Oxidation-Sensitive Core-Multishell Nanocarriers for the Controlled Delivery of Hydrophobic Drugs

Stimuli-responsive drug delivery systems for inflammatory skin conditions

Inflammatory skin conditions highly influence the quality of life of the patients suffering from these disorders. Symptoms include red, itchy and painful skin lesions, which are visible to the rest of the world, causing stigmatization and a significantly lower mental health of the patients. Treatment options are often unsatisfactory, as they suffer from either low patient adherence or the risk of severe side effects. Considering this, there is a need for new treatments, and notably of new ways of delivering the drugs. Stimuli-responsive drug delivery systems are able to deliver their drug cargo in response to a given stimulus and are, thus, promising for the treatment of inflammatory skin conditions. For example, the use of external stimuli such as ultraviolet light, near infrared radiation, or alteration of magnetic field enables drug release to be precisely controlled in space and time. On the other hand, internal stimuli induced by the pathological condition, including pH alteration in the skin or upregulation of reactive oxygen species or enzymes, can be utilized to create drug delivery systems that specifically target the diseased skin to achieve a better efficacy and safety. In the latter context, however, it is of key importance to match the trigger mechanism of the drug delivery system to the actual pathological features of the specific skin condition. Hence, the focus of this article is placed not only on reviewing stimuli-responsive drug delivery systems developed to treat specific inflammatory skin conditions, but also on critically evaluating their efficacy in the context of specific skin diseases. STATEMENT OF SIGNIFICANCE: Skin diseases affect one-third of the world's population, significantly lowering the quality of life of the patients, who deal with symptoms such as painful and itchy skin lesions, as well as stigmatization due to the visibility of their symptoms. Current treatments for inflammatory skin conditions are often hampered by low patient adherence or serious drug side effects. Therefore, more emphasis should be placed on developing innovative formulations that provide better efficacy and safety for patients. Stimuli-responsive drug delivery systems hold considerable promise in this regard, as they can deliver their cargo precisely where and when it is needed, reducing adverse effects and potentially offering better treatment outcomes.

Enhanced Stable and Efficient of Dual-Ligand Zirconium-Based Metal-Organic Frameworks for Synergistic Photodynamic Inactivation

Porphyrins, known for generating toxic singlet oxygen (1O2) to combat bacteria, face challenges such as hydrophilicity and limited lifespan and 1O2 yield. Conversely, triterpenoid compounds like ammonium glycyrrhizinate (AG) offer antioxidative and antibacterial properties but lack efficacy and stability. Combining them in Metal-Organic Frameworks (MOFs) yields dual-ligand zirconium (Zr)-basedMOFs (M-TG), capitalizing on porphyrins' membrane-disrupting ability and AG's inhibition of bacterial membrane synthesis for a synergistic antibacterial effect. M-TG resolves activity loss, enhances reactive oxygen species (ROS) yield, and extends stability, achieving a remarkable 99.999% sterilization rate. This innovative approach maximizes ligand properties through synergistic effects, promising significant advancements in antibacterial material design.

Label-free mapping of cetuximab in multi-layered tumor oral mucosa models by atomic force-microscopy-based infrared spectroscopy

Sensitive mapping of drugs and drug delivery systems is pivotal for the understanding and improvement of treatment options. Since labeling alters the physicochemical and potentially the pharmacological properties of the molecule of interest, its label-free detection by photothermal expansion is investigated. We report on a proof-of-concept study to map the cetuximab distribution by atomic-force microscopy-based infrared spectroscopy (AFM-IR). The monoclonal antibody cetuximab was applied to a human tumor oral mucosa model, consisting of a tumor epithelium on a lamina propria equivalent. Hyperspectral imaging in the wavenumber regime between 903 cm-1 and 1312 cm-1 and a probing distance between the data points down to 10 × 10 nm are used for determining the local drug distribution. The local distinction of cetuximab from the tissue background is gained by linear combination modeling making use of reference spectra of the drug and untreated models. The results from this approach are compared to principal component analyses, yielding comparable results. Even single molecule detection appears feasible. The results indicate that cetuximab penetrates the cytosol of tumor cells but does not bind to structures in the cell membrane. In conclusion, AFM-IR mapping of cetuximab proved to sensitively determine drug concentrations at an unprecedented spatial resolution without the need for drug labeling.

