Self-Assembled Materials and Applications

Analysis of Homo- and Heterotriple Helix Formation of Collagen Model Peptides and Evaluation of Their Stability in a Biological Environment

Self-assembled materials have attracted attention and have been extensively studied because the reversibility of noncovalent interactions allows them to possess various properties, such as stimulus responsiveness and self-healing. Collagen model peptides have an amino acid sequence characteristic of the triple helix region of collagen and exhibit repeatable triple helix formation. Many studies of their applications have used homotrimers, and although some studies on heterotrimers have been reported, few have clarified the details. If the characteristics of heterotrimers can be revealed, they are expected to be applied as new self-assembled materials. In this study, we analyzed the detailed self-assembling properties of hetero- and homohelices formed by (proline-proline-glycine)10 (PPG)10 and (proline-hydroxyproline-glycine)10 (POG)10 to evaluate the potential of the helices for biomedical application. Fluorescein isothiocyanate-labeled (PPG)10 (F(PPG)10) and (POG)10 (F(POG)10) were synthesized to analyze the heterotriple helix formation using concentration quenching based on triple helix formation. When (PPG)10 was added to F(POG)10, the fluorescence intensity did not reach a plateau, while the fluorescence intensity reached about 100% in the other pairs such as (POG)10-F(POG)10, (PPG)10-F(PPG)10, and (POG)10-F(PPG)10. The critical triple helix formation concentration was 7 μM for the heterotrimer prepared under 1:2 mixing conditions of (PPG)10 and (POG)10, 320 μM for [(PPG)10]3, and 4 μM for [(POG)10]3, indicating that the triple helix formation concentration of the heterotrimer is almost half that of [(POG)10]3 but 45 times higher than [(PPG)10]3. Furthermore, the heterotrimer formed at 37 °C was stable after 5 days, which was the same as [(POG)10]3. These results suggest that heterotrimers have different association properties from homotrimers and are expected to be applied in nanotechnology and biomaterials as new self-assembled materials.

An Overview of Supramolecular Platforms Boosting Drug Delivery

Numerous supramolecular platforms inspired by natural self-assembly are exploited as drug delivery systems. The spontaneous arrangement of single building blocks into inorganic and organic structures is determined and controlled by noncovalent forces such as electrostatic interactions, π-π interactions, hydrogen bonds, and van der Waals interactions. This review describes the main structures and characteristics of several building blocks used to obtain stable, self-assembling nanostructures tailored for numerous biological applications. Owing to their versatility, biocompatibility, and controllability, these nanostructures find application in diverse fields ranging from drug/gene delivery, theranostics, tissue engineering, and nanoelectronics. Herein, we described the different approaches used to design and functionalize these nanomaterials to obtain selective drug delivery in a specific disease. In particular, the review highlights the efficiency of these supramolecular structures in applications related to infectious diseases and cancer.

In vivo self-assembled shape-memory polyurethane for minimally invasive delivery and therapy

Advanced elastomers are highly in demand for the fabrication of medical devices for minimally invasive surgery (MIS). Herein, a shape memory and self-healing polyurethane (PCLUSe) composed of semi-crystalline poly(ε-caprolactone) (PCL) segments and interchangeable and antioxidative diselenide bonds was designed and synthesized. The excellent shape memory of PCLUSe contributed to the smooth MIS operation, leading to less surgical wounds than in the case of sternotomy. The diselenide bonds of PCLUSe contributed to the rapid self-healing under 405 nm irradiation within 60 s, and the alleviation of tissue oxidation post injury. After being delivered through a 10 mm diameter trocar onto a beating canine heart by MIS, two shape-recovered PCLUSe films self-assembled (self-healing) into a larger single patch (20 × 10 × 0.2 mm3) under the trigger of laser irradiation in situ, which could efficiently overcome the limited-size problem within MIS and meet a larger treatment area. The diselenide bonds in the PCLUSe cardiac patches protected the myocardium under oxidative stress post myocardial infarction (MI), and significantly maintained the cardiac functions.