To improve water solubility and bioavailability, curcumin (Cur)
was encapsulated by liposomes (Cur-Lip), which was further coated
with thiolated chitosan (CSSH) to form liposomal hydrogels (CSSH/Cur-Lip
gel). The hydrogels were thermosensitive with in situ injectable performance, which were fluidic at room temperature and
gelled quickly at 37 °C. The cumulative release ratio of the
200 μM CSSH/Cur-Lip gel was 31.57 ± 1.34% at 12 h, which
could effectively delay the release of curcumin. Worthily, the resilient
hydrogels were compressive even after five cycles of compression.
The cytotoxicity test indicated that the liposomal hydrogels had good
cytocompatibility, but after encapsulation of curcumin, MCF-7 cells
were suppressed and killed dramatically after 72 h. The in
vivo breast cancer recurrence experiment showed that the
CSSH/Cur-Lip gel inhibited breast cancer recurrence after tumors were
resected, and the tissue of defect in the CSSH/Cur-Lip gel group was
repaired. The results showed that the drug-loaded liposomal hydrogels
can deliver curcumin continuously and exerted an excellent tumoricidal
effect in vitro and in vivo. The
injectable, in situ-formable, and thermosensitive
CSSH/Cur-Lip gel can be designed as a promising novel drug delivery
vehicle to be used as carriers for local accurate and sustained drug
delivery to minimize burst release and as tissue engineering scaffolds
for tissue regeneration after tumor resection.
Selective charge separation among different crystal facets of a semiconductor is an intriguing phenomenon for which there is no firm and full theoretical foundation currently. In this work, we report on a density functional theory + U characterization of band alignment and electron and hole polaron stabilities among the (010), (110), and (011) facets of bismuth vanadate BiVO 4 (BVO). Computation-derived band alignment indicates that the conduction band minima are at nearly the same level among the three facets but that the valence band maxima exhibit a shift. We also modeled electron and hole polarons as localized electrons and holes on vanadium and oxygen, respectively, and determined their relative stabilities from a "bulk" region to a surface region. Calculated stabilities reveal similar stability profiles across the various facets, with electron polarons most stable when localized on subsurface V atoms and hole polarons most stable on surface O atoms. Calculations indicate a small stability preference for electron polarons toward the (011) facet and for hole polarons toward the (110) facet, whereas, experimentally, interfacial reduction is observed to take place selectively on the (010) facet and oxidation on the (110) and (011) facets. Facet selectivity could be occurring on the basis of thermodynamics (electron or holes showing a stronger affinity for some facets over others) or kinetics (electron or hole transport and/or redox processes being more efficient toward/on some facets over others) or a combination of both. This work establishes that thermodynamic stability alone is not responsible for the observed facet selectivity in BVO. Therefore, we surmise that polaron transport kinetics and interfacial redox kinetics are likely to have a role in facet selectivity in BVO. These issues will be the subject of future publications.
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