Nano-mupirocin as tumor-targeted antibiotic: Physicochemical, immunotoxicological and pharmacokinetic characterization, and effect on gut microbiome.

Nano-mupirocin is a PEGylated nano-liposomal formulation of the antibiotic mupirocin, undergoing evaluation for treating infectious diseases and intratumor bacteria. Intratumoral microbiota play an important role in the regulation of tumor progression and therapeutic efficacy. However, antibiotic use to target intratumoral bacteria should be performed in a way that will not affect the gut microbiota, found to enable the efficacy of cancer treatments. Nano-mupirocin may offer such a selective treatment. Herein, we demonstrate the ability of Nano-mupirocin to successfully target tumor-residing Fusobacterium nucleatum without an immediate effect on the gut microbiome. In-depth characterization of this novel formulation was performed, and the main findings include: (i). the pharmacokinetic analysis of mupirocin administered as Nano-mupirocin vs mupirocin lithium (free drug) demonstrated that most of the Nano-mupirocin in plasma is liposome associated; (ii). microbiome analysis of rat feces showed no significant short-term difference between Nano-mupirocin, mupirocin lithium and controls; (iii). Nano-mupirocin was active against intratumoral F. nucleatum, a tumor promoting bacteria that accumulates in tumors of the AT3 mice model of breast cancer. These data suggest the ability of Nano-mupirocin to target tumor residing and promoting bacteria.

Advancements in Nanoparticle Characterization.

Nanotechnology for drug delivery has made significant advancements over the last two decades. Innovations have been made in cancer research and development, including chemotherapies, imaging agents, and vaccine strategies, as well as other therapeutic areas, e.g., the recent commercialization of mRNA lipid nanoparticles as vaccines against the SARS-CoV-2 virus. The field has also seen technological advancements to aid in addressing the complex questions posed by these novel therapies. In this latest edition of protocols and methods for nanoparticle characterization, we highlight both old and new methodologies for defining physicochemical properties, present both in vitro and in vivo methods to test for a variety of immunotoxicities, and describe assays used for pharmacological studies to assess drug release and tissue distribution.

Assessment of Temperature-Dependent Drug Release of Solubilizing Nanoformulations Using the SITUA.

The evaluation of temperature-dependent drug release for solubilizing nanoformulations uses a modification of the stable isotope ultrafiltration assay (SITUA). This method is specific to parenterally administered solubilizing nanomedicines and can be used to assess drug release from the total dosage form for regulatory purposes of lot release. The principle upon which this method is based is the relationship between drug solubility and temperature in a plasma simulating media, 4.5% human serum albumin, that allows for discrimination of passing and failing lots based upon the release characteristics.

Evaluation of Nanomedicine Tissue Distribution and Stability by Alexa Fluor 488 and PEG Immunohistochemistry.

A primary issue with nanomedicine biological evaluation is determination of nanoparticle carrier tissue distribution and stability. Here we present a method to evaluate nanomedicine distribution in tissues that is applicable to most nanomedicine constructs. This method utilizes immunohistochemical (IHC) analysis of an Alexa Fluor 488-tag and/or polyethylene glycol (PEG), a very common nanomedicine component, for tissue localization. Using specific Alexa Fluor 488- and/or PEG antibody-based IHC staining procedures allows evaluation of high-resolution nanoparticle tissue distribution, nanoparticle tissue stability, and also allows correlation of distribution with morphological changes. This protocol outlines the methods to follow to ensure proper tissue collection and optimized immunohistochemical staining of Alexa Fluor 488-tag and PEG in tissues.