Pathogen infections constitute a serious problem in the field of lung diseases, especially in severe conditions such as chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS). Exacerbations of COPD and ARDS can be significantly influenced by bacterial infections from Pseudomonas aeruginosa and Staphylococcus aureus, which can hasten the decline of lung function. Moreover, the abuse of high-dose antibiotics used to treat obstinate infections is contributing to the growing issue of multidrug resistance (MDR) by microorganisms. Currently, new therapeutic strategies capable of surprising and fighting pathogens with new modalities are missing. In this framework, bio-composite nanogels (NGs) based on natural polymers with intrinsic antimicrobial properties such as chitosan (CS) and hyaluronic acid (HA) have been developed for the treatment of lung infections. The DLS and TEM results showed that NGs have a spherical shape with a size smaller than 100 nm, making it possible for them to potentially reach the lung site and evade the clearance of alveolar macrophages. FTIR spectra demonstrated that only electrostatic interactions, not chemical reactions, occur between NG precursors. Rheological analysis highlighted NGs’ injectability and mucoadhesive capacity. Moreover, an MTT assay on human lung fibroblast cells for biocompatibility evaluation showed good viability up to 48 h. Finally, an antimicrobial test on P. aeruginosa and S. aureus showed an increase in antimicrobial activity as the NG concentration increases, with a reduction in bacterial growth of around 60% at 375 μg/mL.

Bacterial infections are a major complication in chronic obstructive pulmonary disease (COPD) and acute respiratory distress syndrome (ARDS), where mucus accumulation and pH fluctuations further hinder treatment. Nanostructured systems such as carbon dots (CDs) are increasingly investigated as antimicrobial agents due to their scalability, low cost, and biocompatibility, compared to conventional antibiotics. Here, CDs were synthesized by a one-step microwave-assisted method at three reaction temperatures (130 °C, 170 °C, and 185 °C, named LT-CDs, MT-CDs, HT-CDs, respectively) to explore the effect of carbonization on their structure and function. TEM, Raman, and FTIR analyses were employed to investigate the size and distribution of carbon groups. UV–vis confirmed distinct pH-dependent spectral responses, and mucoadhesion studies revealed stronger and more stable interactions for MT-CDs. Biological assays demonstrated high biocompatibility across all samples on lung fibroblasts, while antimicrobial tests highlighted a selective effect against Staphylococcus aureus, due to ROS generation. Overall, MT-CDs represented the best compromise in terms of size, functionalization, biocompatibility, mucoadhesion, and antimicrobial activity, emerging as promising nanoplatforms for respiratory infection management in COPD and ARDS.

Drug-free chitosan/hyaluronic acid nanoparticles resolve the mucosal retention-penetration trade-off via a time-dependent transition, combining dynamic mucus interaction with antioxidant, biocompatible, and intrinsic antimicrobial activity.