Parasitism in Metal Nanoclusters: A Case Study of (AuAg)25·(AuAg)27

Studying the interactions of atomically precise metal nanoclusters in their assembly systems is of great significance in the nanomaterial research field, which has attracted increasing interest in the last few decades. Herein, we report the cocrystallization of two oppositely charged atomically precise metal nanoclusters in one unit cell: [Au1Ag24(SR)18]- ((AuAg)25 for short) and [AuxAg27-x(Dppf)4(SR)9]2+ (x = 10-12; (AuAg)27 for short) with a 1:1 ratio. (AuAg)27 could maintain its structure in the presence of (AuAg)25, whether in the crystalline and the solution state, while the metastable (AuAg)27 component underwent a spontaneous transformation to (AuAg)16(Dppf)2(SR)8 after dissociating the (AuAg)25 component from this cocrystal, demonstrating the "parasitism" relationship of the (AuAg)27 component over (AuAg)25 in this dual-cluster system. This work enriches the family of cluster-based assemblies and elucidates the delicate relationship between nanoparticles of cocrystals.

Visualization of Nanocarriers and Drugs in Cells and Tissue

In this chapter, the visualization of nanocarriers and drugs in cells and tissue is reviewed. This topic is tightly connected to modern drug delivery, which relies on nanoscopic drug formulation approaches and the ability to probe nanoparticulate systems selectively in cells and tissue using advanced spectroscopic and microscopic techniques. We first give an overview of the breadth of this research field. Then, we mainly focus on topical drug delivery to the skin and discuss selected visualization techniques from spectromicroscopy, such as scanning transmission X-ray microscopy and fluorescence lifetime imaging. These techniques rely on the sensitive and quantitative detection of the topically applied drug delivery systems and active substances, either by exploiting their molecular properties or by introducing environmentally sensitive probes that facilitate their detection.

Fluorescent nano- and microparticles for sensing cellular microenvironment: past, present and future applications

The tumor microenvironment (TME) demonstrates distinct hallmarks, including acidosis, hypoxia, reactive oxygen species (ROS) generation, and altered ion fluxes, which are crucial targets for early cancer biomarker detection, tumor diagnosis, and therapeutic strategies. Various imaging and sensing techniques have been developed and employed in both research and clinical settings to visualize and monitor cellular and TME dynamics. Among these, ratiometric fluorescence-based sensors have emerged as powerful analytical tools, providing precise and sensitive insights into TME and enabling real-time detection and tracking of dynamic changes. In this comprehensive review, we discuss the latest advancements in ratiometric fluorescent probes designed for the optical mapping of pH, oxygen, ROS, ions, and biomarkers within the TME. We elucidate their structural designs and sensing mechanisms as well as their applications in in vitro and in vivo detection. Furthermore, we explore integrated sensing platforms that reveal the spatiotemporal behavior of complex tumor cultures, highlighting the potential of high-resolution imaging techniques combined with computational methods. This review aims to provide a solid foundation for understanding the current state of the art and the future potential of fluorescent nano- and microparticles in the field of cellular microenvironment sensing.

Efficacy of topically applied rapamycin-loaded redox-sensitive nanocarriers in a human skin/T cell co-culture model

Rapamycin, also known as Sirolimus, is a promising anti-proliferative drug, but its therapeutic use for the topical treatment of inflammatory, hyperproliferative skin disorders is limited by insufficient penetration rates due to its high molecular weight (MW of 914.172 g/mol) and high lipophilicity. We have shown that core multi-shell (CMS) nanocarriers sensitive to oxidative environment can improve drug delivery to the skin. In this study, we investigated the mTOR inhibitory activity of these oxidation-sensitive CMS (osCMS) nanocarrier formulations in an inflammatory ex vivo human skin model. In this model, features of inflamed skin were introduced by treating the ex vivo tissue with low-dose serine protease (SP) and lipopolysaccharide (LPS), while phorbol 12-myristate 13-acetate and ionomycin were used to stimulate IL-17A production in the co-cultured SeAx cells. Furthermore, we tried to elucidate the effects of rapamycin on single cell populations isolated from skin (keratinocytes, fibroblast) as well as on SeAx cells. Further, we measured possible effects of the rapamycin formulations on dendritic cell (DC) migration and activation. The inflammatory skin model enabled the assessment of biological readouts at both the tissue and T cell level. All investigated formulations successfully delivered rapamycin across the skin as revealed by reduced IL-17A levels. Nevertheless, only the osCMS formulations reached higher anti-inflammatory effects in the skin compared to the control formulations with a significant downregulation of mTOR activity. These results indicate that osCMS formulations could help to establish rapamycin, or even other drugs with similar physico-chemical properties, in topical anti-inflammatory therapy.

