Cellular Uptake of Covalent Poly(allylamine hydrochloride) Microcapsules and Its Influences on Cell Functions

Polyelectrolyte microcapsules have been widely used in biomedical field as novel drug delivery carriers and diagnosis probes for diseases.However, biological effect such as internalization process and influence on cell functions, which are of paramount importance for intracellular drug delivery, is still not fully addressed. This study is focused on the mechanism of the cellular uptake of microcapsules and its influences on the functions and toxicity of human smooth muscle cells (SMCs). The covalently assembled microcapsules with poly(allylamine hydrochloride) and glutaraldehyde as building blocks were prepared via LbL assembly on spherical dextran sulfate-doped CaCO3 template, followed by removal of the template.The microcapsules were easily ingested by SMCs mainly through macropinosis and caveolae-mediated endocytosis pathways. No exocytosis was observed. The capsules mainly dispersed in cytoplasm without colocalization in early endosomes and cell nucleus within 48 h culturein vitro. The results of gene chip revealed that 886 genes were down-regulated and 758 genes were up-regulated more than 2 folds after the cells were exposed to microcapsules, suggesting substantial and profound alternation of phenotypes and functions. Influences of the capsule uptake on cell toxicity and functions were then studied in terms of cell viability, cytoskeleton organization, cell cycle, cell adhesion and migration. Although uptake of the microcapsules caused slightly decrease of cell viability, it did cause significant alternation of cytoskeleton organization and cell cycle. The cell adhesion and migration ability were largely impaired too, demonstrating again the comprehensive impacts of capsule uptake on cell functions. Bing Wang#, Yuying Zhang#, Zhengwei Mao, Changyou Gao*. Cellular Uptake of Covalent Poly(allylamine hydrochloride) Microcapsules and Its Influences on Cell Functions, Macromolecular Bioscience, 2012, doi: 10.1002/mabi. 201200182.

Encapsulation of Photosensitizer into Multilayer Microcapsules by Combination of Spontaneous Deposition and Heat-induced

The poly(diallyldimethylammonium chloride)(PDADMAC)/poly(styrene sulfonate) (PSS) microcapsules assembled by layer-by-layer on PSS-doped CaCO3 particles were used to load photosensitizer methylene blue (MB) by combination of spontaneous deposition and heat-induced shrinkage. After annealing at 80 oCfor 30 min, the capsules shrink dramatically from 6.9±0.3 µm to 3.1±0.5 µm, accompanied with wall thickness increase. Incubation of MB in the capsule suspension following with annealing resulted in MB-loaded capsules with a concentration of 22 mg/mL, which was 1000 times higher than that of the feeding concentration. Although about 1/3 MB was released rapidly from the capsules in phosphate buffered saline, the remained MB were stably retained for long time, which were then protected by capsule wall against reductive enzyme and kept their photodynamic activity. The viability of HeLa cells incubated with MB-loaded capsules decreased sharply from ~75% (dark cytotoxicity) to ~20% after irradiation with a laser at 671 nm and 60 J/cm2 for 75 s.   Yuanyuan Han, Jing Bu, Yuying Zhang, Weijun Tong*, Changyou Gao*.Encapsulation of Photosensitizer into Multilayer Microcapsules by Combination of Spontaneous Deposition and Heat-induced Shrinkage for Photodynamic Therapy, Macromolecular Bioscience, 2012, doi: 10.1002/mabi.201200191. Download Pdf

Uptake of hydrogel particles with different stiffness and its influence on HepG2 cell functions

