Antimicrobial resistance (AMR) presents an escalating global challenge as conventional antibiotic treatments become less effective. In response, photodynamic therapy (PDT) and photothermal therapy (PTT) have emerged as promising alternatives. While rooted in ancient practices, these methods have evolved with modern innovations, particularly through the integration of lasers, refining their efficacy. PDT harnesses photosensitizers to generate reactive oxygen species (ROS), which are detrimental to microbial cells, whereas PTT relies on heat to induce cellular damage. The key to their effectiveness lies in the utilization of photosensitizers, especially when integrated into nano- or micron-scale supports, which amplify ROS production and enhance antimicrobial activity. Over the last decade, carbon dots (CDs) have emerged as a highly promising nanomaterial, attracting increasing attention owing to their distinctive properties and versatile applications, including PDT and PTT. They can not only function as photosensitizers, but also synergistically combine with other photosensitizers to enhance overall efficacy. This review explores the recent advancements in CDs, underscoring their significance and potential in reshaping advanced antimicrobial therapeutics.

Aberrant cell-surface sialylation is widely associated with cancer progression and provides an accessible molecular feature for biosensing and targeted delivery. However, engineering molecularly imprinted polymer nanoparticles (nanoMIPs) that combine selective sialic acid (SA) recognition with controlled degradability and cytocompatibility remains challenging. In this study, a simulation-guided strategy was used to develop hydrolytically degradable SA-imprinted nanoMIPs incorporating a functionalized lactose-based crosslinker with cleavable ester linkages. Molecular docking and quantum-chemical calculations identified N-isopropylacrylamide (NIPAM), acrylamide (AAm), and N-hydroxyethyl acrylamide (HEAA) as complementary functional monomers and established an optimized SA:NIPAM:AAm:HEAA molar ratio of 1:1:2:1. The resulting nanoMIPs were spherical and nanoscale and exhibited pH-dependent hydrolytic mass loss that was more pronounced under mildly acidic conditions than at physiological pH. Compared with non-imprinted nanoparticles, the nanoMIPs displayed substantially enhanced SA binding, with a maximum binding capacity of 89.38 μmol g⁻¹ and an imprinting factor of approximately 4.2, together with preferential recognition of SA over the selected competing molecules. MTT assays using MCF-7, HeLa, and HaCaT cells showed cell viability above 80% after 24 h exposure to 500 μg mL⁻¹, indicating favorable short-term cytocompatibility. By integrating computationally optimized, multicomponent SA recognition with a carbohydrate-derived, hydrolytically degradable crosslinking strategy, this work addresses the coupled requirements of binding-site fidelity and material degradability within a single nanoMIP platform. These findings establish a materials-level foundation for future SA-directed biosensing and targeted delivery systems in cancer-relevant applications.

Background/Objectives: Carbon dots (CDs) are promising antimicrobial nanomaterials owing to their biocompatibility, environmental friendliness, and tunable surface chemistry. This study aimed to synthesize nitrogen-doped CDs (AS-CDs) and develop a light-responsive antibacterial system through conjugation with chlorin e6 (Ce6). Methods: AS-CDs were synthesized by a microwave-assisted method using L-ascorbic acid and spermidine, followed by conjugation with Ce6. The materials were characterized by transmission electron microscopy, zeta potential analysis, and spectroscopic methods, and their antibacterial activity was evaluated against Escherichia coli, Staphylococcus aureus, and methicillin-resistant S. aureus (MRSA) under both dark and visible-light conditions. Cytotoxicity was assessed using HaCaT cells. Results: The AS-CDs exhibited a uniform nanoscale morphology with an average diameter of 6.3 nm and a positive surface charge of +15.6 mV, together with intrinsic broad-spectrum antibacterial activity. Ce6 conjugation further enhanced antibacterial efficacy under light irradiation, with the CDs-Ce6 conjugate achieving complete eradication of S. aureus and MRSA and marked inhibition of E. coli at 2.5 μg/mL. Cytotoxicity studies demonstrated low toxicity in HaCaT cells within the effective antibacterial concentration range. Conclusions: These findings highlight the potential of microwave-synthesized, photosensitizer-conjugated CDs as next-generation antimicrobial agents. This platform offers a cost-effective, sustainable, eco-friendly, and efficient platform for combating bacterial infections, with broader potential in pharmaceutical and biomedical applications.