Random versus Block Glycopolymers Bearing Betulin and Porphyrin for Enhanced Photodynamic Therapy

Porphyrins and their derivatives, representing the second-generation photosensitizers, can generate reactive oxygen species (ROS) and kill tumors upon light irradiation. To compensate for the fluorescence quenching and reduced ROS production caused by aggregation and rigid inherent hydrophobicity of porphyrins, a series of comparable random and block glycopolymers bearing betulin and porphyrin were prepared via RAFT polymerization. Betulin was introduced into the copolymers to decrease aggregation-induced quenching of porphyrins and to improve the photodynamic therapy (PDT) efficiency of copolymers. The characteristics, self-assembly, and photophysical chemistry properties of these copolymers were systemically studied. The effect of polymer structure on photophysical chemistry properties and cellular interaction was investigated as well to demonstrate their potential targeting for PDT applications.

Biodegradable core-multishell nanocarrier: Topical tacrolimus delivery for treatment of dermatitis

Two challenges in topical drug delivery to the skin include solubilizing hydrophobic drugs in water-based formulations and increasing drug penetration into the skin. Polymeric core-multishell nanocarrier (CMS), particularly the novel biodegradable CMS (bCMS = hPG-PCL_1.1K-mPEG_2k-CMS) have shown both advantages on excised skin ex vivo. Here, we investigated topical delivery of tacrolimus (TAC; > 500 g/mol) by bCMS in a hydrogel on an oxazolone-induced model of dermatitis in vivo. As expected, bCMS successfully delivered TAC into the skin. However, in vivo they did not increase, but decrease TAC penetration through the stratum corneum compared to ointment. Differences in the resulting mean concentrations were mostly non-significant in the skin (epidermis: 35.7 ± 20.9 ng/cm² for bCMS vs. 92.6 ± 62.7 ng/cm² for ointment; dermis: 76.8 ± 26.8 ng/cm²vs 118.2 ± 50.4 ng/cm²), but highly significant in blood (plasma: 1.1 ± 0.4 ng/ml vs 11.3 ± 9.3 ng/ml; erythrocytes: 0.5 ± 0.2 ng/ml vs 3.4 ± 2.4 ng/ml) and liver (0.01 ± 0.01 ng/mg vs 0.03 ± 0.01 ng/mg). bCMS were detected in the stratum corneum but not in viable skin or beyond. The therapeutic efficacy of TAC delivered by bCMS was equivalent to that of standard TAC ointment. Our results suggest that bCMS may be a promising carrier for the topical delivery of TAC. The quantitative difference to previous results should be interpreted in light of structural differences between murine and human skin, but highlights the need as well as potential methods to develop more a complex ex vivo analysis on human skin to ensure quantitative predictive value.

Novel Adhesive Nanocarriers Based on Mussel-Inspired Polyglycerols for the Application onto Mucosal Tissues

A synthetic route for adhesive core-multishell (CMS) nanocarriers for application to the oral mucosa was established using mussel-inspired catechol moieties. The three CMS nanocarriers with 8%, 13%, and 20% catechol functionalization were evaluated for loading capacity using Nile red, showing an overall loading of 1 wt%. The ability of Nile red loaded and functionalized nanocarriers to bind to a moist mucosal surface was tested in two complementary adhesion assays under static and dynamic conditions using monolayers of differentiated gingival keratinocytes. Adhesion properties of functionalized nanocarriers were compared to the adhesion of the non-functionalized nanocarrier. In both assays, the CMS nanocarrier functionalized with 8% catechol exhibited the strongest adhesion compared to its catechol-free counterpart and the CMS nanocarriers functionalized with 13% and 20% catechol.

