Risk factors of musculoskeletal disorders in loading and unloading tasks of couriers.

BACKGROUND: The use of home delivery services has expanded due to coronavirus disease - 2019, and couriers' high level of work intensity has become a severe social issue in various nations. OBJECTIVE: This study investigates the risk factors of musculoskeletal disorders (MSDs) caused by frequent loading and unloading actions, known to be the most demanding tasks for couriers. METHODS: A self-report survey and post-hoc interview were employed to collect personal information, task frequency, and the incidence of MSDs. Frequent actions during loading and unloading packages were identified, and the Rapid Entry Body Assessment (REBA) and National Institute for Occupational Safety and Health (NIOSH) lifting equations were assessed. RESULTS: Approximately 29.5% of the 44 subjects suffered from MSDs, and identify the types of actions that frequently occur during loading and unloading packages. According to the REBA survey, 60% of the responses for both loading and unloading are distributed within the risk range of 8-13 points, suggesting a high risk (mean REBA score: 8.8 (loading), 8.5 (unloading)). In every case, NIOSH determined that the lifting index (LI) was harmful (mean LI: 1.62). Thereby, the bending or twisting posture of the hands and neck, long horizontal distance between the packages and the body, and high lifting frequency were identified as major problems. CONCLUSION: The study identified a very high level of musculoskeletal risk for couriers, and the detailed working methods and body parts vulnerable to MSDs.

Fabrication of a Tailored, Hybrid Extracellular Matrix Composite.

The extracellular matrix (ECM) is a network of connective fibers that supports cells living in their surroundings. Native ECM, generated by the secretory products of each tissue's resident cells, has a unique architecture with different protein composition depending on the tissue. Therefore, it is very difficult to artificially design in vivo architecture in tissue engineering. In this study, a hybrid ECM scaffold from the basic structure of fibroblast-derived cellular ECMs is fabricated by adding major ECM components of fibronectin (FN) and collagen (COL I) externally. It is confirmed that while maintaining the basic structure of the native ECM, major protein components can be regulated. Then, decellularization is performed to prepare hybrid ECM scaffolds with various protein compositions and it is demonstrated that a liver-mimicking fibronectin (FN)-rich hybrid ECM promoted successful settling of H4IIE rat hepatoma cells. The authors believe that their method holds promise for the fabrication of scaffolds that provide a tailored cellular microenvironment for specific organs and serve as novel pathways for the replacement or regeneration of specific organ tissues.

Cross-Linked Polymersomes with Reversible Deformability and Oxygen Transportability.

Polymersomes are of interest as nanocarriers due to their physical and chemical robustness, which arises from the macromolecular nature of their block copolymer components. However, the physical robustness of polymersomes impairs transmembrane diffusion and responsiveness to mechanical forces. Polymer nanocarriers that can reversibly deform under stress while maintaining structural integrity and transmembrane diffusivity are desired for development of gas transport vehicles. Here, we report polymersomes composed of amphiphilic block copolymers containing polydimethylsiloxane with side-chain pendant vinyl groups. A reversibly deformable polymersome compartmentalizing membrane was obtained by cross-linkage of PEG- b-poly(dimethyl- r-methylvinyl)silane in a self-assembled bilayer via photoradical generation in aqueous media. The covalently cross-linked polymersomes exhibited superior physical robustness compared to unlinked polymersomes while maintaining deformability under stress. Transmembrane oxygen diffusion was confirmed when lumen-encapsulated Zn-porphyrin generated singlet O2 under irradiation, and the anthracene-9,10-dipropionic acid O2 quencher was consumed. Polymersome-encapsulated hemoglobin bound oxygen reversibly, indicating the polymersomes could be used as O2 carriers that reversibly deform without sacrificing structural integrity or oxygen transportability.