Activatable cell penetrating peptide-peptide nucleic acid conjugate via reduction of azobenzene PEG chains

The use of stimuli-responsive bioactive molecules is an attractive strategy to circumvent selectivity issues in vivo. Here, we report an activatable cell penetrating peptide (CPP) strategy ultimately aimed at delivering nucleic acid drugs to the colon mucosa using bacterial azoreductase as the local reconversion trigger. Through screening of a panel of CPPs, we identified a sequence (M918) capable of carrying a nucleic acid analogue payload. A modified M918 peptide conjugated to a peptide nucleic acid (PNA) was shown to silence luciferase in colon adenocarcinoma cells (HT-29-luc). Reversible functionalization of the conjugate's lysine residues via an azobenzene self-immolative linkage abolished transfection activity, and the free CPP-PNA was recovered after reduction of the azobenzene bond. This activatable CPP conjugate platform could find applications in the selective delivery of nucleic acid drugs to the colon mucosa, opening therapeutic avenues in colon diseases.

Plasmonic biocompatible silver–gold alloyed nanoparticles

Nanoalloying Ag with Au minimizes nanoparticle surface oxidation and subsequent toxic Ag⁺ ion release rendering such nanoparticles safer for theranostic applications.

MR imaging of therapeutic magnetic microcarriers guided by magnetic resonance navigation for targeted liver chemoembolization

PURPOSE

Magnetic resonance navigation (MRN), achieved with an upgraded MRI scanner, aims to guide new therapeutic magnetic microcarriers (TMMC) from their release in the hepatic vascular network to liver tumor. In this technical note, in vitro and in vivo MRI properties of TMMC, loaded with iron-cobalt nanoparticles and doxorubicin, are reported by following three objectives: (1) to evaluate the lengthening of echo-time (TE) on nano/microparticle imaging; (2) to characterize by MRI TMMC distribution in the liver; and (3) to confirm the feasibility of monitoring particle distribution in real time.

METHODS

Phantom studies were conducted to analyze nano/microparticle signals on T 2*-weighted gradient-echo (GRE) MR images according to sample weight and TE. Twelve animal experiments were used to determine in vivo MRI parameters. TMMC tracking was evaluated by magnetic resonance imaging (MRI) in four rabbits, which underwent MRN in the hepatic artery, three without steering, two in real-time, and three as blank controls. TMMC distribution in the right and left liver lobes, determined by ex vivo MR image analysis, was compared to the one obtained by cobalt level analysis.

RESULTS

TMMC induced a hypointense signal that overran the physical size of the sample on MR images. This signal, due to the nanoparticles embedded into the microparticles, increased significantly with echo-time and sample amount (p < 0.05). In vivo, without steering, contrast-to-noise ratio (CNR) values for the right and left lobes were similar. With MRN, the CNR in the targeted lobe was different from that in the untargeted lobe (p = 0.003). Ex vivo, TMMC distribution, based on MRI signal loss volume measurement, was correlated with that quantified by Co level analysis (r = 0.92). TMMC accumulation was tracked in real time with an 8-s GRE sequence.

CONCLUSIONS

MRI signal loss induced by TMMC can serve to track particle accumulation and to assess MRN efficiency.

Improving the stability and activity of oral therapeutic enzymes-recent advances and perspectives

Exogenous, orally-administered enzymes are currently in clinical use or under development for the treatment of pathologies, such as celiac disease and phenylketonuria. However, the administration of therapeutic enzymes via the oral route remains challenging due to potential inactivation of these fragile macromolecular entities in the harsh environment of the gastrointestinal tract. Enzymes are particularly sensitive because both proteolysis and unfolding can lead to their inactivation. Current efforts to overcome these shortcomings involve the application of gastro-resistant delivery systems and the modification of enzyme structures by polymer conjugation or protein engineering. This perspective manuscript reviews and critically discusses recent progress in the oral delivery of therapeutic enzymes, whose substrate is localized in the gastrointestinal tract.

