Abstract
Polystyrene nanospheres (PNs) were embedded in bovine skin gelatin gels with a poly(N-isopropylacrylamide) (PNIPAAm) network, which were denoted as NGHHs, to generate thermoresponsive behavior. When 265 nm PNs were exploited to generate the pores, bovine skin gelatin extended to completely occupy the pores left by PNs below the lower critical solution temperature (LCST), forming a pore-less structure. Contrarily, above the LCST, the collapse of hydrogen bonding between bovine skin gelatin and PNIPAAm occurred, resulting in pores in the NGHH. The behavior of pore closing and opening below and above the LCST, respectively, indicates the excellent drug gating efficiency. Amoxicillin (AMX) was loaded into the NGHHs as smart antibiotic gating due to the pore closing and opening behavior. Accordingly, E. coli. and S. aureus were exploited to test the bacteria inhibition ratio (BIR) of the AMX-loaded NGHHs. BIRs of NGHH without pores were 48% to 46.7% at 25 and 37 °C, respectively, for E. coli during 12 h of incubation time. The BIRs of nanoporous NGHH could be enhanced from 61.5% to 90.4% providing a smart antibiotic gate of bovine skin gelatin gels against inflammation from infection or injury inflammation.
Highlights
Skin burns mostly generate the disruption of the epidermal barrier, combined with the denaturation of proteins and lipids, which is significantly prone to infection due to a fertile environment that is rich in bacterial nutrients for microbial growth [1]
During removal of the Polystyrene nanospheres (PNs), the gelated gelatin networks with stretched PNIPAAm chains in the NGHH membranes shrunk the pore sizes below both upper critical solution temperature (UCST) of gelatin and lower critical solution temperature (LCST) of PNIPAAm; the pore sizes were enlarged by solating gelatin networks with coiled PNIPAAm chains above both the UCST of gelatin and LCST of PNIPAAm
The results suggest that the ca. 265 nm diameter pore left by PNs in the NGHH could be filled completely by bovine skin gelatin in the cross-lined PNIPAAm network below the LCST resulting in pore closing
Summary
Skin burns mostly generate the disruption of the epidermal barrier, combined with the denaturation of proteins and lipids, which is significantly prone to infection due to a fertile environment that is rich in bacterial nutrients for microbial growth [1]. The bovine skin gelatin was retained in the 3D network of cross-linked PNIPAAm to improve the mechanical properties of NGHHs. A series of NGHH scaffolds with thermo-tunable pores was obtained after the removal of PNs. During removal of the PNs, the gelated gelatin networks with stretched PNIPAAm chains in the NGHH membranes shrunk the pore sizes below both UCST of gelatin and LCST of PNIPAAm; the pore sizes were enlarged by solating gelatin networks with coiled PNIPAAm chains above both the UCST of gelatin and LCST of PNIPAAm. A series of porous NGHH membranes exhibited pore closing and opening behavior between 25 and 45 ◦ C by combining the UCST behavior of gelatin and LCST behavior of PNIPAAm, which could be applied for biocompatible smart drug gating. Our thermoresponsive NGHHs are able to release antibiotics against bacteria in the local inflammation or fever environment under infection
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