Cytosine-Functionalized Supramolecular Polymer-Mediated Cellular Behavior and Wound Healing.

Physically cross-linked supramolecular polymers composed of a hydrophobic poly(epichlorohydrin) backbone with hydrogen-bonding cytosine pendant groups and hydrophilic poly(ethylene glycol) (PEG) side chains spontaneously self-assemble to form highly controlled, reversible supramolecular polymer networks (SPNs) because of cytosine-induced transient cross-linking. Owing to their simple synthesis procedure and ease of tuning the cytosine and PEG contents to obtain varying degrees of SPNs within the polymer matrix, the resulting polymers exhibit a unique surface morphology, wide-range tunable mechanical/rheological properties, and surface wettability behavior as well as high biocompatibility and structural stability in normal cell- and red blood cell-rich media. Cell culture experiments and fluorescent images clearly demonstrated that the incorporation of cytosine and PEG units into the SPN-based polymer substrates efficiently promoted cellular attachment and accelerated cell growth. Importantly, scratch wound-healing assays revealed that the cytosine-functionalized substrates promoted rapid cell spreading and migration into the damaged cellular surface and accelerated the wound-healing rate. These results indicate that the presence of cytosine units within polymer substrates is crucial for the construction of multifunctional tissue engineering scaffolds with tailorable physical characteristics in order to promote cell adhesion, proliferation, and differentiation.

Hydrogen-bonded cytosine-endowed supramolecular polymeric nanogels: Highly efficient cancer cell targeting and enhanced therapeutic efficacy.

We demonstrate that cytosine moieties within physically cross-linked supramolecular polymers not only manipulate drug delivery and release, but also confer specific targeting of cancer cells to effectively enhance the safety and efficacy of chemotherapy-and thus hold significant potential as a new perspective for development of drug delivery systems. Herein, we successfully developed physically cross-linked supramolecular polymers (PECH-PEG-Cy) comprised of hydrogen-bonding cytosine pendant groups, hydrophilic poly(ethylene glycol) side chains, and a hydrophobic poly(epichlorohydrin) main chain. The polymers spontaneously self-assemble into a reversibly hydrogen-bonded network structure induced by cytosine and directly form spherical nanogels in aqueous solution. Nanogels with a high hydrogen-bond network density (i.e., a higher content of cytosine moieties) exhibit outstanding long-term structural stability in cell culture substrates containing serum, whereas nanogels with a relatively low hydrogen-bond network density cannot preserve their structural integrity. The nanogels also exhibit numerous unique physicochemical characteristics in aqueous solution, such as a desirable spherical size, high biocompatibility with normal and cancer cells, excellent drug encapsulation capacity, and controlled pH-responsive drug release properties. More importantly, in vitro experiments conclusively indicate the drug-loaded PECH-PEG-Cy nanogels can selectively induce cancer cell-specific apoptosis and cell death via cytosine receptor-mediated endocytosis, without significantly harming normal cells. In contrast, control drug-loaded PECH-PEG nanogels, which lack cytosine moieties in their structure, can only induce cell death in cancer cells through non-specific pathways, which significantly inhibits the induction of apoptosis. This work clearly demonstrates that the cytosine moieties in PECH-PEG-Cy nanogels confer selective affinity for the surface of cancer cells, which enhances their targeted cellular uptake, cytotoxicity, and subsequent induction of programmed cell death in cancer cells.