The Fabrication Of Nanocarriers Loaded With Growth Factors And Their Loading/Releasing Performances

In protein therapy,researchers often deliver exogenous protein drugs into the body to realize the treatment of protein deletion or reduction caused by various diseases.In addition,tissue defects caused by disease or other reasons also require various therapeutic molecules(especially protein molecules)to promote tissue regeneration in the body.Therefore,how to effectively ensure that the protein drug enters the body while the drug activity is not affected by the in vivo and in vitro environment is still a big challenge.At present,researchers often use various material carriers to achieve effective delivery of drugs in vivo.Among them,biomineral materials have been widely studied in protein drug carriers due to their excellent biocompatibility and controllable morphological properties.Several typical mineral supports include mesoporous silica,vaterite,hydroxyapatite,carbon nanotubes,etc.However,these materials still have many problems in protein drug delivery.For instance,drug delivery systems often require large drug doses and long half-lives,leading to a big challenge to stabilize the drug protein and achieve long-term release in the body.In addition,the requirement for the biocompatibility of the carriers will also be elevated.During the process of biomimetic mineralization,biological macromolecules often have a significant impact on the nucleation,morphology,crystal form and other characteristics of minerals.Based on the biomimetic mineralization mechanism,we developed a simple synthesis,which directly utilizes the co-mineralization of protein drugs and mineral materials to produce a mineral carrier that can effectively load and release protein drugs.First,we adjusted the loading and releasing characteristics of protein drugs by changing different mineralization conditions,and achieved high loading and long-term release of protein drugs.Subsequently,we further optimized the mineralization conditions and used a variety of proteins and growth factors to synthesize the carriers,which confirmed the universality of the method.Finally,the in vivo feasibility of this method was confirmed by the in vivo payload release of specific osteogenesis-related growth factors.The main findings obtained are as follows:1.Inspired by the biomimetic mineralization mechanism,this paper uses the following methods to solve the problem of the low protein drug loading capacity of minerals.Since protein can inhibit the crystallization process of minerals,we directly uses protein drugs as mineral crystallization inhibitors to synthetic amorphous mineral material in a controlled environment.Compared with the crystalline phase,amorphous minerals have higher surface energy and can attract more proteins.In addition,since amorphous minerals do not have specific crystal planes,proteins can be uniformly distributed in amorphous minerals without being restricted by the adsorption of specific crystal planes.Since no other polyelectrolytes for stabilizing amorphous are added in the reaction,the side effects of other polyelectrolytes are also avoided.We synthesized amorphous carbonated calcium phosphate(ACCP)nanoparticles that efficiently load and release drug proteins without adding other organic additives in a controlled mineralization environment.High loading amount(up to 31.5 wt% for Cytochrome C,33.14 wt% for bovine serum albumin,and 32.33 wt% for insulin like growth factor-1(IGF-1);due to the high surface energy of the amorphous minerals)and long-acting release(due to the homogeneous distribution of the proteins)can be achieved simultaneously for the ACCP-based protein carriers.As a proof of the well-retained bioactivity of the drug proteins,we explore the performance of ACCP NPs loaded with IGF-1 in bone reconstruction.The IGF-1 loaded ACCP NPs show excellent biocompatibility and promising osteogenesis ability both in vitro and in vivo.As there are abundant functional groups in the proteins,many of the drug proteins should be able to stabilize amorphous minerals temporarily.Therefore,it is believed that the strategy,i.e.,stabilizing unstable amorphous mineral carriers directly with drug proteins,can be easily extended to other minerals and proteins,which can be used for various biomedical applications.2.Based on the controllability and excellent biocompatibility of biominerals,we are further optimizing the mineralization conditions to prepare a calcium phosphate carrier that can load protein drugs efficiently.The synthesis is simpler and more convenient,and the protein activity is effectively protected.In addition,we used this method to load several other growth factors(insulin-like growth factor-1,epidermal growth factor,vascular endothelial growth factor and bone morphogenetic protein-2),all of which achieved the effective loading of growth factors,proving that the certain universality of this method.Finally,through the in vivo and in vitro biological experiments,we confirmed that the carrier loaded with IGF-1 can effectively promote bone tissue regeneration and proved that the bioactivity of the growth factor is effectively preserved.This method is simple and stable,and provides a potential way for protein therapy.