A Bioinspired Skin UV Filter with Broadband UV Protection, Photostability, and Resistance to Oxidative Damage.

In recent years, sunscreens' adverse impacts on the environment and biology have gained wide attention. The improvement of sunscreen safety has become one of the major priorities in skin photoprotection research. It is an effective strategy to develop bionic photoprotective materials by simulating the photoprotective mechanism existing in nature. Inspired by the photoprotective mechanisms of skin and plant leaves, the bionic photoprotective material CS-SA-PDA nanosheet was developed using the free radical grafting method and Michael addition, with natural melanin analogue polydopamine (PDA) nanoparticles and plant sunscreen molecular sinapic acid (SA) as sun protection factors and natural polymer chitosan (CS) as the connecting arm. The results show that CS-SA-PDA can effectively shield UVB and UVA due to the possible synergistic effect between PDA and SA. The introduction of polymer CS significantly improved the photostability of SA and reduced the skin permeability of PDA nanoparticles. The CS-SA-PDA nanosheet can also effectively scavenge photoinduced free radicals. Furthermore, in vivo toxicity and anti-UV evaluations confirm that CS-SA-PDA has no skin irritation and is excellent against skin photodamage, which makes it an ideal skin photoprotective material.

Rational design of dual-functional surfaces on polypropylene with antifouling and antibacterial performances via a micropatterning strategy.

The hydrophobicity and inertness of the polypropylene (PP) material surface usually lead to serious biofouling and bacterial infections, which hamper its potential application as a biomedical polymer. Many strategies have been developed to improve its antifouling or antibacterial properties, yet designing a surface to achieve both antifouling and antibacterial performances simultaneously remains a challenge. Herein, we construct a dual-function micropatterned PP surface with antifouling and antibacterial properties through plasma activation, photomask technology and ultraviolet light-induced graft polymerization. Based on the antifouling agent poly(2-methacryloyloxyethyl phosphate choline) (PMPC) and the antibacterial agent quaternized poly(N,N-dimethylamino)ethyl methacrylate (QPDMAEMA), two different micropatterning structures have been successfully prepared: PP-PMPC-QPDMAEMA in which QPDMAEMA is the micropattern and PMPC is the coating polymer, and PP-QPDMAEMA-PMPC in which PMPC is the micropattern and QPDMAEMA is the coating polymer. The composition, elemental distribution and surface morphology of PP-PMPC-QPDMAEMA and PP-QPDMAEMA-PMPC have been thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. Compared with pristine PP, the two types of micropatterned PP films exhibit good surface hydrophilicity as characterized by water contact angle measurements. The results of anti-protein adsorption, platelet adhesion and antibacterial evaluation showed that PP-PMPC-QPDMAEMA and PP-QPDMAEMA-PMPC had good anti-protein adsorption properties, especially for lysozyme (Lyz). They can effectively prevent platelet adhesion, and the anti-platelet adhesion performance of PP-QPDMAEMA-PMPC is slightly better than that of the PP-PMPC-QPDMAEMA sample. The sterilization rate of S. aureus and E. coli is as high as 95% for the two types of micropatterned PP films. Due to the rational design of micropatterns on the PP surface, the two classes of dual-functional PP materials realize both the resistance of protein and platelet adhesion, and the killing of bacteria at the same time. We anticipate that this work could provide a design strategy for the construction of multifunctional biomedical polymer materials.

Construction of multifunctional micro-patterned PALNMA/PDADMAC/PEGDA hydrogel and intelligently responsive antibacterial coating HA/BBR on Mg alloy surface for orthopedic application.

In recent years, magnesium alloys (MgA) have been reckoned as the most promising material of biomedical importance on account of its excellent degradable properties and mechanical properties mimicking natural bone tissues. However, MgA are prone to rapid corrosion under physiological conditions, causing toxicity around the neighboring tissues. In addition, they are susceptible to bacterial colonization, a detrimental factor for medical causes. In this study, antibacterial material coated hydrogel-based micro-patterns were developed on MgA to achieve long-term antibacterial, antifouling, osteogenic, and cell-compatible properties. First, the Mg(OH)2 nanosheet coating was prepared on the surface of MgA as a physical barrier to prevent the corrosion of MgA. Then the hydrogel micropatterns of poly(alendronate sodium methacrylate)/poly(dimethyldiallylammonium chloride)/poly(ethylene glycol) diacrylate (PALNMA/PDADMAC/PEGDA) of different sizes were constructed on the surface of the Mg(OH)2 coating using the photomask method. Finally, an intelligently responsive antibacterial material hyaluronic acid/berberine (HA/BBR) was coated on MgA-Mg(OH)2-PALNMA/PDADMAC/PEGDA patterns via layer-by-layer self-assembly. The excellent antifouling performance of the samples is attributed to the topological structure of the pattern. Interestingly, as the pattern size of PALNMA/PDADMAC/PEGDA decreases, the antibacterial, antifouling, and cell compatibility properties of the samples gradually improve. UV-Vis spectra and bacterial plate count indicate that HA/BBR coating provide a pH and hyaluronidase (HAase) dual-responsive surface to kill the attached bacteria quickly. Finally, the in vitro experiments demonstrate excellent blood compatibility, cell compatibility and osteogenic properties of the modified MgA samples. Therefore, the intelligent multifunctional assembly of MgA presented here has a promising future in the field of metal implant materials.

Functional composite hydrogels entrapping polydopamine hollow nanoparticles for highly efficient resistance of skin penetration and photoprotection.

