Chemical Reactions in Living Systems

Using Chemistry To Recreate the Complexity of the Extracellular Matrix: Guidelines for Supramolecular Hydrogel-Cell Interactions

Hydrogels have emerged as a promising class of extracellular matrix (ECM)-mimicking materials in regenerative medicine. Here, we briefly describe current state-of-the-art of ECM-mimicking hydrogels, ranging from natural to hybrid to completely synthetic versions, giving the prelude to the importance of supramolecular interactions to make true ECM mimics. The potential of supramolecular interactions to create ECM mimics for cell culture is illustrated through a focus on two different supramolecular hydrogel systems, both developed in our laboratories. We use some recent, significant findings to present important design principles underlying the cell-material interaction. To achieve cell spreading, we propose that slow molecular dynamics (monomer exchange within fibers) is crucial to ensure the robust incorporation of cell adhesion ligands within supramolecular fibers. Slow bulk dynamics (stress-relaxation─fiber rearrangements, τ1/2 ≈ 1000 s) is required to achieve cell spreading in soft gels (<1 kPa), while gel stiffness overrules dynamics in stiffer gels. Importantly, this resonates with the findings of others which specialize in different material types: cell spreading is impaired in case substrate relaxation occurs faster than clutch binding and focal adhesion lifetime. We conclude with discussing considerations and limitations of the supramolecular approach as well as provide a forward thinking perspective to further understand supramolecular hydrogel-cell interactions. Future work may utilize the presented guidelines underlying cell-material interactions to not only arrive at the next generation of ECM-mimicking hydrogels but also advance other fields, such as bioelectronics, opening up new opportunities for innovative applications.

Surface-Bioengineered Extracellular Vesicles Seeking Molecular Biotargets in Lung Cancer Cells

Personalized medicine is a new approach to modern oncology. Here, to facilitate the application of extracellular vesicles (EVs) derived from lung cancer cells as potent advanced therapy medicinal products in lung cancer, the EV membrane was functionalized with a specific ligand for targeting purposes. In this role, the most effective heptapeptide in binding to lung cancer cells (PTHTRWA) was used. The functionalization process of EV surface was performed through the C- or N-terminal end of the heptapeptide. To prove the activity of the EVs functionalized with PTHTRWA, both a model of lipid membrane mimicking normal and cancerous cell membranes as well as human adenocarcinomic alveolar basal epithelial cells (A549) and human normal bronchial epithelial cells (BEAS-2B) have been exposed to these bioconstructs. Magnetic resonance imaging (MRI) showed that the as-bioengineered PTHTRWA-EVs loaded with superparamagnetic iron oxide nanoparticle (SPIO) cargos reach the growing tumor when dosed intravenously in NUDE Balb/c mice bearing A549 cancer. Molecular dynamics (MD) in silico studies elucidated a high affinity of the synthesized peptide to the α5β1 integrin. Preclinical safety assays did not evidence any cytotoxic or genotoxic effects of the PTHTRWA-bioengineered EVs.

Dual-Stimuli Regulation of DNAzyme Cleavage Reaction by Coordination-Driven Nanoprobes for Cancer Cell Imaging

Endowing current artificial chemical reactions (ACRs) with high specificity and intricate activation capabilities is crucial for expanding their applications in accurate bioimaging within living cells. However, most of the reported ACR-based evaluations relied on either single biomarker stimuli or dual activators without obvious biological relevance, still limiting their accuracy and fidelity. Herein, taking the metal-ion-dependent DNAzyme cleavage reaction as a model ACR, two regulators, glutathione (GSH) and telomerase (TE) activated DNAzyme cleavage reactions, were exploited for precise discrimination of cancerous cells from normal cells. DNA probe was self-assembled into the ZIF-90 nanoparticle framework to construct coordination-driven nanoprobes. This approach enhances the stability and specificity of tumor imaging by utilizing biomarkers associated with rapid tumor proliferation and those commonly overexpressed in tumors. In conclusion, the research not only paves the way for new perspectives in cell biology and pathology studies but also lays a solid foundation for the advancement of biomedical imaging and disease diagnostic technologies.

