The potential of dietary nanoparticles to enhance allergenicity of milk proteins: an in vitro investigation.

In recent years, the popularity of dietary nanoparticles (NPs) in the food industry as additives has raised concerns because of the lack of knowledge about potential adverse health outcomes ensuing from the interactions of NPs with components of the food matrix and gastrointestinal system. In this study, we used a transwell culture system that consisted of human colorectal adenocarcinoma (Caco-2) cells in the apical insert and Laboratory of Allergic Diseases 2 mast cells in the basal compartment to study the effect of NPs on milk allergen delivery across the epithelial layer, mast cell responses and signaling between epithelial and mast cells in allergenic inflammation. A library of dietary particles (silicon dioxide NPs, titanium dioxide NPs and silver NPs) that varied in particle size, surface chemistry and crystal structures with or without pre-exposure to milk was used in this investigation. Milk-interacted particles were found to acquire surface corona and increased the bioavailability of milk allergens (casein and ß-lactoglobulin) across the intestinal epithelial layer. The signaling between epithelial cells and mast cells resulted in significant changes in the early phase and late-phase activation of the mast cells. This study suggested that antigen challenge in mast cells with the presence of dietary NPs may cause the transition of allergic responses from an immunoglobulin E (IgE)-dependent mechanism to a mixed mechanism (both IgE-dependent and IgE-independent mechanisms).

Composite of Layered Double Hydroxide with Casein and Carboxymethylcellulose as a White Pigment for Food Application.

Titanium dioxide (TiO2) is commonly used in food, cosmetic, and pharmaceutical industries as a white pigment due to its extraordinary light scattering properties and high refractive index. However, as evidenced from recent reports, there are overriding concerns about the safety of nanoparticles of TiO2. As an alternative to TiO2, Mg-Al layered double hydroxide (LDH) and their composite containing casein and carboxymethyl cellulose (CMC) were synthesized using wet chemistry and compared with currently used materials (food grade TiO2 (E171), rice starch, and silicon dioxide (E551)) for its potential application as a white pigment. These particles were characterized for their size and shape (Transmission Electron Microscopy), crystallographic structure (X-Ray Diffraction), agglomeration behavior and surface charge (Dynamic Light Scattering), surface chemistry (Fourier Transform Infrared Spectroscopy), transmittance (UV-VIS spectroscopy), masking power, and cytotoxicity. Our results showed the formation of typical layered double hydroxide with flower-like morphology which was restructured into pseudo-spheres after casein intercalation. Transmittance measurement showed that LDH composites had better performance than pristine LDH, and the aqueous suspension was heat and pH resistant. While its masking power was not on a par with E171, the composite of LDH was superior to current alternatives such as rice starch and E551. Sustainability score obtained by MATLAB® based comparison for price, safety, and performance showed that LDH composite was better than any of the compared materials, highlighting its potential as a white pigment for applications in food.

Multimodal Imaging Probe Development for Pancreatic ß Cells: From Fluorescence to PET.

Pancreatic ß cells are responsible for insulin secretion and are important for glucose regulation in a healthy body and diabetic disease patient without prelabeling of islets. While the conventional biomarkers for diabetes have been glucose and insulin concentrations in the blood, the direct determination of the pancreatic ß cell mass would provide critical information for the disease status and progression. By combining fluorination and diversity-oriented fluorescence library strategy, we have developed a multimodal pancreatic ß cell probe PiF for both fluorescence and for PET (positron emission tomography). By simple tail vein injection, PiF stains pancreatic ß cells specifically and allows intraoperative fluorescent imaging of pancreatic islets. PiF-injected pancreatic tissue even facilitated an antibody-free islet analysis within 2 h, dramatically accelerating the day-long histological procedure without any fixing and dehydration step. Not only islets in the pancreas but also the low background of PiF in the liver allowed us to monitor the intraportal transplanted islets, which is the first in vivo visualization of transplanted human islets without a prelabeling of the islets. Finally, we could replace the built-in fluorine atom in PiF with radioactive 18F and successfully demonstrate in situ PET imaging for pancreatic islets.

