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SUSTech Changfeng Wu’s group develops highly bright polymer dots for three-dimensional multicolor super-resolution imaging applications

Recently, a research team led by Professor Changfeng Wu from the Department of Biomedical Engineering at the Southern University of Science and Technology (SUSTech) developed a series of highly bright polymer dots probes. Through the functionalization of polymer dots probes and application in expansion microscopy, fine subcellular structures with a resolution of ≈ 30 nm can be resolved on a conventional fluorescent microscope. Their research, entitled “Expansion Microscopy with Multifunctional Polymer Dots,” was published in Advanced Materials, a top journal in the field of materials science.

 

 

Super-resolution optical imaging won the 2014 Nobel Prize in Chemistry for its ability to provide resolution below the diffraction limit. The current super-resolution technology mainly contains two categories, one of which relies on patterned illumination modulation and the other one based on single-molecule positioning. Expansion microscopy uses a completely different strategy that physically enlarges the samples to allow clear distinction of adjacent molecules that are originally within the diffraction limit. This method does not rely on a complex imaging system, and nanoscale resolution can be achieved on a common confocal microscope. However, the fluorescence brightness attenuation caused by chemical quenching and density dilution during sample preparation has long been a challenge for further applications.   

 

Changfeng Wu’s research group developed multifunctional polymer dots for application in multicolor expansion microscopy to address this issue. The fluorescence intensity of Pdots in ExM was up to 6 times higher than those achieved using commercially available Alexa dyes. The impressive brightness of the Pdots facilitated multicolor ExM, thereby enabling a variety of subcellular structures, such as mitochondria, clathrin-coated pits, and neuron synapses to be visualized on traditional fluorescent microscopes (Figure 1a-c). Furthermore, the research group combined polymer dots probes, expansion microscopy, and super-resolution optical fluctuation microscopy to achieve ultrahigh-resolution imaging of subcellular structures on a conventional wide-field microscope. As a result, this reflected the actual size of microtubules and the hollow membrane structure of mitochondria (Figure 1d-j). These findings highlight the immense potential of highly bright polymer dots for biological imaging.

Figure 1. Three-dimensional super-resolution expansion and optical fluctuation imaging of subcellular structures

 

The immunofluorescence staining of samples is tedious and time-consuming. To improve the efficiency of the project, Zhihe Liu, a postdoctoral fellow in the research group, designed an automatic cell immunostaining system (Figure 2). As a result, this could replace manual work for immunofluorescence staining experiments.

Figure 2. Automatic cell immunostaining system

 

Jie Liu, a doctoral student supported by the joint Ph.D. program between SUSTech and the Hong Kong Baptist University (HKBU), is the first author of this paper. SUSTech is the correspondence unit of this paper. The above research has been supported by the National Natural Science Foundation of China (NSFC), the National Key R&D Program of China, and the Shenzhen Science and Technology Innovation Commission. 

 

Paper link: https://doi.org/10.1002/adma.202007854

Department of Biomedical Engineering holds 5th Anniversary Achievement Exhibition

On May 22, 2021, the Department of Biomedical Engineering (BME) at the Southern University of Science and Technology (SUSTech) celebrated its 5th anniversary by holding an Achievement Exhibition.

The achievement exhibition was made accessible for both online and offline participation. Yusheng ZHAO, Acting Vice President of SUSTech and Dean of the SUSTech Academy for Advanced Interdisciplinary Studies, attended the event.

 

 

Yusheng ZHAO said that BME has developed rapidly in the past five years and has achieved remarkable results. He hopes that the department will continue to strengthen and grow in the future while also promoting the cross-integration of disciplines and innovation of advanced technology.  

Xingyu JIANG, Head of BME, expressed his gratitude to everyone who has helped and supported the development of BME over the past few years. He added that its success wouldn’t have been possible without the support of the leadership team at SUSTech, faculty members, students, and other volunteers that have assisted the department since its formation.

All 17 research groups of BME participated in the exhibition, attracting more than 100 experts, scholars, faculty members, and students within SUSTech to participate in the event.

SUSTech Kai Li’s team makes progress in type-I photosensitizers with tumor-associated macrophages polarizing activity

Recently, Kai Li’s laboratory at the Department of Biomedical Engineering of the Southern University of Science and Technology (SUSTech) has made significant experimental progress in tumor photodynamic immunotherapy. The research paper, titled “Acceptor Engineering for Optimized ROS Generation Facilitates Reprogramming Macrophages to M1 Phenotype in Photodynamic Immunotherapy” was published by Angewandte Chemie International Edition.

Reprogramming tumor‐associated macrophage cells by photodynamic therapy (PDT) is a promising approach to overcoming the suppression of tumor microenvironment for boosted immunotherapy. It remains unclear how the reactive oxygen species (ROS) generated from type I and II mechanisms relate to the macrophage polarization efficacy. Prof. Li’s team designed and synthesized three photosensitizers with varied ROS‐generating effectiveness.

