucosal surfaces.
The research highlights how combinations of natural and synthetic polymers can be used to design drug delivery vehicles with multiple, adjustable functions. While the study was limited to laboratory and animal tissue experiments, it supports further investigation of these materials in more complex biological systems.
Reference: Fan D, Gunnella C, Wang Y, et al. Multi‐functional polydopamine‐mucin hollow particles provide tunable shell permeability, ros scavenging, tissue adhesion, and lubricity for biomedical applications. Small. 2025;21(34):2503238. doi: 10.1002/smll.202503238
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