Enhanced Anticancer Efficacy of Chemotherapy by Amphiphilic Y-Shaped Polypeptide Micelles

Although the treatment modalities of cancers are developing rapidly, chemotherapy is still the primary treatment strategy for most solid cancers. The progress in nanotechnology provides an opportunity to upregulate the tumor suppression efficacy and decreases the systemic toxicities. As a promising nanoplatform, the polymer micelles are fascinating nanocarriers for the encapsulation and delivery of chemotherapeutic agents. The chemical and physical properties of amphiphilic co-polymers could significantly regulate the performances of the micellar self-assembly and affect the behaviors of controlled release of drugs. Herein, two amphiphilic Y-shaped polypeptides are prepared by the ring-opening polymerization of cyclic monomer l-leucine N-carboxyanhydride (l-Leu NCA) initiated by a dual-amino-ended macroinitiator poly(ethylene glycol) [mPEG-(NH2)2]. The block co-polypeptides with PLeu8 and PLeu16 segments could form spontaneously into micelles in an aqueous solution with hydrodynamic radii of 80.0 ± 6.0 and 69.1 ± 4.8 nm, respectively. The developed doxorubicin (DOX)-loaded micelles could release the payload in a sustained pattern and inhibit the growth of xenografted human HepG2 hepatocellular carcinoma with decreased systemic toxicity. The results demonstrated the great potential of polypeptide micellar formulations in cancer therapy clinically.

Influence of Nanogel Amphiphilicity on Dermal Delivery: Balancing Surface Hydrophobicity and Network Rigidity

Polymeric nanogels are promising nonirritating nanocarriers for topical delivery applications. However, conventional hydrophilic networks limit encapsulation of hydrophobic therapeutics and hinder tailored interactions with the amphiphilic skin barrier. To address these limitations, we present amphiphilic nanogels containing hydrophilic networks with hydrophobic domains. Two competing factors determine favorable nanogel-skin interactions and need to be balanced through network composition: suitable surface hydrophobicity and low network rigidity (through physical hydrophobic cross-links). To ensure comparability in such investigations, we prepared a library of nanogels with increasing hydrophobic cholesteryl amounts but similar colloidal features. By combining mechanical and surface hydrophobicity tests (atomic force microscopy (AFM)) with dermal delivery experiments on excised human skin, we can correlate an increased delivery efficacy of Nile red to the viable epidermis with a specific network composition, i.e., 20-30 mol % cholesterol. Thus, our nanogel library identifies a specific balance between surface amphiphilicity and network rigidity to guide developments of advanced dermal delivery vehicles.

Topical Delivery of Rapamycin by Means of Microenvironment-Sensitive Core-Multi-Shell Nanocarriers: Assessment of Anti-Inflammatory Activity in an ex vivo Skin/T Cell Co-Culture Model

Introduction

Rapamycin (Rapa) is an immunosuppressive macrolide that inhibits the mechanistic target of rapamycin (mTOR) activity. Thanks to its anti-proliferative effects towards different cell types, including keratinocytes and T cells, Rapa shows promise in the treatment of skin diseases characterized by cell hyperproliferation. However, Rapa skin penetration is limited due to its lipophilic nature (log P = 4.3) and high molecular weight (MW = 914 g/mol). In previous studies, new microenvironment-sensitive core multishell (CMS) nanocarriers capable of sensing the redox state of inflamed skin were developed as more efficient and selective vehicles for macrolide delivery to inflamed skin.

Methods

In this study, we tested such redox-sensitive CMS nanocarriers using an inflammatory skin model based on human skin explants co-cultured with Jurkat T cells. Serine protease (SP) was applied on skin surface to induce skin barrier impairment and oxidative stress, whereas phytohaemagglutinin (PHA), IL-17A, and IL-22 were used to activate Jurkat cells. Activation markers, such as CD45 and CD69, phosphorylated ribosomal protein S6 (pRP-S6), and IL-2 release were monitored in activated T cells, whereas pro-inflammatory cytokines were measured in skin extracts and culture medium.

Results

We found that alteration of skin barrier proteins corneodesmosin (CDSN), occludin (Occl), and zonula occludens-1 (ZO-1) as well as oxidation-induced decrease of free thiol groups occurred upon SP-treatment. All Rapa formulations exerted inhibitory effects on T cells after penetration across ex vivo skin. No effects on skin inflammatory markers were detected. The superiority of the oxidative-sensitive CMS nanocarriers over the other formulations was observed with regard to drug delivery as well as downregulation of IL-2 release.

Conclusion

Overall, our results demonstrate that nanocarriers addressing features of diseased skin are promising approaches to improve the topical delivery of macrolide drugs.