  The interactions between colloidal particles and cells are of paramount importance for understanding the potential safety issue of the particles, which in turn provide the design principles of various carriers for biomedical applications. In this study, the influence of particle stiffness on cellular uptake and cell functions are elucidated. Four types of poly(2-hydroxyethyl methacrylate) (HEMA) hydrogel particles with different amounts of crosslinking agent, N,N′-methylene-bis-acrylamide (BIS), and thereby compressive modulus (from 15–156 kPa) were synthesized by an emulsion–precipitation polymerization. All of the particles had a diameter of 800–1000 nm in water. Although the softer particles were slightly swollen in the cell culture medium, the particle sizes were still similar. Adsorption of proteins (35 mg g−1particles) occurred on all the particles, leading to a change of zeta potential from −20 mV (in water) to −5 mV (in serum containing medium). However, the particle size and surface charge property were not significantly changed. The softer particles were internalized by HepG2 cells at a faster rate and larger amount than the stiffer particles. Cellular uptake mechanisms were clarified by the addition of inhibitors to specific endocytosis pathways. The influence of the particle uptake on cell toxicity and functions were then studied in terms of cell viability, morphology and cytoskeleton organization, and cell adhesion. Uptake of all types of the particles did not cause an apparent decrease of cell viability and alteration of cell morphology, but changed the cytoskeleton organization to some extent. The cell adhesion ability was significantly affected, especially after uptake of the stiffer particles.   Weijun Liu, Xiangyan Zhou, Zhengwei Mao, Dahai Yu, Bing Wang and Changyou Gao Soft Matter, 2012, Advance Article, DOI: 10.1039/C2SM26001H First published on the web 02 Aug 2012 

Decomposition-Assembly of Tetraphenylethylene Nanoparticles With Uniform Size and Aggregation-Induced Emission property

Tetraphenylethylene (TPE) substituted poly(allylamine hydrochloride) (PAH-g-TPE) is synthesized by a Schiff base reaction between PAH and tetraphenylethylene carboxaldehyde (TPE-CHO). PAH-g-TPE forms micelles in water at pH 6, which are further transformed into pure TPE-CHO nanoparticles (NPs) with a diameter of ~300 nm after incubation in a solution of low pH value. In contrast, only amorphous precipitates are obtained when TPE-CHO methanol solution is incubated in water. The aggregation-induced emission feature of the TPE molecule is completely retained in the TPE NPs, which can be internalized into cells and show blue fluorescence. Formation mechanism of the TPE NPs is proposed by taking into account the guidance effect of linear and charged PAH molecules, and the propeller-stacking manner between the TPE-CHO molecules. Tianxiang Wang , Yunbo Cai , Zhipeng Wang , Erjia Guan , Dahai Yu , Anjun Qin*, Jingzhi Sun , Ben Zhong Tang, Changyou Gao*.Decomposition-Assembly of Tetraphenylethylene Nanoparticles With Uniform Size and Aggregation-Induced Emission property, Macromolecular Rapid Communications, 2012, DOI: 10.1002/marc.201200324. Download PDF

Layer-by-layer assembly of microcapsules and their biomedical applications

  Nanoengineered multifunctional capsules with tailored structures and properties are of particular interest due to their multifunctions and potential applications as new colloidal structures in diverse fields. Among the available fabrication methods, the layer-by-layer (LbL) assembly of multilayer films onto colloidal particles followed by selective template removal has attracted extensive attention due to its advantages of precise control over the size, shape, composition, wall thickness and functions of the obtained capsules. The past decade has witnessed a rapid increase of research concerning the new fabrication strategies, functionalization and applications of this kind of capsules, particularly in the biomedical fields such as drug delivery, biosensors and bioreactors.   In this critical review, the very recent progress of the multilayer capsules is summarized. First, the advances in assembly of capsules by the LbL technique are introduced with focus on tailoring the properties of hydrogen-bonded multilayer capsules by cross-linking, and fabrication of capsules based on covalent bonding and bio-specific interactions. Then the fabrication strategies which can speed up capsule fabrication are reviewed. In the following sections, the multi-compartmental capsules and the capsules that can transform their shape under stimulus are presented. Finally, the biomedical applications of multilayer capsules with particular emphasis on drug carriers, biosensors and bioreactors are described (306 references).   Weijun Tong, Xiaoxue Song, Changyou Gao*.Layer-by-Layer Assembly of Microcapsules and Their Biomedical Applications, Chemical Society Reviews, 2012, DOI: 10.1039/c2cs35088b. Download PDF

