ROS generating BODIPY loaded nanoparticles for photodynamic eradication of biofilms.

Bacterial biofilms can pose a serious health risk to humans and are less susceptible to antibiotics and disinfection than planktonic bacteria. Here, a novel method for biofilm eradication based on antimicrobial photodynamic therapy utilizing a nanoparticle in conjunction with a BODIPY derivative as photosensitizer was developed. Reactive oxygen species are generated upon illumination with visible light and lead to a strong, controllable and persistent eradication of both planktonic bacteria and biofilms. One of the biggest challenges in biofilm eradication is the penetration of the antimicrobial agent into the biofilm and its matrix. A biocompatible hydrophilic nanoparticle was utilized as a delivery system for the hydrophobic BODIPY dye and enabled its accumulation within the biofilm. This key feature of delivering the antimicrobial agent to the site of action where it is activated resulted in effective eradication of all tested biofilms. Here, 3 bacterial species that commonly form clinically relevant pathogenic biofilms were selected: Escherichia coli, Staphylococcus aureus and Streptococcus mutans. The development of this antimicrobial photodynamic therapy tool for biofilm eradication takes a promising step towards new methods for the much needed treatment of pathogenic biofilms.

Analytical and toxicological aspects of nanomaterials in different product groups: Challenges and opportunities.

The widespread integration of engineered nanomaterials into consumer and industrial products creates new challenges and requires innovative approaches in terms of design, testing, reliability, and safety of nanotechnology. The aim of this review article is to give an overview of different product groups in which nanomaterials are present and outline their safety aspects for consumers. Here, release of nanomaterials and related analytical challenges and solutions as well as toxicological considerations, such as dose-metrics, are discussed. Additionally, the utilization of engineered nanomaterials as pharmaceuticals or nutraceuticals to deliver and release cargo molecules is covered. Furthermore, critical pathways for human exposure to nanomaterials, namely inhalation and ingestion, are discussed in the context of risk assessment. Analysis of NMs in food, innovative medicine or food contact materials is discussed. Specific focus is on the presence and release of nanomaterials, including whether nanomaterials can migrate from polymer nanocomposites used in food contact materials. With regard to the toxicology and toxicokinetics of nanomaterials, aspects of dose metrics of inhalation toxicity as well as ingestion toxicology and comparison between in vitro and in vivo conclusions are considered. The definition of dose descriptors to be applied in toxicological testing is emphasized. In relation to potential exposure from different products, opportunities arising from the use of advanced analytical techniques in more unique scenarios such as release of nanomaterials from medical devices such as orthopedic implants are addressed. Alongside higher product performance and complexity, further challenges regarding material characterization and safety, as well as acceptance by the general public are expected.

Monitoring and imaging pH in biofilms utilizing a fluorescent polymeric nanosensor.

Biofilms are ubiquitous in nature and in the man-made environment. Given their harmful effects on human health, an in-depth understanding of biofilms and the monitoring of their formation and growth are important. Particularly relevant for many metabolic processes and survival strategies of biofilms is their extracellular pH. However, most conventional techniques are not suited for minimally invasive pH measurements of living biofilms. Here, a fluorescent nanosensor is presented for ratiometric measurements of pH in biofilms in the range of pH 4.5-9.5 using confocal laser scanning microscopy. The nanosensor consists of biocompatible polystyrene nanoparticles loaded with pH-inert dye Nile Red and is surface functionalized with a pH-responsive fluorescein dye. Its performance was validated by fluorometrically monitoring the time-dependent changes in pH in E. coli biofilms after glucose inoculation at 37 °C and 4 °C. This revealed a temperature-dependent decrease in pH over a 4-h period caused by the acidifying glucose metabolism of E. coli. These studies demonstrate the applicability of this nanosensor to characterize the chemical microenvironment in biofilms with fluorescence methods.

Modular approach for theranostic polymer conjugates with activatable fluorescence: Impact of linker design on the stimuli-induced release of doxorubicin.

The introduction of cleavable motifs by dynamic covalent chemistry is widely applied in the design of drug delivery systems (DDS) to introduce controlled release properties. Since the cleavable moieties can be triggered by various exogenous or endogenous stimuli, the choice of the linker has substantial implications on the performance of the DDS. Here, we present a pair of theranostic polymer conjugates (TPC) to study the influence of the cleavable bond on the cell-mediated drug release by a facile in vitro fluorescence assay. The TPC represent model DDS that consist of dendritic polyglycerol as polymeric carrier labeled with an indodicarbocyanine (IDCC) dye and the chemotherapeutic drug doxorubicin (Dox) conjugated through different cleavable linkers. Cleavage of the conjugate can be mediated by either acidic environment or protease activity. The spatial proximity of the IDCC dye and the fluorescent drug led to effective quenching of Dox fluorescence when bound to the carrier. The stimuli-induced linker cleavage was correlated with the recovery of fluorescence giving real-time information about the stimuli-dependent drug release. By tracking the fluorescence recovery in a cell-based high throughput microplate assay, we were able to obtain characteristic release profiles of Dox for different cell lines. Here, we found that the pH-cleavable linker was more suitable for drug delivery applications since the enzyme-sensitive system suffered premature release due to the presence of extracellular proteases. This had a pronounced effect on the treatment of a multidrug-resistant cell line where an intracellular drug release is crucial to overcome the resistance mechanisms. We want to highlight that the modular synthetic approach combined with the cell-based assay has potential to extend the common in vitro methods to evaluate DDS performance and suitability as the design can be easily employed for diverse carrier/linker systems as well as various cell lines.

Acid-sensitive lipidated doxorubicin prodrug entrapped in nanoemulsion impairs lung tumor metastasis in a breast cancer model.

AIM: To develop an acid-sensitive lipidated, doxorubicin (Dox) prodrug (C16-Dox) to be entrapped in lipid nanoemulsion (NE-C16-Dox) as a nanocarrier to treat breast cancer models (in vitro and in vivo). RESULTS: We report the efficacy of NE-C16-Dox in in vitro experiments, as well as the improved chemotherapeutic index and tumor-control efficacy compared with treatment with free Dox in an in vivo murine 4T1 breast cancer model. In addition, NE-C16-Dox allowed the use of a higher dose of Dox, acceptable biocompatibility and a significant reduction in lung metastasis. CONCLUSION: Taken together, these results indicate that NE-C16-Dox is promising for breast cancer treatment, thus creating possibilities to translate these nanotechnology concepts to clinical applications.