High moisture permeability, excellent
mechanical properties in
a wet state, high water-holding capability, and high exudate absorption
make bacterial nanocellulose (BNC) a favorable candidate for biomedical
device production, especially wound dressings. The lack of antibacterial
activity and healing-promoting ability are the main drawbacks that
limit its wide application. Pullulan (Pul) is a nontoxic polymer that
can promote wound healing. Zinc oxide nanoparticles (ZnO-NPs) are
well-known as a safe antibacterial agent. In this study, aminoalkylsilane
was chemically grafted on a BNC membrane (A-g-BNC)
and used as a bridge to combine BNC with Pul-ZnO-NPs hybrid electrospun
nanofibers. FTIR results confirmed the successful production of A-g-BNC/Pul-ZnO. The obtained dressing demonstrated blood
clotting performance better than that of BNC. The dressing showed
an ability to release ZnO, and its antibacterial activity was up to
5 log values higher than that of BNC. The cytotoxicity of the dressing
toward L929 fibroblast cells clearly showed safety due to the proliferation
of fibroblast cells. The animal test in a rat model indicated faster
healing and re-epithelialization, small blood vessel formation, and
collagen synthesis in the wounds covered by A-g-BNC/Pul-ZnO.
The new functional dressing, fabricated with a cost-effective and
easy method, not only showed excellent antibacterial activity but
could also accelerate wound healing.
Bacterial
nanocellulose (BNC) is a promising material for small-caliber
artificial blood vessels, although promoting its anticoagulant properties
with more rapid endothelialization would improve long-term patency.
Silk fibroin nanoparticles (SFNP) were introduced into the luminal
wall surface of BNC conduits both with and without heparin (Hep) through
pressurization followed by fixation. Hep was introduced in two ways:
(1) embedded within SF nanoparticles to form SF-HepNPs for construction
of the BNC-SF-HepNP conduit and (2) chemically grafted onto BNC and
BNC-SFNP to form BNC-Hep and BNC-SFNP-Hep conduits. Fourier transform
infrared spectroscopy confirmed the formation of SF-HepNPs, although
they did not incorporate into the fibrillar network due to their large
size. Hep was successfully grafted onto BNC and BNC-SFNP, verified
by toluidine blue staining. The hemocompatibility and cytocompatibility
of the five samples (BNC, BNC-SFNP, BNC-SF-HepNP, BNC-Hep, and BNC-SFNP-Hep
conduits) were compared in vitro. The heparinized
BNC-Hep and BNC-SFNP-Hep conduits improved the anticoagulant properties,
and BNC-SFNP-Hep promoted human umbilical vein endothelial cell proliferation
but also controlled excessive human arterial smooth muscle cell proliferation,
assisting rapid endothelialization and improving lumen patency. No
significant inflammatory reaction or material degradation was observed
after subcutaneous implantation for 4 weeks. Autogenous tissues were
observed around the conduits, and cells infiltrated into the edges
of all samples, the BNC-SFNP conduit causing the deepest infiltration,
providing an appropriate microenvironment for angiogenesis when used
in small-caliber blood vessel applications. Few inflammatory cells
were found around the BNC-Hep and BNC-SFNP-Hep conduits. Thus, the
anticoagulant properties of the BNC-SFNP-Hep conduit and its stimulation
of endothelialization suggest that it has great potential in clinical
applications as a small-caliber artificial blood vessel.
Alginate (Alg) and bacterial nanocellulose (BNC) have exhibited great potential in biomedical applications, especially wound dressing. Non-toxicity and a moisture-maintaining nature are common features making them favorable for functional dressing fabrication. BNC is a natural biopolymer that promotes major advances to the current and future biomedical materials, especially in a flat or tubular membrane form with excellent mechanical strength at hydrated state. The main drawback limiting wide applications of both BNC and Alg is the lack of antibacterial activity, furthermore, the inherent poor mechanical property of Alg leads to the requirement of a secondary dressing in clinical treatment. To fabricate composite dressings with antibacterial activity and better mechanical properties, sodium alginate was efficiently incorporated into the BNC matrix using a time-saving vacuum suction method followed by cross-linking through immersion in separate solutions of six cations (manganese, cobalt, copper, zinc, silver, and cerium). The results showed the fabricated composites had not only pH-responsive antibacterial activities but also improved mechanical properties, which are capable of acting as smart dressings. All composites showed non-toxicity toward fibroblast cells. Rat model evaluation showed the skin wounds covered by the dressings healed faster than by BNC.
Taking the fashion mnist data set proposed by zalando research team in 2017 as the object, this paper constructed a "shallow" neural network, whose test result accuracy reached 0.98, and then took the mnist data set as the test object to display the test results. when constructing the model, the loss function, activation function, gradient optimizer, overfitting and learning rate were explained, among which the gradient optimizer and overfitting had the greatest influence on the overall model accuracy.
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