Integrating microneedles and sensing strategies for diagnostic and monitoring applications: The state of the art.

Microneedles (MNs) offer minimally-invasive access to interstitial fluid (ISF) - a potent alternative to blood in terms of monitoring physiological analytes. This property is particularly advantageous for the painless detection and monitoring of drugs and biomolecules. However, the complexity of the skin environment, coupled with the inherent nature of the analytes being detected and the inherent physical properties of MNs, pose challenges when conducting physiological monitoring using this fluid. In this review, we discuss different sensing mechanisms and highlight advancements in monitoring different targets, with a particular focus on drug monitoring. We further list the current challenges facing the field and conclude by discussing aspects of MN design which serve to enhance their performance when monitoring different classes of analytes.

Therapeutic applications of nanoparticles targeting neutrophil and extracellular traps.

Neutrophils, the most abundant leukocytes in human circulation, are key effectors and regulators of both innate and adaptive immunity which migrate from the bloodstream to sites of inflammation or infection in response to different stimuli. A growing body of evidence has revealed that dysregulated neutrophil activity contributes to the development of several diseases. Targeting their function has been proposed as a potential strategy to treat or mitigate the progression of these disorders. Additionally, neutrophil tropism has been proposed as a strategy to drive therapeutic agents towards targeted disease sites. In this article, we review the proposed nanomedicine approaches to target neutrophils and their components, the regulation of their function and the use of their tropism in drug delivery for therapeutic purposes.

Current knowledge on the tissue distribution of mRNA nanocarriers for therapeutic protein expression.

Exogenously delivered mRNA-based drugs are emerging as a new class of therapeutics with the potential to treat several diseases. Over the last decade, advancements in the design of non-viral delivery tools have enabled mRNA to be evaluated for several therapeutic purposes including protein replacement therapies, gene editing, and vaccines. However, in vivo delivery of mRNA to targeted organs and cells remains a critical challenge. Evaluation of the biodistribution of mRNA vehicles is of utmost importance for the development of effective pharmaceutical candidates. In this review, we discuss the recent advances in the design of nanoparticles loaded with mRNA and extrapolate the key factors influencing their biodistribution following administration. Finally, we highlight the latest developments in the preclinical and clinical translation of mRNA therapeutics for protein supplementation therapy.

Optimization of a Liposomal DNase I Formulation with an Extended Circulating Half-Life.

Drug delivery systems such as liposomes are widely used to stabilize and increase the plasma half-life of therapeutics. In this article, we have investigated two strategies to increase the half-life of deoxyribonuclease I, an FDA-approved enzyme used for the treatment of cystic fibrosis, and a potential candidate for the reduction of uncontrolled inflammation induced by neutrophil extracellular traps. We demonstrate that our optimized preparation procedure resulted in nanoparticles with improved plasma half-life and total exposure relative to native protein, while maintaining enzymatic activity.

Development of a diffusion-weighed mathematical model for intradermal drainage quantification.

The quantitative assessment of lymphatic dermal clearance using NIR fluorescent tracers is particularly important for the early diagnosis of several potential disabling diseases. Currently, half-life values are computed using a mono-exponential mathematical model, neglecting diffusion of the tracer within the dermis after injection. The size and position of the region of interest are subjectively manually selected around the point of injection on the skin surface where the fluorescence signal intensity is averaged, neglecting any spatial information contained in the image. In this study we present and test a novel mathematical model allowing the objective quantification of dermal clearance, taking into consideration potential dermal diffusion. With only two parameters, this "clearance-diffusion" model is simple enough to be applied in a variety of settings and requires almost no prior information about the system. We demonstrate that if dermal diffusion is low, the mono-exponential approach is suitable but still lacking objectivity. However, if dermal diffusion is substantial, the clearance-diffusion model is superior and allows the accurate calculation of half-life values.

A Naked Eye-Invisible Ratiometric Fluorescent Microneedle Tattoo for Real-Time Monitoring of Inflammatory Skin Conditions.

The field of portable healthcare monitoring devices has an urgent need for the development of real-time, noninvasive sensing and detection methods for various physiological analytes. Currently, transdermal sensing techniques are severely limited in scope (i.e., measurement of heart rate or sweat composition), or else tend to be invasive, often needing to be performed in a clinical setting. This study proposes a minimally invasive alternative strategy, consisting of using dissolving polymeric microneedles to deliver naked eye-invisible functional fluorescent ratiometric microneedle tattoos directly to the skin for real-time monitoring and quantification of physiological and pathological parameters. Reactive oxygen species are overexpressed in the skin in association with various pathological conditions. Here, one demonstrates for the first time the microneedle-based delivery to the skin of active fluorescent sensors in the form of an invisible, ratiometric microneedle tattoo capable of sensing reactive oxygen species in a reconstructed human-based skin disease model, as well as an in vivo model of UV-induced dermal inflammation. One also elaborates a universal ratiometric quantification concept coupled with a custom-built, multiwavelength portable fluorescence detection system. Fully realized, this approach presents an opportunity for the minimally invasive monitoring of a broad range of physiological parameters through the skin.

