Preparation and evaluation of effect on Escherichia coli and Staphylococcus aureus of radiolabeled ampicillin-loaded graphene oxide nanoflakes

In vitro evaluation of 99m Tc-sultamicillin for infection imaging

Early detection of the site of infection non-invasively with radiolabeled molecules is important for the success of treatment. Technetium-99m labeled antibiotics have the potential to discriminate between bacterial infection and sterile inflammation. Sultamicillin is the tosylate salt of the double ester of sulbactam plus ampicillin. In this study, sultamicillin was labeled with ^99m Tc according to the stannous chloride method. Quality control studies of radiolabeled sultamicillin were performed by radiochromatographic methods. In vitro binding assays were performed in live and heat-killed gram-positive Staphylococcus aureus and gram-negative Escherichia coli strains. The radiolabeling yield of ^99m Tc-sultamicillin was determined as 97.8% ± 3.1% (n = 5). The maximum bacterial uptake of ^99m Tc-sultamicillin was 80.7% ± 11.00% at 4 h for living S. aureus and 93.2% ± 4.40% at 2 h for E. coli. Bacterial uptake study results show that sultamicillin has the potential to be a nuclear imaging agent, especially in infections caused by gram-negative E. coli and gram-positive S. aureus.

Advances in Drug Delivery Nanosystems Using Graphene-Based Materials and Carbon Nanotubes

Carbon is one of the most abundant elements on Earth. In addition to the well-known crystallographic modifications such as graphite and diamond, other allotropic carbon modifications such as graphene-based nanomaterials and carbon nanotubes have recently come to the fore. These carbon nanomaterials can be designed to help deliver or target drugs more efficiently and to innovate therapeutic approaches, especially for cancer treatment, but also for the development of new diagnostic agents for malignancies and are expected to help combine molecular imaging for diagnosis with therapies. This paper summarizes the latest designed drug delivery nanosystems based on graphene, graphene quantum dots, graphene oxide, reduced graphene oxide and carbon nanotubes, mainly for anticancer therapy.

Radiolabelling of nanomaterials for medical imaging and therapy

Nanomaterials offer unique physical, chemical and biological properties of interest for medical imaging and therapy. Over the last two decades, there has been an increasing effort to translate nanomaterial-based medicinal products (so-called nanomedicines) into clinical practice and, although multiple nanoparticle-based formulations are clinically available, there is still a disparity between the number of pre-clinical products and those that reach clinical approval. To facilitate the efficient clinical translation of nanomedicinal-drugs, it is important to study their whole-body biodistribution and pharmacokinetics from the early stages of their development. Integrating this knowledge with that of their therapeutic profile and/or toxicity should provide a powerful combination to efficiently inform nanomedicine trials and allow early selection of the most promising candidates. In this context, radiolabelling nanomaterials allows whole-body and non-invasive in vivo tracking by the sensitive clinical imaging techniques positron emission tomography (PET), and single photon emission computed tomography (SPECT). Furthermore, certain radionuclides with specific nuclear emissions can elicit therapeutic effects by themselves, leading to radionuclide-based therapy. To ensure robust information during the development of nanomaterials for PET/SPECT imaging and/or radionuclide therapy, selection of the most appropriate radiolabelling method and knowledge of its limitations are critical. Different radiolabelling strategies are available depending on the type of material, the radionuclide and/or the final application. In this review we describe the different radiolabelling strategies currently available, with a critical vision over their advantages and disadvantages. The final aim is to review the most relevant and up-to-date knowledge available in this field, and support the efficient clinical translation of future nanomedicinal products for in vivo imaging and/or therapy.

Evaluation of 99mTechnetium-Vancomycin Imaging Potential in Experimental Rat Model for the Diagnosis of Infective Endocarditis

BACKGROUND

Infective endocarditis (IE) is an infection of the heart's endocardial surface. In recent years, nuclear imaging methods have gained importance in the diagnosis of IE. The present study aims to investigate the imaging potential of ^99mTc-labeled vancomycin (^99mTc-Vancomycin) as a new agent that would enable the diagnosis of IE in its early stages when it is difficult to diagnose or has small vegetation in the experimental rat model.

METHODS

^99mTc-Vancomycin scintigraphy was evaluated for its accumulation in IE with Staphylococcus aureus performed in an experimental rat model. Serial planar scintigraphic and biodistribution analysis of infected vegetations are compared to rats with sterile vegetations. The heart was identified as an infected organ, the liver was identified as a non-infected organ and the heart/liver uptake ratio (T / NT ratio) was compared between infective endocarditis and sterile endocarditis groups.

RESULTS

Planar scintigrams (in vivo measurements) showed more uptake in the heart of rats in the infective endocarditis group compared to the uptake in the heart of rats in the sterile endocarditis group, but this difference was not statistically significant (p>0.05). From the ex vivo measurements, the ^99mTc-Vancomycin heart uptake increased significantly (p = 0.016), liver uptake was significantly decreased (p = 0.045) and the T/NT ratio was significantly higher (p = 0.014) in the infective endocarditis group compared to the sterile endocarditis group.

CONCLUSION

In this experimental study, ^99mTc-Vancomycin scintigraphy ensured the detection of ex vivo infected tissue in a rat model of IE. In addition, the absence of significant ^99mTc-Vancomycin uptake in the sterile endocarditis group indicates that this agent targeted the infected tissue instead of the sterile inflammatory tissue. Finally, this agent should also be evaluated with animal- specific imaging devices.

Anti-pathogenic activity of graphene nanomaterials: A review

Graphene and its derivatives are promising candidates for a variety of biological applications, among which, their anti-pathogenic properties are highly attractive due to the outstanding physicochemical characteristics of these novel nanomaterials. The antibacterial, antiviral and antifungal performances of graphene are increasingly becoming more important due to the pathogen's resistance to existing drugs. Despite this, the factors influencing the antibacterial activity of graphene nanomaterials, and consequently, the mechanisms involved are still controversial. This review aims to systematically summarize the literature, discussing various factors that affect the antibacterial performance of graphene materials, including the shape, size, functional group and the electrical conductivity of graphene flakes, as well as the concentration, contact time and the pH value of the graphene suspensions used in related microbial tests. We discuss the possible surface and edge interactions between bacterial cells and graphene nanomaterials, which cause antibacterial effects such as membrane/oxidative/photothermal stresses, charge transfer, entrapment and self-killing phenomena. This article reviews the anti-pathogenic activity of graphene nanomaterials, comprising their antibacterial, antiviral, antifungal and biofilm-forming performance, with an emphasis on the antibacterial mechanisms involved.