Living organisms tend to evolve various naturally photoprotective mechanisms to avoid photodamage. Among them, polydopamine (PDA) is an effective sunscreen, a mimic of melanin, which is the main functional component of the photoprotective system of human skin. However, the concerns of its dark color, skin penetration and photoprotective efficiency remain yet to be solved. Herein, we have constructed melanin-inspired nanocomposite hydrogels (CS-PDAh-GP-HA) for photoprotection, in which PDA was prepared as hollow nanoparticles (PDAh NPs) and entrapped in a physically cross-linked hydrogel (CS-GP-HA) formed by chitosan (CS) and hyaluronic acid (HA) using ß-glycerophosphate (ß-GP) as a modulator. The CS-PDAh-GP-HA hydrogels exhibit a shear-thinning flow behavior with an elastic modulus of 300 Pa with the gel-sol transition temperature maintained at about 37 °C simply by adjusting the ß-GP content in the hydrogels. The CS-PDAh-GP-HA hydrogels also possess excellent resistance toward skin penetration. The photoprotective performances of CS-PDAh-GP-HA hydrogels were evaluated by the determination of sun protection factor (SPF) and in vitro UVA protection efficacy (UVAPE) along with UV-Vis spectroscopy. Compared with the TiO2 nanoparticles in CS-GP-HA hydrogel, the CS-PDAh-GP-HA hydrogels show stronger shielding ability in both UVA and UVB regions. When protected by the CS-PDAh-GP-HA hydrogels, the cell viability of NIH-3T3 fibroblasts increases to 96% while it was only 14% in the case of non-protecting group. These results suggest that the CS-PDAh-GP-HA hydrogels could efficiently shield the UV irradiation and protect the skin from photodamage. This work introduces PDA-based nanocomposite hydrogels with safe, biocompatible and photoprotective properties, and provides a melanin-mimicking photoprotection system for the application in sunscreens.

Rational Design of PMPC/PDMC/PEGDA Hydrogel Micropatterns onto Polylactic Acid with Enhanced Biological Activity.

Polylactic acid (PLA) is one of the biodegradable materials that has been used in the areas of surgical healing lines, cancer treatment, and wound healing. However, the application of PLA is still rather limited due to its high hydrophobicity and poor antibacterial activity. In order to enhance the antifouling and antibacterial performances of PLA, here we modified the surface of PLA with various sizes of hydrogel micropatterns in negative or positive mode using plasma treatment, the photomask technique, and UV-graft polymerization. The hydrogel micropatterns consist of poly(ethylene glycol) diacrylate (PEGDA), poly(2-methacryloyloxyethylphosphorylcholine) (PMPC), and poly(methacryloyloxyethyltrimethylammonium chloride) (PDMC). Compared to PLA, the patterned PLA (PLA-PMPC/PDMC/PEGDA) shows obviously enhanced antifouling and antibacterial activities. For PLA-PMPC/PDMC/PEGDA with either positive or negative micropatterns, the antifouling and antibacterial properties are gradually increasing with decreasing the size of micropatterns. Compared with PLA-PMPC/PDMC/PEGDA bearing positive and negative micropatterns in the same size, the PLA-PMPC/PDMC/PEGDA with negative micropatterns exhibits slightly better biological activity and the PLA-PMPC/PDMC/PEGDA with 3 µm negative hydrogel micropatterns shows the best hydrophilicity, antifouling, and antibacterial properties. Combining the in vitro hemolysis assay, cytotoxicity, water absorption test, and degradation test results, it is suggested that the fabrication of hydrogel micropatterns onto the PLA surface could significantly improve biological activities of PLA. We expect that this work would provide a new strategy to potentially develop PLA as a promising wound dressing.

Fabrication of PMPC/PTM/PEGDA micropatterns onto polypropylene films behaving with dual functions of antifouling and antimicrobial activities.

Polymer materials with high biocompatibility and versatile functions are urgently required in the biomedical field. The hydrophobic surface and inert traits of polymer materials usually encounter severe biofouling and bacterial infection which hinder the potential application of polymers as biomedical materials. Although many antifouling or antimicrobial coatings have been developed for modification of biomedical devices/implants, few can simultaneously fulfill the requirements for antimicrobial and antifouling activities. Herein, we constructed bifunctional micropatterns with antifouling and antimicrobial properties onto polypropylene (PP) films using argon plasma activation treatment, photomask technique and UV-initiated graft polymerization method. Different sizes of PMPC/PTM/PEGDA micropatterns were fabricated on PP films to yield patterned PP-PMPC/PTM/PEGDA as evidenced by infrared (IR) spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), where PMPC is poly(2-methacryloyloxyethyl phosphorylcholine) for enhancement of hydrophilicity and biocompatibility, PTM is poly(methacryloyloxyethyltrimethylammonium chloride) for contribution to antimicrobial activity and PEGDA is poly(ethylene glycol diacrylate) as the crosslinker. The surface hydrophilicity of patterned PP-PMPC/PTM/PEGDA was characterized by the static water contact angle test. The results showed that the PP sample with a micropattern with the size of 5 µm exhibited the best hydrophilicity. For biological assays of patterned PP-PMPC/PTM/PEGDA, the micropattern size at 5 µm performed the best for both antiplatelet adhesion and antimicrobial activities. We anticipate that this work could provide a new method for building bifunctional biomedical materials to promote the application of PP in biomedical fields.