Photodynamic therapy (PDT) is a promising treatment strategy where activation of photosensitizer drugs with specific wavelengths of light results in energy transfer cascades that ultimately yield cytotoxic reactive oxygen species which can render apoptotic and necrotic cell death. Without light the photosensitizer drugs are minimally toxic and the photoactivating light itself is non-ionizing. Therefore, harnessing this mechanism in tumors provides a safe and novel way to selectively eradicate tumor with reduced systemic toxicity and side effects on healthy tissues. For successful PDT of solid tumors, it is necessary to ensure tumor-selective delivery of the photosensitizers, as well as, the photoactivating light and to establish dosimetric correlation of light and drug parameters to PDT-induced tumor response. To this end, the nanomedicine approach provides a promising way towards enhanced control of photosensitizer biodistribution and tumor-selective delivery. In addition, refinement of nanoparticle designs can also allow incorporation of imaging agents, light delivery components and dosimetric components. This review aims at describing the current state-of-the-art regarding nanomedicine strategies in PDT, with a comprehensive narrative of the research that has been carried out in vitro and in vivo, with a discussion of the nanoformulation design aspects and a perspective on the promise and challenges of PDT regarding successful translation into clinical application.

Lactobacillus reuteri 100-23 is a bacterial commensal of the gastrointestinal tract of mice. Previous studies have shown that colonization of the murine gut by this strain stimulates small-bowel enterocytes to produce proinflammatory cytokines. This is associated with a mild, transitory inflammatory response 6 days after inoculation of formerly Lactobacillus-free animals. The inflammation subsides by 21 days after colonization, although lactobacilli continue to be present in the bowel. To determine the immunological mechanisms that underpin tolerance to bowel commensals, we investigated cytokine responses of dendritic cells The digestive tracts of mammals contain biodiverse bacterial communities, the members of which are referred to as commensals. 1 The forestomach of the gastric region of mice is lined with a keratinized, stratified squamous epithelium, and commensal lactobacilli, such as Lactobacillus reuteri strain 100-23, attach directly to this epithelium. They proliferate to form a layer (biofilm) of cells, and as they are carried on squames into the digesta, they can be detected in substantial numbers throughout the remainder of the digestive tract. 2 A unique mouse colony has been developed, which, unlike conventional mice, does not harbor lactobacilli as commensals of the digestive tract. 3 Although Lactobacillus free, the mice harbor a biodiverse bacterial community in the large bowel. The mucosa is therefore conditioned by exposure to bacteria, characteristic of the murine bowel biome, but is naive with respect to the influences of lactobacilli. These mice provide a defined system by which the impact of lactobacilli on the host immune response can be studied.Oral administration of L. reuteri 100-23 cells to adult Lactobacillusfree mice results in colonization of the forestomach by lactobacilli and a mild inflammatory response in the ileal mucosa 6 days after inoculation. 4 Transcription of genes encoding interleukin (IL)-1a and IL-6 is increased in small-bowel enterocytes at this time. This coincides with the development of a maximal population of lactobacilli in the ileum. Although the numbers of lactobacilli remain at this same constant level throughout the remainder of the animal's life, inflammation is transient and resolves by 21 days after inoculation, at which time the IL gene expression of enterocytes returns to baseline. 4 It seems, therefore, that the innate immune response to the presence of L. reuteri 100-23 is downregulated with time, but by an as yet unknown mechanism. Antibodies that react with a large protein on the surface of L. reuteri 100-23 cells, indicative of an adaptive immune response, are present in sera of mice that have been colonized by the bacteria, but not in the sera of noncolonized mice (GW Tannock, unpublished). Overall, however, bowel commensals do not invoke an immune response of pathological consequences under normal circumstances. The mechanisms by which this is achieved are largely unknown. Thus, we used the L. reuteri 100-23/Lactobacillus-free mouse paradigm to...

Lactobacillus reuteri strain 100-23 together with a Lactobacillus-free mouse model, provides a system with which the molecular traits underpinning bacterial commensalism in vertebrates can be studied. A polysaccharide was extracted from sucrose-containing liquid cultures of strain 100-23. Chemical analysis showed that this exopolysaccharide was a levan (b-2, 6-linked fructan). Mutation of the fructosyl transferase (ftf) gene resulted in loss of exopolysaccharide production. The ftf mutant was able to colonise the murine gastrointestinal tract in the absence of competition, but colonisation was impaired in competition with the wild type. Biofilm formation by the mutant on the forestomach epithelial surface was not impaired and the matrix between cells was indistinguishable from that of the wild type in electron micrographs. Colonisation of the mouse gut by the wild-type strain led to increased proportions of regulatory T cells (Foxp3 þ ) in the spleen, whereas colonisation by the ftf mutant did not. Survival of the mutant in sucrose-containing medium was markedly reduced relative to the wild type. Comparison of the genomic ftf loci of strain 100-23 with other L. reuteri strains suggested that the ftf gene was acquired by lateral gene transfer early in the evolution of the species and subsequently diversified at accelerated rates. Levan production by L. reuteri 100-23 may represent a function acquired by the bacterial species for life in moderate to high-sucrose extra-gastrointestinal environments that has subsequently been diverted to novel uses, including immunomodulation, that aid in colonisation of the murine gut.