Minimally invasive delivery of human umbilical cord-derived mesenchymal stem cells by an injectable hydrogel via Diels-Alder click reaction for the treatment of intrauterine adhesions

Intrauterine adhesions (IUA) are the most common cause of uterine infertility, and conventional treatments have not consistently achieved satisfactory pregnancy rates. Stem cell therapy shows promising potential for the clinical treatment of IUA. Although various advanced biomaterials have been designed for delivering stem cells to the uterine cavity, there remain significant challenges, particularly in devising therapeutic strategies for clinical application that minimize surgical incisions and conform to the intricate structure of uterine cavity. Herein, an injectable hydrogel loaded with human umbilical cord-derived mesenchymal stem cells (UCMSCs) was synthesized via the Diels-Alder click reaction for endometrial regeneration and fertility restoration, exhibiting suitable mechanical properties, good biocompatibility, and desirable degradation properties. Notably, this hydrogel permitted minimally invasive administration and integrated seamlessly with surrounding tissue. Our study revealed that the UCMSCs-laden injectable hydrogel enhanced cell proliferation, migration, angiogenesis, and exhibited anti-fibrotic effects in vitro. The implantation of this hydrogel significantly facilitated endometrium regeneration and restored fertility in a rat endometrial damage model. Mechanistically, in vivo results indicated that the UCMSCs-laden injectable hydrogel effectively promoted macrophage recruitment and facilitated M2 phenotype polarization. Collectively, this hydrogel demonstrated efficacy in regenerating damaged endometrium, leading to the restoration of fertility. Consequently, it holds promise as a potential therapeutic strategy for endometrial damage and fertility decline arising from intrauterine adhesions. STATEMENT OF SIGNIFICANCE: Severe endometrial traumas frequently lead to intrauterine adhesions and subsequent infertility. Stem cell therapy shows promising potential for the clinical treatment of IUA; however, challenges remain, including low delivery efficiency and compromised stem cell activity during the delivery process. In this study, we fabricated an injectable hydrogel loaded with UCMSCs via the Diels-Alder click reaction, which exhibited unique bioorthogonality. The in situ-gelling hydrogels could be introduced through a minimally invasive procedure and adapt to the intricate anatomy of the uterus. The UCMSCs-laden injectable hydrogel promoted endometrial regeneration and fertility restoration in a rat endometrial damage model, efficaciously augmenting macrophage recruitment and promoting their polarization to the M2 phenotype. The administration of UCMSCs-laden injectable hydrogel presents a promising therapeutic strategy for patients with severe intrauterine adhesion.

Copper-Catalyzed Azide-Alkyne Cycloaddition-Oriented Multifunctional Bio-Orthogonal Linker BPPA: Design, Synthesis and Evaluation

The multifunctional linker molecules are crucial for the bio-orthogonal reaction for proteomic target profiling. Herein, we wish to present a novel type of biotin-based tetra-functional bio-orthogonal linkers 3a-3h named BPPA which, possessing a unique photolabile phenacyl ester motif, were readily prepared in 85-90% yields by a simple and green one-step protocol from commercially available and inexpensive reagents of biotin acids and 4'-ethynyl/azido 2-bromoacetophenones. The typical click reaction of BPPA linkers 3a and 3e via copper-catalyzed azide-alkyne cycloaddition (CuAAC) took place easily, resulting in the corresponding BPPA-triazole adducts 4a and 4b in nearly quantitative yields. A further cleavability evaluation of 4a and 4b demonstrated that the expected C-O bond detachment could be accomplished efficiently and rapidly by UV irradiation or by ammonia hydrolysis, respectively, resulting in the residual (hydroxyl)acetylphenyl triazole fragment supposed to be attached to proteins during biological manipulations. The BPPA linkers, with dual clickable options of either the terminal azide or alkyne clickable group, exhibit high potentials for various CuAAC-oriented bio-orthogonal reactions.