Modular design of redox-responsive stabilizers for nanocrystals

Many potent drugs are difficult to administer intravenously due to poor aqueous solubility. A common approach for addressing this issue is to process them into colloidal dispersions known as "nanocrystals" (NCs). However, NCs possess high-energy surfaces that must be stabilized with surfactants to prevent aggregation. An optimal surfactant should have high affinity for the nanocrystal's surface to stabilize it, but may also include a trigger mechanism that could offer the possibility of altering size distribution and uptake of the NC. This study presents a modular and systematic strategy for optimizing the affinity of polymeric stabilizers for drug nanocrystals both before and after oxidation (i.e., the selected trigger), thus allowing for the optimal responsiveness for a given application to be identified. A library of 10 redox-responsive polymer stabilizers was prepared by postpolymerization modification, using the thiol-yne reaction, of two parent block copolymers. The stabilizing potential of these polymers for paclitaxel NCs is presented as well as the influence of oxidation on size and dissolution following exposure to reactive oxygen species (ROS), which are strongly associated with chronic inflammation and cancer. Owing to the versatility of postpolymerization modification, this contribution provides general tools for preparing triggered-sheddable stabilizing coatings for nanoparticles.

Toxicity of silver nanoparticles in macrophages

Silver nanoparticles (nanosilver) are broadly used today in textiles, food packaging, household devices and bioapplications, prompting a better understanding of their toxicity and biological interactions. In particular, the cytotoxicity of nanosilver with respect to mammalian cells remains unclear, because such investigations can be biased by the nanosilver coatings and the lack of particle size control. Here, nanosilver of well-defined size (5.7 to 20.4 nm) supported on inert nanostructured silica is produced using flame aerosol technology. The cytotoxicity of the prepared nanosilver with respect to murine macrophages is assessed in vitro because these cells are among the first to confront nanosilver upon its intake by mammals. The silica support facilitates the dispersion and stabilization of the prepared nanosilver in biological suspensions, and no other coating or functionalization is applied that could interfere with the biointeractions of nanosilver. Detailed characterization of the particles by X-ray diffraction and electron microscopy reveals that the size of the nanosilver is well controlled. Smaller nanosilver particles release or leach larger fractions of their mass as Ag⁺ ions upon dispersion in water. This strongly influences the cytotoxicity of the nanosilver when incubated with murine macrophages. The size of the nanosilver dictates its mode of cytotoxicity (Ag⁺ ion-specific and/or particle-specific). The toxicity of small nanosilver (<10 nm) is mostly mediated by the released Ag⁺ ions. The influence of such ions on the toxicity of nanosilver decreases with increasing nanosilver size (>10 nm). Direct silver nanoparticle-macrophage interactions dominate the nanosilver toxicity at sizes larger than 10 nm.

Broad control of disulfide stability through microenvironmental effects and analysis in complex redox environments

Disulfide bonds stabilize the tertiary- and quaternary structure of proteins. In addition, they can be used to engineer redox-sensitive (bio)materials and drug-delivery systems. Many of these applications require control of the stability of the disulfide bond. It has recently been shown that the charged microenvironment of the disulfide can be used to alter their stability by ∼3 orders of magnitude in a predictable and finely tunable manner at acidic pH. The aim of this work is to extend these findings to physiological pH and to demonstrate the validity of this approach in complex redox milieu. Disulfide microenvironments were manipulated synergistically with steric hindrance herein to control disulfide bond stability over ∼3 orders of magnitude at neutral pH. Control of disulfide stability through microenvironmental effects could also be observed in complex redox buffers (including serum) and in the presence of cells. Such fine and predictable control of disulfide properties is not achievable using other existing approaches. These findings provide easily implementable and general tools for controlling the responsiveness of biomaterials and drug delivery systems toward various local endogenous redox environments.