Data on the removal of peroxides from functionalized polyethylene glycol (PEG) and effects on the stability and sensitivity of resulting PEGylated conjugates.

Cyanine-5 (Cy5) is a fluorescent dye active in the far-red region of the visible spectrum (λex = 646 nm, λem = 662 nm) [1]. While Cy5 displays fluorescence in its oxidized form, it can be readily converted to its non-fluorescent hydrocyanine equivalent (H-Cy5) when exposed to reducing agents. H-Cy5 can then be converted back to its fluorescent oxidized form when exposed to reactive oxygen species (ROS), allowing it to act as a highly sensitive, high wavelength fluorescent ROS sensor [2]. However, H-Cy5 is a small, poorly water-soluble molecule, and is rapidly taken up into cells in vivo, preventing its use for sensing extracellular ROS, which are implicated in inflammation, wound healing, and other processes [3], [4], [5], [6]. A solution to this lies in the conjugation of Cy5 to a polyethylene glycol (PEG) polymer, increasing its solubility [7]. This conjugate (Cy5-PEG) can be reduced to H-Cy5-PEG to allow the highly sensitive detection of ROS in an aqueous extracellular environment. However, after PEG conjugation, a significant decrease in stability and sensitivity is observed, likely owing to the presence of ROS contaminants in commercial samples of PEG. It has been reported that these ROS impurities can be removed from PEG through a simple freeze-drying procedure [8]. Here, we demonstrate that a simple, straightforward method for the purification of PEG can allow the synthesis of a highly functional, water-soluble ROS sensor that could be used for extracellular ROS sensing.

Rational design of a fluorescent microneedle tattoo for minimally invasive monitoring of lymphatic function.

The monitoring of lymphatic drainage is of great importance, particularly in the context of the early detection and diagnosis of several diseases. Existing methods of imaging and monitoring lymphatic drainage can be costly and require trained personnel, posing problems for at-home or point-of-care monitoring. Recently, an alternative approach has been proposed, consisting of using microneedles to deliver a near-infrared (NIR) fluorescent tattoo to the skin, which can be monitored with traditional laboratory-based fluorescence detectors. In this work, we present further development of this approach, using a specifically designed NIR-fluorescent probe and rational optimization of microneedle properties and the spatial location of the NIR dye within the microneedles. Moreover, we demonstrate that this method is compatible with a custom-made portable fluorescence measurement device and able to discriminate between drainage and lack of drainage in vivo in rats.

A Snapshot of Transdermal and Topical Drug Delivery Research in Canada.

The minimally- or non-invasive delivery of therapeutic agents through the skin has several advantages compared to other delivery routes and plays an important role in medical care routines. The development and refinement of new technologies is leading to a drastic expansion of the arsenal of drugs that can benefit from this delivery strategy and is further intensifying its impact in medicine. Within Canada, as well, a few research groups have worked on the development of state-of-the-art transdermal delivery technologies. Within this short review, we aim to provide a critical overview of the development of these technologies in the Canadian environment.

Advances in the Design of Transdermal Microneedles for Diagnostic and Monitoring Applications.

Due to their intrinsic advantages over classical hypodermic needles, microneedles have received much attention over the last two decades and will likely soon appear in clinics. Although the vast majority of research is focused on designing microneedles for the painless delivery of drugs, their applications for diagnostic purposes have also provided promising results. In this paper, the main advances in the field of microneedles for diagnostic and patient monitoring purposes are introduced and critically discussed.

Poly(2-oxazoline)-Pterostilbene Block Copolymer Nanoparticles for Dual-Anticancer Drug Delivery.

Functional block copolymers based on poly(2-oxazoline)s are versatile building blocks for the fabrication of dual-drug delivery nanoparticles (NPs) for anticancer chemotherapy. Core-shell NPs are fabricated from diblock copolymers featuring a long and hydrophilic poly(2-methyl-2-oxazoline) (PMOXA) block coupled to a relatively short and functionalizable poly(2-methylsuccinate-2-oxazoline) (PMestOXA) segment. The PMOXA block stabilizes the NP dispersions, whereas the PMestOXA segment is used to conjugate pterostilbene, a natural bioactive phenolic compound that is used as lipophilic model-drug and constitutes the hydrophobic core of the designed NPs. Subsequent loading of the NPs with clofazimine (CFZ), an inhibitor of the multidrug resistance pumps typically expressed in a large variety of cancer cells, provides an additional function to their formulation. Optimization of the copolymer composition allows the design of polymer scaffolds showing low toxicity and capable of assembling into highly stable NPs dispersions at physiologically relevant pH. In addition, the incorporation of CFZ increases the stability of the NPs and stimulates their internalization by RAW 264.7 cells.