Freeze-drying is a promising method for a long-term storage of human platelets.The moisture sorption characteristics of freeze-dried human platelets(FDHPs) were studied in this paper.The moisture sorption isotherms of...Freeze-drying is a promising method for a long-term storage of human platelets.The moisture sorption characteristics of freeze-dried human platelets(FDHPs) were studied in this paper.The moisture sorption isotherms of FDHPs and freeze-dried lyophilization buffer(FDLB) were measured at 4,25,and 37°C.The experimental data were fitted to Brunauer-Emmett-Teller(BET) and Guggenheim-Anderson-de Boer(GAB) equations.There were no sig-nificant statistical differences(P>0.05) between the sorption characteristics of FDHPs and FDLB at 4 and 25°C,while FDHPs absorbed more water at 37°C.The net isosteric heat of sorption was derived.The heat for FDHPs showed an abnormal negative value at low moisture contents when 25 and 37°C data were used.Dynamic sorption experiments were carried out at 25°C with environmental water activity controlled at 0.75,0.85,and 0.90.The moisture diffusion coefficient was fitted to be 8.24×10 -12 m 2 /s when experimental data at initial time were used.These results would be helpful in choosing prehydration and storage condition for FDHPs.展开更多
Pre-freezing is an important stage in freeze-drying processes.For the lyophilization of a cell,freezing not only plays a role for primary dehydration,but it also determines the amount of residual(intracellular or extr...Pre-freezing is an important stage in freeze-drying processes.For the lyophilization of a cell,freezing not only plays a role for primary dehydration,but it also determines the amount of residual(intracellular or extracellular)water,which in turn can influence the solution properties and the choice of operation parameters.The freezing of human platelets in lyoprotectant solution is theoretically investigated here.A two-parameter model and an Arrhenius expression are used to describe cell membrane permeability and its temperature dependency.It is assumed that the intracellular solution is composed of four components:sodium chloride,trehalose,serum protein and water,while the extracellular solution consists of three components.Non-ideal solution behaviors are predicted using measured data.The concentration of maximally freeze-concentrated solution is estimated on the basis of an assumption of solute hydration.The impacts of lyoprotectant composition and extracellular sub-cooling on intracellular supercooling and residual water content in the cell are analyzed.The values of activation energy of hydraulic permeability at low temperatures are tested to study their impact on the critical cooling rate.As the mass fraction extracellular lyoprotectant(trehalose+bovineserum albumin)increases from 5 wt%to 20 wt%,the intracellular water content at the end of freezing does not change,but the intracellular solution undergoes much higher super-cooling degree.Increasing the mass ratio of trehalose to bovine serum albumin does not change the intracellular water content,but can mitigate intracellular super-cooling.While 0.05 mol/kg trehalose is loaded into platelet,the total quantity of residual water at the end of freezing may raise by 4.93%.The inclusion of dimethyl sulfoxide(Me2SO)in protectant may bring negative impacts to the drying stage by increasing the residual water content and lowering the drying temperature.展开更多
Human platelets aggregate at sites of blood vessel damage in response to a rise in their cytosolic calcium concentration.Controlling these cytosolic calcium rises would provide a method to inhibit platelet activation ...Human platelets aggregate at sites of blood vessel damage in response to a rise in their cytosolic calcium concentration.Controlling these cytosolic calcium rises would provide a method to inhibit platelet activation and prevent the unwanted blood clots that causes heart attack and strokes.Previously we have predicted that calcium accumulation within the lumen of an infolded portion of the platelet plasma membrane called the open canalicular system(OCS)is essential for maintaining this cytosolic calcium rise.Due to its nanometer dimensions of the OCS,it has been difficult to measure or interfere with the predicted luminal calcium accumulation.Here we utilise iron oxide magnetic nanoparticles coated with the known calcium chelator,citrate,to create calcium-binding nanoparticles.These were used to assess whether an OCS calcium store plays a role in controlling the dynamics of human platelet activation and aggregation.We demonstrate that citrate-coated nanoparticles are rapidly and selectively uptaken into the OCS of activated human platelets,where they act to buffer the accumulation of calcium there.Treatment with these calcium-binding nanoparticles reduced thrombin-evoked cytosolic calcium rises,and slowed platelet aggregation and clot retraction in human platelets.In contrast,nanoparticles that cannot bind calcium have no effect.This study demonstrates that the OCS acts as a key source of calcium for maintaining cytosolic calcium rises and accelerating platelet aggregation,and that calcium-binding nanoparticles targeted to the OCS could provide an anti-platelet therapy to treat patients at risk of suffering heart attacks or strokes.展开更多
基金Project supported by the Natural Science Foundation of Zhejiang Province,China(No.Y1090409)the Doctoral Fund of Ministry of Education of China(No.20070335145)
文摘Freeze-drying is a promising method for a long-term storage of human platelets.The moisture sorption characteristics of freeze-dried human platelets(FDHPs) were studied in this paper.The moisture sorption isotherms of FDHPs and freeze-dried lyophilization buffer(FDLB) were measured at 4,25,and 37°C.The experimental data were fitted to Brunauer-Emmett-Teller(BET) and Guggenheim-Anderson-de Boer(GAB) equations.There were no sig-nificant statistical differences(P>0.05) between the sorption characteristics of FDHPs and FDLB at 4 and 25°C,while FDHPs absorbed more water at 37°C.The net isosteric heat of sorption was derived.The heat for FDHPs showed an abnormal negative value at low moisture contents when 25 and 37°C data were used.Dynamic sorption experiments were carried out at 25°C with environmental water activity controlled at 0.75,0.85,and 0.90.The moisture diffusion coefficient was fitted to be 8.24×10 -12 m 2 /s when experimental data at initial time were used.These results would be helpful in choosing prehydration and storage condition for FDHPs.