Dynamics of lymphatic regeneration and flow patterns after lymph node dissection

Knowledge about the mechanisms of regeneration of the lymphatic vasculature after surgical trauma is essential for the development of strategies for the prevention and therapy of lymphedema. However, little is known about the alterations of lymphatic flow directly after surgical trauma. We investigated lymphatic function in mice using near-infrared imaging for a period of 4 weeks after surgeries that mimic sentinel lymph node biopsy (SLNB) or axillary lymph node dissection (ALND), by removal of the popliteal lymph node (LN) alone or together with the popliteal fat pad, respectively. SLNB-like surgery did not cause changes in lymphatic drainage in the majority of cases. In contrast, lymphatic drainage impairment shown by collecting vessel rupture, dermal backflow and rerouting of lymph flow via collateral vessels were observed after ALND-like surgery. All collateral vessels drained to the inguinal LN. These results indicate that less invasive surgery prevents lymphatic decompensation. They also reveal the development and maturation of collateral lymphatic vessels after extensive surgical trauma, which reroute the flow of lymph towards a different LN. These findings might be helpful for the development of strategies to prevent and/or treat post-surgical lymphedema.

Use of a PEG-conjugated bright near-infrared dye for functional imaging of rerouting of tumor lymphatic drainage after sentinel lymph node metastasis

Tumor lymphangiogenesis promotes metastatic cancer spread to lymph nodes and beyond. However, the potential remodeling and functionality of tumor-draining lymphatic vessels has remained unclear. Thus, we aimed to develop non-invasive imaging methods for repeated quantitative imaging of lymphatic drainage and of contractile collecting lymphatic vessel function in mice, with colloidal near-infrared (NIR) tracers and a custom fluorescence stereomicroscope specially adapted for NIR sensitive imaging. Using these tools, we quantitatively determined pulse rates and valvular function of collecting lymphatic vessels with high resolution. Unexpectedly, we found that tumor-draining lymphatic vessels in a melanoma footpad model initially were dilated but remained functional, despite lower pulse rates. In two independent tumor models, impaired lymphatic function was detected once metastases were present in draining lymph nodes. Importantly, we found that lymphatic dysfunction, induced by metastatic tumor spread to sentinel lymph nodes, can lead to a rerouting of lymphatic flow away from the metastatic lymph node, via collateral lymphatic vessels, to alternate lymph nodes. These findings might have important clinical implications for the procedure of sentinel lymph node mapping that represents the standard of care for determining prognosis and treatment of melanoma and breast cancer patients.

Non-invasive dynamic near-infrared imaging and quantification of vascular leakage in vivo

Preclinical vascular research has been hindered by a lack of methods that can sensitively image and quantify vascular perfusion and leakage in vivo. In this study, we have developed dynamic near-infrared imaging methods to repeatedly visualize and quantify vascular leakage in mouse skin in vivo, and we have applied these methods to transgenic mice with overexpression of vascular endothelial growth factors VEGF-A or -C. Near-infrared dye conjugates were developed to identify a suitable vascular tracer that had a prolonged circulation lifetime and slow leakage into normal tissue after intravenous injection. Dynamic simultaneous imaging of ear skin and a large blood vessel in the leg enabled determination of the intravascular signal (blood volume fraction) from the tissue signal shortly after injection and quantifications of vascular leakage into the extravascular tissue over time. This method allowed for the sensitive detection of increased blood vascularity and leakage rates in K14-VEGF-A transgenic mice and also reliably measured inflammation-induced changes of vascularity and leakage over time in the same mice. Measurements after injection of recombinant VEGF-A surprisingly revealed increased blood vascular leakage and lymphatic clearance in K14-VEGF-C transgenic mice which have an expanded cutaneous lymphatic vessel network, potentially indicating unanticipated effects of lymphatic drainage on vascular leakage. Increased vascular leakage was also detected in subcutaneous tumors, confirming that the method can also be applied to deeper tissues. This new imaging method might facilitate longitudinal investigations of the in vivo effects of drug candidates, including angiogenesis inhibitors, in preclinical disease models.

siRNA transfection with calcium phosphate nanoparticles stabilized with PEGylated chelators