Enhancing the Bioavailability of Silver Through Nanotechnology Approaches Could Overcome Efflux Pump Mediated Silver Resistance in Methicillin Resistant Staphylococcus aureus.

While the wide-spectrum antimicrobial properties and stability of silver nanomaterials have been copiously utilized in many medical and consumer products, we found that Methicillin Resistant Staphylococcus aureus (MRSA) is less susceptible to silver in comparison to Methicillin Sensitive Staphylococcus aureus (MSSA). Pre-exposure of MRSA to sub-lethal concentrations of AgNO3 caused 2.5-fold increase in LD50 of silver suggesting an inducible resistance mechanism. Studies involving gene expression profiling and efflux pump blockers showed the induction of P-type efflux pumps (Cop A, Cop Z and Nor B) as the principle mechanism conferring silver resistance in MRSA. Chlorpromazine-an efflux pump blocker increased sensitivity of MRSA to silver. Leveraging on these observations, silver resistance in MRSA was circumvented by enhancing the bioavailability of silver by cationic functioning of silver nanoparticles or by co-delivering silver together with chlorpromazine. Atomic Force Microscopy showed that poly-ethylene imine (PEI) functionalized silver nanoparticles adhere to bacterial cells which was found to increase the bioavailability, membrane rupture and cell death. The strategy of co-delivery of AgNO3 and chlorpromazine using chitosan-functionalized wormhole silica nanoparticles caused 12 log reduction in bacterial count which was 1000 times higher than bacterial reduction by AgNO3 alone. In short, these studies showed that circumventing antimicrobial resistance in pathogenic bacteria is possible by designed silver nanotechnology.

Two-Photon Dye Cocktail for Dual-Color 3D Imaging of Pancreatic Beta and Alpha Cells in Live Islets.

Insulin-secreting beta cells together with glucagon-producing alpha cells play an essential role in maintaining the optimal blood glucose level in the body, so the development of selective probes for imaging of these cell types in live islets is highly desired. Herein we report the development of a 2-glucosamine-based two-photon fluorescent probe, TP-ß, that is suitable for imaging of beta cells in live pancreatic islets from mice. Flow cytometry studies confirmed that TP-ß is suitable for isolation of primary beta cells. Moreover, two-photon imaging of TP-ß-stained pancreatic islets showed brightly stained beta cells in live islets. Insulin enzyme-linked immunosorbent assays revealed that TP-ß has no effect on glucose-stimulated insulin secretion from the stained islet. Finally, to develop a more convenient islet imaging application, we combined our recently published alpha-cell-selective probe TP-α with TP-ß to make a "TP islet cocktail". This unique dye cocktail enabled single excitation (820 nm) and simultaneous dual-color imaging of alpha cells (green) and beta cells (red) in live pancreatic islets. This robust TP islet cocktail may serve as a valuable tool for basic diabetic studies.

Glucagon-Secreting Alpha Cell Selective Two-Photon Fluorescent Probe TP-α: For Live Pancreatic Islet Imaging.

Two-photon (TP) microscopy has an advantage for live tissue imaging which allows a deeper tissue penetration up to 1 mm comparing to one-photon (OP) microscopy. While there are several OP fluorescence probes in use for pancreatic islet imaging, TP imaging of selective cells in live islet still remains a challenge. Herein, we report the discovery of first TP live pancreatic islet imaging probe; TP-α (Two Photon-alpha) which can selectively stain glucagon secreting alpha cells. Through fluorescent image based screening using three pancreatic cell lines, we discovered TP-α from a TP fluorescent dye library TPG (TP-Green). In vitro fluorescence test showed that TP-α have direct interaction and appear glucagon with a significant fluorescence increase, but not with insulin or other hormones/analytes. Finally, TP-α was successfully applied for 3D imaging of live islets by staining alpha cell directly. The newly developed TP-α can be a practical tool to evaluate and identify live alpha cells in terms of localization, distribution and availability in the intact islets.