Group Alumni Meeting Was Successfully Held

    The first group alumni meeting was held on May 31, 2012, and several former group members were invited to come back to Zhejiang University for the communication and experience sharing with juniors. The meeting was chaired by Prof. Changyou Gao, and started with a party atmosphere. Prof. Jianjun Guan (Assistant Professor, Ohio State University, USA), Prof. Yabin Zhu (Professor, Ningbo University), Prof. Jie Feng (Associate Professor, Zhejiang University of Technology), Dr. Yi Hong (Research Assistant Professor, University of Pittsburgh), Dr. Xingyu Liu (setting up a high-technology company, Hangzhou), Dr. Xiaohong Hu (Jinling Institute of Technology), Dr. Feng Wang (Shanghai Normal University), Dr. Jie Zhou (Jushi Group CO., LTD), Dr. Yi Zhu (Jushi Group CO., LTD) and Yuan Qiu (Ph.D candidate in CIC biomaGUNE, Spain) detailed their own academic and work experiences, and answered the juniors’ questions at the end of the meeting.                                                                     

Group Members Attended 9th World Biomaterials Congress

9th World Biomaterials Congress was held in Chengdu, China from June 1 to June 5, 2012. Prof. Changyou Gao, Prof. Lie Ma, Associate Prof. Weijun Tong, Associate Prof. Zhengwei Mao and students including Tanchen Ren, Xiangyan Zhou, Feifei Li, Bo Li, Bing Wang, Yang Zhu, Dongming Xing, Chen Ye, Bing Zhang and Jun Deng attended the conference. As a member of the International Scientific Program Committee and a member of the Local Organization Committee, Prof. Changyou Gao organized the session of “Functional cell scaffolds combined with protein and gene”, co-chaired the session of “Layer-by-layer built biomaterials: 1-, 2- and 3D nanoassembly”and made an invited keynote speak on the topic of “Gene activated scaffolds for in vivo therapy of full thickness skin loss with enhanced angiogenesis”, which was highly appraised and widely acknowledged by worldwide colleagues. In addition, Prof. Lie Ma gave a lecture on “TGF-beta1 activated PLGA/Fibrin Gel/MSCs hybrids for the restoration of full thickness cartilage defects”, Associate  Prof. Weijun Tong reported work of “High efficient loading and controlled release of drugs by combination of spontaneous deposition and heat-induced shrinkage of multilayer capsules”, Associate Prof. Zhengwei Mao made a speech on “Cellular internalization of metal oxide nanoparticles and their influences on cell functions”. Extensive research works on preparation of colloid particles, gradient surfaces and functional scaffolds, cell behaviors including cellular uptake, migration and differentiation, as well as tissue defects restoration were presented by students. Through active participation during the conference, our group deepened collaboration and communication with Chinese and foreign colleagues, extended awareness and influence among the fields of biomaterials, tissue engineering and regenerative medicine. The theme for this congress is “Innovative Biomaterials and Crossing Frontiers in Biomaterials and Regenerative Medicine”. Researchers from biomaterials societies of USA, European countries, Canada, Japan, Australia, Korea, India, Latin-America, South Africa, Chinese Taipei and China focused on biomaterials, tissue engineering and regenerative medicine intensively discussed in 84 symposia, 5 workshops and 3 forums. State-of-the-art research works, cutting-edge technological advances and significant progresses in clinical applications were extensively addressed, which made the congress an interdisciplinary forum for scientists, researchers, clinicians, industrialists and administrators. For more information of the congress, please visit www.wbc2012.com.  