Despite the enormous therapeutic potential of siRNAs, their delivery is still problematic due to unfavorable biodistribution profiles and poor intracellular bioavailability. Calcium phosphate co-precipitate has been used for nearly 40 years for in vitro transfection due to its non-toxic nature and simplicity of preparation. However, rapid particle growth has largely prevented the translation of this method for in vivo purposes. It has recently been shown that bisphosphonate derivatives can physically stabilize calcium phosphate nanoparticles while still allowing for efficient cell transfection with plasmid DNA. Herein, two novel PEGylated chelating agents (PEG-alendronate and PEG-inositolpentakisphosphate) with enhanced stabilizing properties are introduced, and it is demonstrated that the bisphosphonate-stabilized nanoparticles can efficiently deliver siRNA in vitro. The nanoparticles are mainly taken up by clathrin-dependent endocytosis, and acidification of the endosomal compartment is required to release the entrapped siRNA into the cytosol. Furthermore, particle uptake enhances the inhibition of the mevalonate pathway by the bisphosphonate in macrophages.

Celiac disease: a challenging disease for pharmaceutical scientists

Celiac disease (CD) is an immune-mediated enteropathy triggered by the ingestion of gluten-containing grains that affects ~1% of the white ethnic population. In the last decades, a rise in prevalence of CD has been observed that cannot be fully explained by improved diagnostics. Genetic predisposition greatly influences the susceptibility of individuals towards CD, though environmental factors also play a role. With no pharmacological treatments available, the only option to keep CD in remission is a strict and permanent exclusion of dietary gluten. Such a gluten-free diet is difficult to maintain because of gluten's omnipresence in food (e.g., additive in processed food). The development of adjuvant therapies which would permit the intake of small amounts of gluten would be desirable to improve the quality of life of patients on a gluten-free diet. Such therapies include gluten-degrading enzymes, polymeric binders, desensitizing vaccines, anti-inflammatory drugs, transglutaminase 2 inhibitors, and HLA-DQ2 blockers. However, many of these approaches pose pharmaceutical challenges with respect to drug formulation and stability, or application route and dosing interval. This perspective article discusses how pharmaceutical scientists may deal with these challenges and contribute to the implementation of novel therapeutic options for patients with CD.

The interactions of amphiphilic antisense oligonucleotides with serum proteins and their effects on in vitro silencing activity

Antisense oligonucleotides (AONs) are a class of compounds with high therapeutic potential. One of the challenges facing this platform is the development of effective techniques to achieve cellular delivery. AON conjugates, in which traditional AONs are attached to certain biomolecules, can exhibit improved intracellular bioavailability in the absence of delivery systems. In this study, the lipophilic moieties docosahexaenoic acid, cholesterol, and docosanoic acid (DSA) were conjugated to various phosphorothioated DNA and chemically-modified 2'-fluoro-arabinonucleic acid AONs via an amino-hexanol-linker added to the 5'-end of the molecule. The gene silencing potential of these compounds was evaluated in vitro in the absence or presence of a transfecting agent (polyion complex micelle). Incubation with sub-micromolar concentration of DSA-conjugates could, in the absence of serum proteins, downregulate more than 60% of the targeted mRNA under carrier-free and carrier-loaded delivery methods. Gene silencing activity of carrier-free DSA-conjugates was, however, decreased in a dose-dependent fashion by adding albumin in the transfection medium. Supplementing the medium with free fatty acid prevented the interaction of the DSA-conjugate with albumin, and restored its silencing activity. These findings suggest that strategies aiming at preventing the association of hydrophobized AONs to serum proteins at the site of action may improve their activity.

Lipase is essential for the study of in vitro release kinetics from organogels

In vitro drug release studies remain indispensable in the development of drug delivery systems, even if correlations between in vitro and in vivo results are often imperfect. In this work, an improved in vitro analysis method for studying in situ-forming lipid-based implants was developed. More specifically, lipase was found to be an essential additive for evidencing differences in drug release kinetics from organogels of different amino acid-based organogelators, organogelator concentrations, drug loadings, and volumes. Lipases are thought to participate in the degradation of and release from amino acid-based organogel implants in vivo. Our experimental conditions allowed for the rapid and reliable screening of in vitro parameters that may be optimized to slow or accelerate drug release, once preliminary in vivo data are available.