Monika Köll-Weber

Prophylaxis and the treatment of surgical site infections (SSIs) with antibiotics frequently fail due to the antibiotic resistance of bacteria and the ability of bacteria to reside in biofilms (i.e., bacterial clusters in a protective matrix). Therefore, alternative antibacterial treatments are required to combat biofilm infections. The combination of diethyldithiocarbamate (DDC⁻) and copper ions (Cu²⁺) exhibited antibiofilm activity against the staphylococci species associated with SSIs; however, the formation of a water-insoluble Cu(DDC)₂ complex limits its application to SSIs. Here, we describe the development and antibiofilm activity of an injectable gel containing a liposomal formulation of Cu(DDC)₂ and Cu²⁺ (lipogel). Lyophilized liposomes were incorporated into a mixture of chitosan (CS) and beta-glycerophosphate (βGP), and the thermosensitive gelling properties of CS-βGP and the lipogel were determined. The liposomes remained stable after lyophilization over six months at 4–6 °C and −20 °C. The sol-gel transition of the gel and lipogel occurred between 33 and 39 °C, independently of sterilization or storage at −20 °C. CS-βGP is biocompatible and the liposomes were released over time. The lipogel prevented biofilm formation over 2 days and killed 98.7% of the methicillin-resistant Staphylococcus aureus and 99.9% of the Staphylococcus epidermidis biofilms. Therefore, the lipogel is a promising new prophylaxis and treatment strategy for local application to SSIs.

Adrenocortical carcinoma (ACC) is a heterogeneous malignancy related to poor prognosis and limited treatment options. The orphan drug mitotane (MT) is still a cornerstone in ACC therapy, however, its application is characterized by low aqueous solubility, poor bioavailability, and unfavorable pharmacokinetics, often resulting in below-target plasma concentrations or toxic side effects. Throughout the last decades, nanoparticulate formulations have become attractive carriers to improve anticancer therapy. In this study, injectable MT liposomes (DOPC-MT) and albumin-stabilized MT nanoparticles (BSA-MT) were investigated in depth with respect to their physicochemical properties, and their colloidal and therapeutical stability upon storage. Furthermore, in vitro cytotoxicity was evaluated using the ACC model cell line NCI-H295R for preparing multicellular tumor spheroids, and was compared to non-malignant human dermal fibroblasts. Our results clearly demonstrate that BSA-MT, unlike DOPC-MT, represents a stable and storable MT formulation with a high drug concentration in an aqueous medium. Dual centrifugation was established as a reproducible method for nanoparticle preparation. Although an efficient cytotoxic effect on ACC tumor spheroids was demonstrated, concomitant low toxicity to fibroblasts suggests that higher drug concentrations may be tolerated in vivo. Consequently, BSA-MT is a novel and promising therapeutical approach to address key challenges in MT treatment.

Preclinical in vitro studies of drug candidates for anticancer therapy are generally conducted on well-established 2D cell models. Unfortunately, these models are unable to mimic the properties of in vivo tumors. However, in vitro 3D models (spheroids) have been proven to be superior in reflecting the tumor microenvironment. Diethyldithiocarbamate (DDC⁻) is the active metabolite of Disulfiram, an approved drug for alcoholism and repurposed for cancer treatment. DDC⁻ binds copper in a molar ratio of 2:1 resulting in a water-insoluble Cu(DDC)₂ complex exhibiting anticancer activities. Delivery of the Cu(DDC)₂ complex using nanoparticulate carriers provides decisive advantages for a parental application. In this study, an injectable liposomal Cu(DDC)₂ formulation was developed and the toxicity was compared with a 2D neuroblastoma and a 3D neuroblastoma cell model. Our results indicate that Cu(DDC)₂ liposomes complied with the size requirements of nanoparticles for intravenous injection and demonstrated high drug to lipid ratios as well as colloidal stability upon storage. Furthermore, an efficient cytotoxic effect on neuroblastoma 2D cell cultures and a very promising and even more pronounced effect on 3D cell cultures in terms of neuroblastoma monoculture and neuroblastoma co-culture with primary cell lines was proven, highly encouraging the use of Cu(DDC)₂ liposomes for anticancer therapy.