Two day's tour in Quzhou City

Two day's tour in Quzhou City

Two day's tour in Quzhou City

IFBM2012-3rd Circular

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Shape Deformation and Recovery of Multilayer Microcapsules after Being Squeezed through a Microchannel

  The deformation and recovery behaviors of multilayer microcapsules were investigated after being forced to flow through a microchannel. The microchannel device with a constriction (5.7 μm in depth) in the middle was designed, and the multilayer microcapsules with different size and layer thickness (and thereby different mechanical strength) were used. Deformation in the microchannel was observed for all the capsules with a size larger than the constriction height, and its extent was mainly governed by the difference between capsule size and constriction height. The squeezed microcapsules could recover their original spherical shape when the deformation extent was smaller than 16%, whereas permanent physical deformation took place when the deformation extent was larger than 34%. The capsules filled with polyelectrolytes could greatly enhance their shape recovery ability due to the higher osmotic pressure in the capsule interior and could well maintain the preloaded low-molecular-weight dyes regardless of the squeezing.   Reference：Shupeng She,Chunxiu Xu, Xuefeng Ying, Weijun Tong*, Changyou Gao*.Shape Deformation and Recovery of Multilayer Microcapsules after Being Squeezed through a Microchannel, Langmuir, 2012, DOI: 10.1021/la3003299. Download PDF  

Modulating the Structure and Properties of PSS/PDADMAC Multilayers with Concentrated Salt Solutions

The salt treatment can easily change the structure and physiochemical properties of the PSS/PDADMACmultilayers, resulting in thinfilms with various features. Because the polyanion/polycation stoichiometry in bulk multilayers is observed to be 1:1 or at least close to this value, multilayer 3 M can be regarded as the bulk film because of the roughly equal amounts of PSS and PDADMAC. As a result of the better compensation (5% counterions), the largest cross-linking density is expected among others, leading to the smallest swelling behavior in water. For the thin films with larger numbers of uncompensated for polyions such as multilayers 1 and 5 M, a swollen, hydrated structure is formed. Moreover, because the slight mass loss does not obviously change the multilayer structure, multilayers 0, 1, and 2M can basically maintain their initial physicochemical structure (a PDADMAC-dominated surface). By contrast, the massive loss of polyelectrolytes completely destroys the layered structure of multilayers 4 and 5 M, leading to a surface chemistry reversal. In such a case, the structure is not composed of multilayers any longer. The obtained polymer thin films with various structures and properties are expected to find diverse applications in the fields of biomaterials, medicine, and nanotechnology.   Reference：Lulu Han, Zhengwei Mao, He Wuliyasu, Jindan Wu, Xiao Gong, Yuguang Yang, and Changyou Gao*, Modulating the Structure and Properties of Poly(sodium 4-styrenesulfonate)/Poly(diallyldimethylammonium chloride) Multilayers with Concentrated Salt Solutions. Langmuir, 2012, 28: 193-199. Download PDF    

BSA nanoparticles modified with multilayers and aptamers for pH-responsive and targeted anti-cancer drug delivery

The widely used bovine serum albumin (BSA) nanoparticles (NPs) were modified with poly(allylamine hydrochloride) (PAH)/sodium poly(4-styrene sulfonate) (PSS) multilayers and aptamers to improve their suspension stability and targeting ability. For this to occur, a PAH-g-poly(ethylene glycol) (PAH-g-PEG–COOH) layer was further adsorbed onto the (PAH/PSS)2 multilayer-coated BSA NPs and used to covalently bond the aptamer AS1411, which is known to specifically bind the over-expressed nucleolin on cancer cell membranes. The PEGylated multilayer-coated BSA NPs showed good suspension stability in diverse media, in particular in a serum containing medium. By a mechanism of spontaneous deposition, doxorubicin (DOX) was effectively loaded into the pre-formed BSA NPs with both good encapsulation efficiency (98.6%) and loading percentage (9%). The loaded drug showed a pH-dependent release behaviour, i.e. faster at pH 5.5 than at pH 7.4. The multilayer coating did not significantly influence either both drug loading or release. In vitro cell culture demonstrated that the as-prepared BSA NPs could be specifically delivered to liver cancer cells, leading to higher cellular uptake and cytotoxicity. Reference：Lili Xie, Weijun Tong,* Dahai Yu, Jianquan Xu, Jun Li, and Changyou Gao*, Bovine serum albumin nanoparticles modified with multilayers and aptamers for pH-responsive and targeted anti-cancer drug delivery. J. Mater. Chem., 2012, DOI: 10.1039/c2jm16831f.