A New Strategy to Reduce Hospital-Acquired Infections - Biodegradable Antibacterial Nanostructured Coatings

Healthcare-associated infections (HAIs) remain a major global challenge. Pathogenic microorganisms can persist for extended periods on high-touch surfaces, contributing to the spread of infections in clinical environments. Conventional cleaning and disinfection procedures provide only temporary protection, creating a growing demand for materials capable of delivering continuous antimicrobial activity directly at the surface.

A recent study presents an innovative approach based on biodegradable nanostructured coatings using chitosan and poly(ε-caprolactone) (PCL), incorporating chlorhexidine-loaded zirconium phosphate nanoparticles. The objective is to combine sustained antibacterial performance with good cytocompatibility, mechanical stability, and environmental sustainability.

Mechanism of Action: Biopolymer Matrix Combined with a Nanostructured Active Filler

At the core of the system is a hybrid nanofiller based on zirconium hydrogen phosphate (ZrP). Its lamellar structure enables the intercalation of chlorhexidine molecules, resulting in controlled release and enhanced thermal stability of the active compound.

This nanostructured architecture offers several advantages:

• Stabilization and protection of chlorhexidine
• Controlled and prolonged release
• Good compatibility with polymer matrices
• Homogeneous dispersion within the coating system

The nanoscale organization increases the effective surface area and enhances interaction with microbial cells.

Chitosan Used in the Study - Characteristics and Suitable Alternatives

The study employed medium-molecular-weight chitosan with a degree of deacetylation of approximately 77 %.

This specific grade provides a well-balanced combination of:

• Film-forming capability
• Mechanical stability
• Processability in aqueous systems
• Intrinsic antimicrobial activity

Chitosan itself contributes to antibacterial performance due to its cationic nature, enabling electrostatic interaction with negatively charged bacterial membranes.

Alternative Chitosan Grades for Industrial Applications

Depending on the target application, different chitosan types may be considered:

Medium molecular weight (as used in the study)
→ Good balance between mechanical strength and processability
→ Suitable for spray or coating applications
Low molecular weight chitosan
→ Improved solubility
→ More uniform thin film formation
→ Attractive for drug-release coatings
High molecular weight chitosan
→ Enhanced mechanical robustness
→ Stronger barrier properties
Chemically modified chitosan (e.g., carboxymethylated or quaternized chitosan)
→ Improved water solubility
→ Increased antimicrobial activity
→ Tunable surface functionality

The selection of chitosan grade should therefore be guided by the desired release profile, adhesion behavior, hydrophilicity, and mechanical requirements.

Coating Design and Application

The nanocomposite formulations were dispersed in polymer solutions and applied onto polypropylene substrates. Chitosan-based coatings were deposited via spray techniques, while PCL-based systems were applied by brush coating. The resulting films exhibited uniform thickness in the micrometer range and strong adhesion to the substrate.
Structural and surface analyses confirmed:

• Homogeneous nanoparticle distribution
• Stable polymer backbone integrity
• Tunable surface wettability
• Excellent adhesion performance

The coatings also demonstrated resistance to water exposure and repeated cleaning cycles, while maintaining controlled removability depending on the polymer matrix.

Antibacterial Performance

Both coating systems exhibited pronounced antibacterial activity against clinically relevant pathogens, including multidrug-resistant strains from the ESKAPE group.

PCL-based coatings showed a particularly rapid bactericidal effect, achieving significant log-reductions within one hour of contact across all tested strains.

Chitosan-based coatings also demonstrated strong antibacterial performance. While the onset of action was slightly slower for certain Gram-positive strains, significant reductions were observed within one to two hours.
The combined effects of:

• Intrinsic antimicrobial activity of chitosan
• Controlled chlorhexidine release from the nanostructured filler
• Enhanced surface-microorganism interaction

result in sustained and effective microbial load reduction.

Outlook and Industrial Relevance

The findings highlight the strong potential of biodegradable nanostructured coatings as active antimicrobial surfaces for high-touch environments, particularly in healthcare settings.

In addition to reducing the risk of healthcare-associated infections, these systems offer:

• Biocompatibility
• Environmental sustainability
• Controlled renewability
• Adaptability to different substrates

Chitosan, in particular, provides a versatile platform material due to its natural origin, intrinsic antimicrobial properties, and chemical modifiability.

Such nanocomposite coatings represent a promising strategy for next-generation infection control technologies.

Reference
Stanzione, M., Improta, I., Raucci, M. G., Soriente, A., Lavorgna, M., Buonocore, G. G., Spogli, R., Marcelloni, A. M., Proietto, A. R., Amori, I., Mansi, A.: Biodegradable Antibacterial Nanostructured Coatings on Polypropylene Substrates for Reduction in Hospital Infections from High-Touch Surfaces. Nanomaterials 2026, 16(2), 80. Doi: 10.3390/nano16020080

First published on 12th of march 2026

Revised on 12th of march 2026