Carbon nanogels exert multipronged attack on resistant bacteria and strongly constrain resistance evolution

Near-infrared light triggered upconversion nanocomposites with multifunction of enhanced antimicrobial photodynamic therapy and gas therapy for inflammation regulation

Antibacterial photodynamic therapy (aPDT) is highly effective in killing bacteria, while the problem of hypoxia and limited light penetration in deep tissue has not been properly solved. In addition, few aPDT works take into account the regulation of inflammation, which is an important regulatory process after antimicrobial therapy and the final purpose of treatment. In this work, to address the above isssues, we have designed a multi-functional composite UCNPs-Ce6-Mn(CO)5Br@Silane (referred to as UCM@Si), which consists of several key components: Up-conversion nanoparticles (UCNPs: NaErF4:Tm3+@NaYF4:Yb3+), Chlorin e6 (Ce6) and Manganese pentacarbonyl bromide (Mn(CO)5Br). When exposed to near-infrared (NIR) light (980 nm), the UCNPs can emit strong red light at 655 nm which further trigger the aPDT of Ce6. The generated reactive oxygen (ROS) subsequently break the metal carbonyl bond of Mn(CO)5Br, leading to the production of carbon monoxide (CO) molecules as well as manganese ions (Mn2+), which further decomposes hydrogen peroxide (H2O2) in the microenvironment to oxygen (O2). Therefore, this simple nanocomposite not only provides substantial self-oxygen replenishment for enhanced aPDT, but also facilitates effective inflammation regulation via CO across a wide range of deep infections. This approach leverages the unique properties of these materials to combat bacterial infections by simultaneously killing bacteria, regulating inflammation, and enhancing the oxygen levels in the affected microenvironment. This O2 and CO gas based aPDT treatment system offers a promising approach to comprehensively address microbial-induced infectious diseases, particularly deep infections, holding the potential clinical applications.

An Overview of the Potential of Food-Based Carbon Dots for Biomedical Applications

Food-based carbon dots (CDs) hold significant importance across various fields, ranging from biomedical applications to environmental and food industries. These CDs offer unique advantages over traditional carbon nanomaterials, including affordability, biodegradability, ease of operation, and multiple bioactivities. This work aims to provide a comprehensive overview of recent developments in food-based CDs, focusing on their characteristics, properties, therapeutic applications in biomedicine, and safety assessment methods. The review highlights the potential of food-based CDs in biomedical applications, including antibacterial, antifungal, antivirus, anticancer, and anti-immune hyperactivity. Furthermore, current strategies employed for evaluating the safety of food-based CDs have also been reported. In conclusion, this review offers valuable insights into their potential across diverse sectors and underscores the significance of safety assessment measures to facilitate their continued advancement and application.

Antibacterial Carbon Dots: Mechanisms, Design, and Applications

The increase in antibiotic resistance promotes the situation of developing new antibiotics at the forefront, while the development of non-antibiotic pharmaceuticals is equally significant. In the post-antibiotic era, nanomaterials with high antibacterial efficiency and no drug resistance make them attractive candidates for antibacterial materials. Carbon dots (CDs), as a kind of carbon-based zero-dimensional nanomaterial, are attracting much attention for their multifunctional properties. The abundant surface states, tunable photoexcited states, and excellent photo-electron transfer properties make sterilization of CDs feasible and are gradually emerging in the antibacterial field. This review provides comprehensive insights into the recent development of CDs in the antibacterial field. The topics include mechanisms, design, and optimization processes, and their potential practical applications are also highlighted, such as treatment of bacterial infections, against bacterial biofilms, antibacterial surfaces, food preservation, and bacteria imaging and detection. Meanwhile, the challenges and outlook of CDs in the antibacterial field are discussed and proposed.

Post-administration labeling with Palladium(II) ions enables ICP-MS-based determination of the biodistribution of carbonized nanogels

