Polypseudorotaxane Constructed from Cationic Polymer with Cucurbit[7]uril for Controlled Antibacterial Activity

This letter is aimed to develop a general strategy to fabricate polypseudorotaxanes with controlled antibacterial activity based on cationic polymers. As a proof of concept, the commercially available antibacterial cationic polymer, ε-poly-l-lysine hydrochloride, was chosen for the demonstration. Using host–guest chemistry, cucurbit[7]­uril (CB[7]), a water-soluble macrocyclic host, was employed to bind with the positive charge and hydrophobic component on ε-poly-l-lysine hydrochlorides for antibacterial regulation. In this way, by tuning the ratio of CB[7] to the cationic polymer, the antibacterial polypseudorotaxane can be obtained, and the antibacterial efficiency can be well tuned from 5% to 100%. This line of research will enrich the field of cationic polymers and polypseudorotaxanes with important functions on precise control over antibacterial activity

Table1_Effects of extreme cyclic loading on the cushioning performance of human heel pads under engineering test condition.xlsx

Human heel pads commonly undergo cyclic loading during daily activities. Low cyclic loadings such as daily human walking tend to have less effect on the mechanical properties of heel pads. However, the impact of cyclic loading on cushion performance, a vital biomechanical property of heel pads, under engineering test condition remains unexplored. Herein, dynamic mechanical measurements and finite element (FE) simulations were employed to explore this phenomenon. It was found that the wavy collagen fibers in the heel pad will be straightened under cycle compression loading, which resulted in increased stiffness of the heel pad. The stiffness of the heel pads demonstrated an inclination to escalate over a span of 50,000 loading cycles, consequently resulting in a corresponding increase in peak impact force over the same loading cycles. Sustained cyclic loading has the potential to result in the fracturing of the straightened collagen fibers, this collagen breakage may diminish the stiffness of the heel pad, leading to a reduction in peak impact force. This work enhances understanding of the biomechanical functions of human heel pad and may provide potential inspirations for the innovative development of healthcare devices for foot complex.</p

Water contact angle measurement for the PLGA、PLGA/HA、PLGA/GO and PLGA/GO/HA nanofibrous matrices.

<p>(n = 5;* p < 0.05).</p

Stress–strain curves of the PLGA, PLGA/HA, PLGA/GO, and PLGA/GO/HA nanofibrous matrices were obtained under a cross-head speed of 5 mm/min.

<p>Prior to testing, 4 types of matrices were cut into a rectangular shape, 30 mm in length and 10 mm in width.</p

Proliferation of MC3T3-E1 cells cultured on the nanofibrous matrices for 1 to 7 days in vitro.

<p>P < 0.05, n = 4.</p

Protein adsorption on different nanofibrous matrices.

<p>(a) Fluorescence images of the Rhodamine B labelled BSA adsorption on PLGA, PLGA/HA PLGA/GO and PLGA/GO/HA; (b) The adsorption of protein onto the PLGA, PLGA/HA, PLGA/GO and PLGA/GO/HA nanofibrous matrices. (n = 5;* p < 0.05).</p

Supramolecular Conjugated Polymer Materials for in Situ Pathogen Detection

Cationic poly­(fluorene-<i>co</i>-phenylene) derivative (PFP-NMe₃⁺) forms a supramolecular complex with cucurbit[7]­uril (CB[7]), which could be reversibly disassembled by amantadine (AD) to release PFP-NMe₃⁺ due to the formation of more stable CB[7]/AD complex. The cationic PFP-NMe₃⁺ is an amphiphilic structure and could bind to negatively charged membrane of pathogen by multivalent interactions. Upon the formation of PFP-NMe₃⁺/CB­[7] complex, the CB[7] could bury the side-chain alkyl groups and decreases the hydrophobic interactions of PFP-NMe₃⁺ on the surface of pathogens; thus, PFP-NMe₃⁺ exhibits different interaction modes with pathogens before and after assembly with CB[7]. The PFP-NMe₃⁺/CB­[7] supramolecular complex could be explored as optical sensor for simple, rapid, and in situ detection and discrimination of multiple pathogens by taking advantage of optical signal changes of PFP-NMe₃⁺/CB­[7] complex before and after disassembly by AD on the pathogen surfaces. The new sensor can realize in situ detection and identification of Gram-negative bacteria (<i>E. coli</i>, <i>P. aeruginosa</i>), Gram-positive bacteria (<i>B. subtilis</i>, <i>S. aureus</i>, <i>E. faecalis</i>), and the fungi (<i>C. albicans</i>, <i>S. cerecisiae</i>) and can also discriminate different strains of the same species. Blend samples of these pathogens could be identified successfully as well. In comparison with conventional blood culture-based pathogen assay methods that require at least for 24 h, the PFP-NMe₃⁺/CB­[7] complex only needs 2 h (including pathogen culture, pathogen harvest by centrifuging, and optical assay procedures) to stratify diverse pathogen types and also does not require specific biomarkers or cell labeling

List of genes and primer nucleotide sequences.

<p>List of genes and primer nucleotide sequences.</p

Alizarin Red staining of MC3T3-E1 cells cultured on PLGA, PLGA/GO, PLGA/HA and PLGA/GO/HA nanofibrous matrices at 14 and 21 days.

<p>Alizarin Red staining of MC3T3-E1 cells cultured on PLGA, PLGA/GO, PLGA/HA and PLGA/GO/HA nanofibrous matrices at 14 and 21 days.</p

Supramolecular Strategy Based on Conjugated Polymers for Discrimination of Virus and Pathogens

A conjugated polymer-based supramolecular system is designed for discrimination of virus and microbes. The supramolecular system is composed of cationic polythiophene derivative (PT) and barrel-shaped macrocyclic molecular cucurbit[7]­uril (CB[7]). Because PT and PT/CB[7] complexes possess different interaction manners toward virus and microbes, the rapid and simple discrimination of virus and microbes was realized through polymer fluorescence intensity change assisting with standard linear discriminant analysis (LDA). The supramolecular strategy would expand the idea of designing biological probes and further promote the extensive application of conjugated polymer materials in biosensor field