Screening of additives to reduce grain damage risk on unhairing by proteinase K

Enzymatic unhairing is a cleaner strategy for leather-making.It is a potential alternative to the traditional hairburning process.However,several shortcomings,such as uncontrolled enzymatic reaction,and risk of grain looseness and damage have restricted the broad application of enzymatic unhairing.In this work,metal ions and organic additives were screened for lessening the hydrolytic activity of proteinase K to collagen fiber.Then,the selected additives were applied to the enzymatic unhairing process for bovine hide.The results showed that a suitable concentration of metal ions(Cu(Ⅱ),Fe(Ⅲ)and Al(Ⅲ))and organic additives(salicylate,laurate,adipate,gallate and epicatechin(ECG))could diminish approximately 35% of the hydrolytic activity of proteinase K to collagen fibers.Then,the additives were applied for the bovine hide enzymatic unhairing process.Hydroxyproline determination in the unhairing float shows that applying additives could reduce collagen hydrolysis.The morphology results showed that the grain damage could be significantly reduced with the addition of the screened additives in the proteinase K enzymatic unhairing system,whereas the addition of ECG and gallate significantly slowed down the unhairing speed.This outcome provides new potential to reduce the risk of grain damage in enzymatic unhairing process.

RELEASE OF IBUPROFEN FROM PEG-PLLA ELECTROSPUN FIBERS CONTAINING POLY(ETHYLENE GLYCOL)-b-POLY(α-HYDROXY OCTANOIC ACID) AS AN ADDITIVE

Poly（a-hydroxy octanoic acid） was first used as an additive for the preparation of electrospun ultra-fine fibers of poly（ethylene glycol）-b-poly（L-lactide） （PEG-PLLA）. Ibuprofen was loaded in the electrospun ultra-fine fibers. The results from environmental scanning electron microscopy （ESEM）, wide angle X-ray diffraction （WAXD） and differential scanning calorimetry （DSC） demonstrated that ibuprofen could be perfectly entrapped in the fibers electrospun from PEG-PLLA using a-hydroxy octanoic acid or PEG-b-poly（a-hydroxy octanoic acid） （PEG-PHOA） as additives. Compared with electrospun PEG-PLLA fibers which entrapped 20 wt% ibuprofen, the PEG-PLLA electrospun fibers containing PEG-PHOA exhibited integral and robust after 1 week incubated in 37℃, pH 7.4 phosphate buffer solution with 10 μg/mL proteinase K. Compared with electrospun fibers without PEG-PHOA, the concentration ofproteinase K in release media had less effect on the release rate of ibuprofen. An unique release profile was found from PEG-PLLA fiber after the incorporation of PEG-PHOA. Enzyme degradation experiments demonstrated that PEG-PHOA but not a-hydroxy octanoic acid monomer was the crucial factor for integrity maintenance of the electrospun fibers, which may be due to the enzyme degradation tolerance property of the PEG-PHOA polymer additive.

MAGNOLOL ENTRAPPED ULTRA-FINE FIBROUS MATS ELECTROSPUN FROM POLY(ETHYLENE GLYCOL)-b-POLY(L-LACTIDE) AND IN VITRO RELEASE

Ultra-fine fibrous mats with magnolol entrapped have been prepared by electrospinning biodegradable copolymer poly（ethylene glycol） blocked poly（L-lactide）.Drug entrapment was perfect which was confirmed by scanning electron microscopy and differential scanning calorimetry.According to in vitro drug release investigation by high performance liquid chromatography,it was found that fibers with 10%,20%and 30%drug entrapped respect to polymer（mass ratio） presented dramatically different drug release behavior and degradation behavior under the effect of proteinase K.The reason may be that fibers with 10%drug entrapped was more easily affected by enzyme while,to some degree,magnolol in fibers with 20% and 30%entrapped prevented polymer from being degraded by enzyme.