Carbonized nanogels (CNGs) are carbon-based nanomaterials possessing excellent antibacterial and antiviral activities for treating infectious diseases. Thus, investigations of the biodistribution of CNGs are crucial in ensuring their biosafety for in vivo applications. In this study, we combined a labeling scheme, employing tetrachloropalladate (PdCl₄^2-) ions to selectively label the administered CNGs in solubilized tissue samples, and an automatic sample pretreatment scheme, using a knotted reactor to effectively separate the PdCl₄^2--labeled CNGs from the free PdCl₄^2- ions and the tissue matrices, to enable reliable and interference-free quantification of CNGs through measuring the signal intensities of Pd using inductively coupled plasma mass spectrometry (ICP-MS). After optimizing the labeling conditions and the separation scheme, we observed that the PdCl₄^2- ions bound strongly to the CNGs (dissociation constant: 23.0 nM), with the method's detection limits reaching 1.6 fg L^-1 and 0.9 μg L^-1 within working ranges from 10^-4 to 1 μg L^-1 and from 1 to 1000 μg L^-1, respectively. We verified the reliability and applicability of this analytical method through spike analyses of solubilized rat liver, spleen, kidney, lung, brain, and blood samples (recoveries ranging from 96 to 102%) and through analyses of these rat organ and tissue samples after giving rats an intravenous dose of CNGs (2.5 mg kg^-1 body weight). The biodistribution data indicated that these administered CNGs deposited mainly in the liver, lung, and spleen at 10 min and 1 h post-administration. Our study revealed that this post-administration labeling scheme coupled with ICP-MS allows accurate determination of the biodistribution of carbonized nanomaterials.

Aminoglycoside-mimicking carbonized polymer dots for bacteremia treatment

Bacteremia and associated bacterial sepsis are potentially fatal and occur when the host response to microbial invasion is impaired or compromised. This motivated us to develop carbonized polymer dots (CPDs_Man/AA) from a mixture of mannose (Man) and positively charged amino acids [AAs; lysine, arginine (Arg), or histidine] through a one-step mild pyrolysis procedure, which effectively inhibited drug-resistant bacterial strains isolated from septic patients. The as-prepared CPDs_Man/AA showed broad-spectrum antibacterial activity, including multidrug-resistant bacteria, even in human plasma. The minimal inhibitory concentration of CPDs_Man/Arg is ca. 1.0 μg mL^-1, which is comparable to or lower than those of other tested antibiotics (e.g., ampicillin, gentamicin, and vancomycin). In addition to directly disrupting bacterial membranes, the CPDs_Man/Arg feature a structure similar to aminoglycoside antibiotics that could bind to 16S rRNA, thereby blocking bacterial protein synthesis. In vitro cytotoxic and hemolytic assays demonstrated the high biocompatibility of the CPDs_Man/AA. In addition, in vivo studies on methicillin-resistant Staphylococcus aureus-infected mice treated with the CPDs_Man/Arg showed a significant decrease in mortality-even better than that of antibiotics. Overall, the synthesis of the CPDs_Man/AA is cost-efficient, straightforward, and effective for treating bacteremia. The polymeric features of the CPDs_Man/Arg, including cationic charges and specific groups, can be recognized as a safe and broad-spectrum biocide to lessen our reliance on antibiotics to treat systemic bacterial infections in the future.

Recent Advances in Antimicrobial Nano-Drug Delivery Systems

Infectious diseases are among the major health issues of the 21st century. The substantial use of antibiotics over the years has contributed to the dissemination of multidrug resistant bacteria. According to a recent report by the World Health Organization, antibacterial (ATB) drug resistance has been one of the biggest challenges, as well as the development of effective long-term ATBs. Since pathogens quickly adapt and evolve through several strategies, regular ATBs usually may result in temporary or noneffective treatments. Therefore, the demand for new therapies methods, such as nano-drug delivery systems (NDDS), has aroused huge interest due to its potentialities to improve the drug bioavailability and targeting efficiency, including liposomes, nanoemulsions, solid lipid nanoparticles, polymeric nanoparticles, metal nanoparticles, and others. Given the relevance of this subject, this review aims to summarize the progress of recent research in antibacterial therapeutic drugs supported by nanobiotechnological tools.

How to evaluate the potential toxicity of therapeutic carbon nanomaterials? A comprehensive study of carbonized nanogels with multiple animal toxicity test models

Carbon-based nanomaterials have great potential in medical applications, especially in the treatment of infectious diseases and even tumors. However, to safely execute the application of carbon nanomaterials in human treatments, conducting safety assessments and establishing suitable evaluation criteria are necessary. In this study, lysine-carbonized nanogels (Lys-CNGs) that display antibacterial and antiviral abilities were employed in a comprehensive evaluation of their toxicity profiles through assessments in different animal models and growth stages. It was observed that zebrafish at the embryo and eleutheroembryo stages experienced significant toxic effects at a concentration of 15-fold the recommended dosage (0.5 ppm), whereas adult zebrafish following long-term consumption of fodder containing Lys-CNGs presented no adverse effects. Further microbiota analysis indicated that Lys-CNGs did not cause significant changes in the composition of the intestinal bacteria. In contrast, in the toxicity assessments with mammalian animal models, the Lys-CNGs showed no adverse effects, such as weight loss, dermal irritation, and skin sensitization responses in rabbits and guinea pigs, even at a high dose of 2000 mg/kg body weight. Our study revealed that Lys-CNGs have different toxic effects on different growth stages of zebrafish. Researchers in this field should carefully consider the implications of these toxicity profiles during the development of therapeutic carbon-based nanomaterials and for comparison of studies.

