Multifunctional
hydrogel-based wound dressings have been explored
for decades due to their huge potential in multifaceted medical intervention
to wound healing. However, it is usually not easy to fabricate a single
hydrogel with all of the desirable functions at one time. Herein,
a bilayer model with an outer layer for hydrogel wound dressing was
proposed. The inner layer (Hm-PNn) was a hybrid
hydrogel prepared by N-isopropylacrylamide and chitosan-N-2-hydroxypropyl trimethylammonium chloride (HACC), and
the outer layer (PVAo-PAmp) was prepared by
polyvinyl alcohols and acrylamide. The two hydrogel layers of the
bilayer model were covalently connected with excellent interfacial
strength by photoinduced electron/energy transfer-reversible addition-fragmentation
chain transfer (PET-RAFT) polymerization. The outer layer exposed
to the ambient environment exhibited good stretchability and toughness,
while the inner-layer hydrogel adhered to the skin exhibited excellent
softness, antibacterial activity, thermoresponsivity, and biocompatibility.
In particular, the inner layer of a hydrogel demonstrated excellent
antibacterial capability toward both Staphylococcus
aureus as Gram-positive bacteria and Escherichia coli as Gram-negative bacteria. Cell
cytotoxicity showed that the cell viability of all Hm-PNn layer hydrogels exceeds 80%, confirming that the hydrogels
bear excellent biocompatibility. In vivo experimental results indicated
that the Hm-PNn/PVAo-PAmp bilayer hydrogel has a significant effect on the acceleration of
wound healing, which was demonstrated in a full-thickness skin defect
model showing improved collagen disposition and granulation tissue
thickness. With these results, the established multifunctional bilayer
hydrogel exhibits potential as an excellent wound dressing for wound
healing applications, especially for open and infected traumas.
To increase the applicability of a rotor−stator reactor (RSR) in gas−liquid mass transfer processes, the effective mass transfer area (a e ) and the local gas-side mass transfer coefficient (k G ) in the RSR were measured by employing a NaOH solution to absorb CO 2 and SO 2 , where gas radial velocity is required to be large enough to ignore the gas-side mass transfer resistance in determination of a e . The effects of operating conditions and stator rings on these mass transfer parameters were investigated. The experimental results showed that a e and k G in the RSR with stator rings were higher than those in the RSR without stator rings by 17−30 and 1−9%, respectively. a e in the RSR with stator rings was 3.4% lower than that in a rotating packed bed, but k G in such RSR was higher than that in the rotating packed bed by 78.6%, suggesting that the RSR has great potential for industrial applications in the processes controlled by gas-side mass transfer.
Oxygen is a harmful substance in many processes because it can bring out corrosion and oxidation of food. This study aimed to enhance the removal of dissolved oxygen (DO) from water by employing a novel rotor–stator reactor (RSR). The effectiveness of the nitrogen stripping coupled with vacuum degassing technique for the removal of DO from water in the RSR was investigated. The deoxygenation efficiency (η) and the mass transfer coefficient (KLa) were determined under various operating conditions for the rotational speed, liquid volumetric flow rate, gas volumetric flow rate, and vacuum degree. The nitrogen stripping coupled with vacuum degassing technique achieved values for η and KLa of 97.34% and 0.0882 s−1, respectively, which are much higher than those achieved with the vacuum degassing technique alone (η = 89.95% and KLa = 0.0585 s−1). A correlation to predict the KLa was established and the predicted KLa values were in agreement with the experimental values, with deviations generally within 20%. The results indicate that RSR is a promising deaerator thanks to its intensification of gas–liquid contact.
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