基金supported by the National Natural Science Foundation of China[grant number 51876185]archaeological artifact protection technology project of Zhejiang Province grant number 2017008].
文摘Pre-freezing is an important stage in freeze-drying processes.For the lyophilization of a cell,freezing not only plays a role for primary dehydration,but it also determines the amount of residual(intracellular or extracellular)water,which in turn can influence the solution properties and the choice of operation parameters.The freezing of human platelets in lyoprotectant solution is theoretically investigated here.A two-parameter model and an Arrhenius expression are used to describe cell membrane permeability and its temperature dependency.It is assumed that the intracellular solution is composed of four components:sodium chloride,trehalose,serum protein and water,while the extracellular solution consists of three components.Non-ideal solution behaviors are predicted using measured data.The concentration of maximally freeze-concentrated solution is estimated on the basis of an assumption of solute hydration.The impacts of lyoprotectant composition and extracellular sub-cooling on intracellular supercooling and residual water content in the cell are analyzed.The values of activation energy of hydraulic permeability at low temperatures are tested to study their impact on the critical cooling rate.As the mass fraction extracellular lyoprotectant(trehalose+bovineserum albumin)increases from 5 wt%to 20 wt%,the intracellular water content at the end of freezing does not change,but the intracellular solution undergoes much higher super-cooling degree.Increasing the mass ratio of trehalose to bovine serum albumin does not change the intracellular water content,but can mitigate intracellular super-cooling.While 0.05 mol/kg trehalose is loaded into platelet,the total quantity of residual water at the end of freezing may raise by 4.93%.The inclusion of dimethyl sulfoxide(Me2SO)in protectant may bring negative impacts to the drying stage by increasing the residual water content and lowering the drying temperature.
基金Authors are deeply acknowledged to the Wellcome Trust for funding support(Seed Award in Science,Project grant no 207617/Z/17/Z).
文摘Human platelets aggregate at sites of blood vessel damage in response to a rise in their cytosolic calcium concentration.Controlling these cytosolic calcium rises would provide a method to inhibit platelet activation and prevent the unwanted blood clots that causes heart attack and strokes.Previously we have predicted that calcium accumulation within the lumen of an infolded portion of the platelet plasma membrane called the open canalicular system(OCS)is essential for maintaining this cytosolic calcium rise.Due to its nanometer dimensions of the OCS,it has been difficult to measure or interfere with the predicted luminal calcium accumulation.Here we utilise iron oxide magnetic nanoparticles coated with the known calcium chelator,citrate,to create calcium-binding nanoparticles.These were used to assess whether an OCS calcium store plays a role in controlling the dynamics of human platelet activation and aggregation.We demonstrate that citrate-coated nanoparticles are rapidly and selectively uptaken into the OCS of activated human platelets,where they act to buffer the accumulation of calcium there.Treatment with these calcium-binding nanoparticles reduced thrombin-evoked cytosolic calcium rises,and slowed platelet aggregation and clot retraction in human platelets.In contrast,nanoparticles that cannot bind calcium have no effect.This study demonstrates that the OCS acts as a key source of calcium for maintaining cytosolic calcium rises and accelerating platelet aggregation,and that calcium-binding nanoparticles targeted to the OCS could provide an anti-platelet therapy to treat patients at risk of suffering heart attacks or strokes.