Personalized cancer therapy focuses on characterizing the relevant phenotypes of the patient, as well as the patient’s tumor, to predict the most effective cancer therapy. Historically, these methods have not proven predictive in regards to predicting therapeutic response. Emerging culture platforms are designed to better recapitulate the in vivo environment, thus, there is renewed interest in integrating patient samples into in vitro cancer models to assess therapeutic response. Successful examples of translating in vitro response to clinical relevance are limited due to issues with patient sample acquisition, variability and culture. We will review traditional and emerging in vitro models for personalized medicine, focusing on the technologies, microenvironmental components, and readouts utilized. We will then offer our perspective on how to apply a framework derived from toxicology and ecology towards designing improved personalized in vitro models of cancer. The framework serves as a tool for identifying optimal readouts and culture conditions, thus maximizing the information gained from each patient sample.

The current clinical mainstays for cancer treatment, namely, surgical resection, chemotherapy and radiotherapy, can cause significant trauma, systemic toxicity, and functional/cosmetic debilitation of tissue, especially if repetitive treatment becomes necessary due to tumor recurrence. Hence there is significant clinical interest in alternate treatment strategies like photodynamic therapy (PDT) which can effectively and selectively eradicate tumors and can be safely repeated if needed. We have previously demonstrated that the second-generation photosensitizer Pc 4 can be formulated within polymeric micelles, and these micelles can be specifically targeted to EGFR-overexpressing cancer cells using GE11 peptide ligands, to enhance cell-specific Pc 4 delivery and internalization. In the current study, we report on the in vitro optimization of the EGFR-targeting, Pc 4 loading of the micellar nanoformulation, along with optimization of the corresponding photoirradiation conditions to maximize Pc 4 delivery, internalization and subsequent PDT-induced cytotoxicity in EGFR-overexpressing cells in vitro. In our studies, absorption and fluorescence spectroscopy were used to monitor the cell-specific uptake of the GE11-decorated Pc 4-loaded micelles and the cytotoxic singlet oxygen production from the micelle-encapsulated Pc 4, to determine the optimum ligand density and Pc 4 loading. It was found that the micelle formulations bearing 10 mole% of GE11-modified polymer component resulted in the highest cellular uptake in EGFR-overexpressing A431 cells within the shortest incubation periods. Also, the loading of ~50 μg Pc 4 per mg of polymer in these micellar formulations resulted in the highest levels of singlet oxygen production. When formulations bearing these optimized parameters were tested in vitro on A431 cells for PDT effect, a formulation dose containing 400 nM Pc 4 and photoirradiation duration of 400 seconds at a fluence of 200 mJ/cm2 yielded close to 100% cell death.

Microfluidic lumen-based systems are microscale models that recapitulate the anatomy and physiology of tubular organs. Here, we review recent microfluidic lumen-based systems and their applications in basic and translational biomedical research.

The estrogen receptor (ER) regulates the survival and growth of breast cancer cells, but it is less clear how components of the tissue microenvironment affect ER-mediated responses. We set out to test how human mammary fibroblasts (HMFs) modulate ER signaling and downstream cellular responses. We exposed an organotypic mammary model consisting of a collagen-embedded duct structure lined with MCF7 cells to 17-β estradiol (E2), with and without HMFs in the surrounding matrix. MCF7 cells grown as ductal structures were polarized and proliferated at rates comparable to in vivo breast tissue. In both culture platforms, exposure to E2 increased ER transactivation, increased proliferation, and induced ductal hyperplasia. When the surrounding matrix contained HMFs, the onset and severity of E2-induced ductal hyperplasia was increased due to decreased apoptosis. The reduced apoptosis may be due to fibroblasts modulating ER signaling in MCF7 cells, as suggested by the increased ER transactivation and reduced ER protein in MCF7 cells grown in co-culture. These findings demonstrate the utility of organotypic platforms when studying stromal:epithelial interactions, and add to existing literature that implicate the mammary microenvironment in ER + breast cancer progression.

The tumour microenvironment (TME) has recently drawn much attention due to its profound impact on tumour development, drug resistance and patient outcome. There is an increasing interest in new therapies that target the TME. Nonetheless, most established in vitro models fail to include essential cues of the TME. Microfluidics can be used to reproduce the TME in vitro and hence provide valuable insight on tumour evolution and drug sensitivity. However, microfluidics remains far from well-established mainstream molecular and cell biology methods. Therefore, we have developed a quick and straightforward collagenase-based enzymatic method to recover cells embedded in a 3D hydrogel in a microfluidic device with no impact on cell viability. We demonstrate the validity of this method on two different cell lines in a TME microfluidic model. Cells were successfully retrieved with high viability, and we characterised the different cell death mechanisms via AMNIS image cytometry in our model.