| Drug delivery systems(DDS)play an important role in modern therapy.In vivo,they are mainly used in the treatment of cancer,diabetes.In vitro,they are mainly applied for the curation and protection of cutaneous wounds,such as diabetic foot ulcer,bedsore and burn wounds.However,traditional DDS have disadvantages of failure and early release of drugs before reaching the target location,resulting in the lower healing efficiency.Smart drug delivery system could make up for these demerits.In the treatment and care of diabetic foot ulcer and bedsore,it is difficult for the traditional wound dressings to achieve sustained release on demand,resulting in the frequent change of wound dressing that might hinder the heal of wounds.On the contrary,wound dressings that release drug on demand have a significant care and healing effect on such chronic wounds.However,the current drug-loaded dressings could only achieve drug sustained release rather than release on demand.Additionally,the biocompatibility,air permeability as well as the extrudate transmission ability need to be improved.Therefore,in this work,the thermo-sensitive polymer P(NIPAM-ABP)and biocompatible polymer gelatin are employed to prepare a thermo-regulated drug controlled-release nanofiber system.In the meantime,in order to prevent the premature release and destruction of the drug,mesoporous silica nanoparticles(MSNs)were used as the drug carrier and to be embedded in gelatin.First,the modified St?ber method(template replication method)was used to prepare mesoporous silica nanoparticles.The method is illustrated as followed.The surfactant cetyl trimethyl ammonium bromide(CTAB)is used to form micelles in deionized water,and then tetra-orthosilicate(TEOS)is added in dropwise to be hydrolyzed under the catalysis of ammonia,and self-assemble along the micelles in situ to form nanoparticles.Then the template is washed away in ethanol to obtain silica nanoparticles with a mesoporous structure.After then,the structure of MSNs is characterized via scanning electron microscope(SEM),transmission electron microscope(TEM),BET and Zeta potential,Fourier transform infrared spectroscopy(FTIR)and small angle X-Ray diffraction(SAXRD).It is shown that the MSNs have favorable dispersibility and are negative charged on the surface,which is conducive to their dispersion in the solution and the adsorption of small molecules.The MSNs are uniform in size,with an average size of 89.46nm.There are interconnected worm-like holes on the surface and inside.The average size of the mesopores is6.52nm,and the specific size is 853.31m~2/g.After calculations,the adsorption rate of rhodamine b(RHB)is up to 57%.Second,in order to improve the water stability and mechanical properties of the raw material gelatin,green cross-linking agent genipin is chosen for cross-linking.The results showed that 5wt.%genipin had a favorable crosslinking effect.The water stability and mechanical properties of nanofiber membranes have been significantly improved.Reading from the testing results,the tensile elongation at break is 6.5 times of that non-crosslinked one,and the work at break is 7.6 times of the non-crosslinked one.Hence.It is indicated that the tenacity of the nanofiber membranes is enhanced by the crosslinker.In addition,after the characterization of FTIR and XRD,it is shown that the secondary structure has changed,with the hydrogen bonds in the molecule rearranged and the amorphous region increased,resulting in the increment of membranes’tenacity.Third,bicomponent side-by-side electrospinning nanofiber mats are prepared.After exploration,it was found that when setting the extrusion speeds of P(NIPAM-ABP)and gelatin as1m L/hr and 0.8m L/hr,a better side-by-side structure could be produced.Then,10%MSNs are embedded onto gelatin to prepare drug-loaded bicomponent side-by-side fibers.The fibers are characterized by SEM,TEM,AFM,FTIR,XRD and EDS etc.for the analysis of structures and components.Lastly,the thermo-responsiveness and application properties of bicomponent side-by-side nanofibers are characterized.The results show that the fiber is responsive to temperature.It bends above the lower critical solution temperature(LCST)and stretch below the LCST,resulting in the deformation of fiber mats.Triggered by the temperature,the fiber mats contract above LCST and swell or stretch under LCST.It is shown that the release rate of the fiber mats above LCST is 7.7times of that below LCST and this process is reversible.In addition,it is tested that the fiber mats can absorb 7.7-14.5 times water based on its own weight,exhibiting the ability to absorb and transfer liquid.In summary,this work prepares bicomponent side-by-side nanofiber mat via electrospinning,of which drug release rate could be regulated by temperature.After then,structure,chemical properties and application properties are characterized and explored.The results exhibit that the drug release rate of the bicomponent side-by-side fiber mats could be controlled and regulated and the regulating process is reversible.At the same time,after testing the additional properties,including water uptake rate and air permeability,it is found that the as-made bicomponent side-by-side fiber mat could be potentially used as the functional layer(for drug loading and drug releasing)in the wound dressings. |