Carbon-based low-pressure filtration membrane for the dynamic disruption of bacteria from contaminated water

Carbon-based materials, especially graphene oxide (GO) and carbon dots possessing antibacterial properties, are widely used for various applications. Recently, we reported the antibacterial and antioxidant properties of carbonized nanogels (CNGs) for the treatment of bacterial keratitis, and as a virostatic agent against infectious bronchitis virus. In this work, we demonstrate the use of CNGs/GO nanocomposite (GO@CNGs) membrane for the efficient removal of Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria from contaminated water. The GO@CNGs composite membrane with an optimized ratio of GO to CNGs could achieve more than 99% removal efficiency toward E. coli and S. aureus. Various strains of bacteria interact differently with the membrane, and hence the membrane shows different removal rate, which can be optimized by controlling the interaction time through regulating the water flux. The GO@CNGs membrane with an active area of 2.83 cm² achieved > 99% bacterial removal efficiency at a water flux of 400 mL min^-1 m^-2. The dynamic disruption of bacteria by GO@CNGs plays a crucial role in eliminating the bacteria. Rather than filtering out the bacteria, GO@CNGs membrane allows them to pass through it, interact with the bacteria and rupture the bacterial cell membranes. Our GO@CNGs membrane shows great potential as a filter to remove bacteria from contaminated water samples, operating under tap water pressure without any extra power consumption.

Alleviation of dry eye syndrome with one dose of antioxidant, anti-inflammatory, and mucoadhesive lysine-carbonized nanogels

Most dry eye syndromes (DES) are caused by oxidative stress and an overactive inflammatory response, leading to tear deficiency and excessive tear evaporation. Conventional eye drops for DES treatment require high doses and frequent administration due to their insufficient precorneal residence time. To overcome these problems, in this study, we have developed carbonized nanogels (CNGs) via the straightforward pyrolysis of lysine hydrochloride (Lys) to provide a long-lasting eye drop formulation for topical DES therapy. This methodology thermally converts Lys-into nitrogen-doped crosslinked polymers with embedded nanographitic structures, which enable efficient free radical scavenging. The cationic and crosslinked polymeric features of the Lys-CNGs also prolong the precorneal retention time and improve ocular bioavailability. These Lys-CNGs exhibit high biocompatibility with corneal epithelial cells both in vitro and in vivo, indicating their safety as eye drops. In a DES rabbit model, a single dose of Lys-CNGs (50 µg mL^-1) can effectively alleviate the signs of DES within 4 days, whereas multiple treatments of 10-fold higher concentration of cyclosporine A are needed to achieve similar therapeutic effects (one dose every 12 h; 500 µg mL^-1). The topical administration of Lys-CNGs enable a reduced therapeutic dose and extended dosing interval, thereby demonstrating a superior therapeutic efficacy compared to the commercial cyclosporine A eye drops. These Lys-CNGs, which exhibit significant free radical scavenging, anti-inflammatory activity, high biocompatibility, and a remarkable ocular bioadhesive property, hold great potential as a long-lasting eye drop formulation for the treatment of dry eye disease. STATEMENT OF SIGNIFICANCE: Multifunctional nanobiomaterial-based eye drops can render an ideal pharmaceutical formulation for the treatment of a variety of ocular surface diseases. To our knowledge, this is the first report describing the development of carbonized nanogels as topically administered therapeutics for alleviating dry eye syndrome (DES). We present evidence that the thermal transformation of lysine hydrochloride into carbonized nanogels (Lys-CNGs) endows superior antioxidant, anti-inflammatory, and bioadhesive properties. While a single dose of Lys-CNGs (50 µg mL^-1) is sufficient to relieve the symptoms of DES for 4 days, multiple treatments of 10-fold higher concentration of commercially available cyclosporine eye drops are needed to achieve similar therapeutic outcomes (one dose every 12 h; 500 µg mL^-1), suggesting an effective and long-lasting ocular carbonized nanomedicine.