Surprisingly, they discovered that the extracellular ROS generated from type I mechanisms are mainly responsible for reprogramming the macrophages from a pro‐tumor type (M2) to an anti‐tumor state (M1). In vivo experiments prove that the photosensitizer can produce effective suppression of the tumor growth, while the therapeutic outcome is eliminated with depleted macrophages. Overall, their strategy highlights the design guideline of macrophage‐activated photosensitizers.

Here were the key findings from their analysis:

1. Three donor-acceptor (D-A) structured AIEgen photosensitizers have been synthesized using the compound triphenylamine as the electron donor, and their ROS-generating efficiencies are adjusted by using acceptor units with varied electron deficiencies.

2. Using commercial photosensitizers, such as chlorin 6 (Ce6) and rose bengal (RB), they discover that the extracellular ROS generated from type I mechanism rather than type II mechanism plays a key role in reprogramming the macrophages to M1 phenotype. This is of high importance in in vivo anti-tumor applications, taking into account the lower oxygen dependence of type I PDT mechanism and the hypoxic tumor microenvironment.

3. In vivo results suggest that the tTDCR nanoparticles can lead to a complete removal of a tumor in mice without any relapse, upon a single PDT treatment in the absence of any immune checkpoint inhibitor or immunoadjuvant. This would appear to be attributed to its excellent performance in the activating macrophages. 

Dr. Guang Yang, a post-doctoral at SUSTech, is the first author of this paper. Prof. Kai Li, also of SUSTech, is the corresponding author. Jen-Shyang Ni, Yaxi Li, Menglei Zha, and Yao Tu are the co-authors of the paper.

This research was financially supported by the National Natural Science Foundation of China (NSFC), Ministry of Science and Technology of China (MOST), Guangdong Science and Technology Department, and the Shenzhen Science and Technology Program.

Paper Link: https://onlinelibrary.wiley.com/doi/10.1002/anie.202013228

Piconewton-force Dots created for Nanoscale Biomechanics Measurement

Optical tweezers are widely used in materials assembly, characterization, biomechanical force sensing, and the in vivo manipulation of cells and organs. The trapping force has primarily been generated through the refractive index mismatch between a trapped object and its surrounding medium. This poses a fundamental challenge for the optical trapping of low-refractive-index nanoscale objects, including nanoparticles and intracellular organelles.

Prof. Dayong Jin, Chair Professor at SUSTech Department of Biomedical Engineering (BME) and Distinguished Professor at the University of Technology Sydney (UTS), was part of an international collaborative research team that published an article on February 18, 2021, in Nature Nanotechnology, titled as “Optical tweezers beyond refractive index mismatch using highly doped upconversion nanoparticles.”

The research focuses on a technology that employs a resonance effect to enhance the permittivity and polarizability of nanocrystals, leading to enhanced optical trapping forces by orders of magnitude. This effectively bypasses the requirement of refractive index mismatch at the nanoscale.

Figure 1. Comparison between optical trapping of low refractive index nanoparticles with or without doping by lanthanide ions

The study shows that under resonance conditions, highly doping lanthanide ions in NaYF4 nanocrystals makes the real part of the Clausius–Mossotti factor approach its asymptotic limit, thereby achieving a maximum optical trap stiffness of 0.086 pN μm–1 mW–1 for 23.3-nm-radius low-refractive-index (1.46) nanoparticles, that is, more than 30 times stronger than the reported value for gold nanoparticles of the same size.

Figure 2. Escape velocity measurements to quantify the trap stiffness for HeLa cells with and without lanthanide-doped nanoparticles.

In conclusion, this study discovered that highly doping lanthanide ions in single nanoparticles can generate a strong oscillation resonance effect in the electromagnetic field and thereby substantially enhance the optical trapping force. This strategy can bypass the limitation set by the refractive index mismatch between an object and its surrounding medium, suggesting a new way to design far-field optical tweezers on the nanoscale. Also, benefiting from the limited heat generation, compared with gold nanoparticles, this work opens the door to a highly efficient, long-term, optical manipulation of biological samples. Furthermore, lanthanide-doped nanoparticles can be designed to be responsive to the surrounding temperature and pH values, and to enable multimodal manipulation.

Mr. Xuchen Shan from the UTS Institute for Biomedical Materials & Devices (IBMD) was the lead author of the paper. Dr. Fan Wang of UTS, Dr. Peter J. Reece of the University of New South Wales (UNSW Sydney), and Prof. Dayong Jin of SUSTech and UTS, are the corresponding authors.

The scholars acknowledge financial support from a UTS Chancellor’s Postdoctoral Research Fellowship, Australian Research Council (ARC) DECRA fellowship, the ARC Discovery Project, the National Natural Science Foundation of China (NSFC), Science and Technology Innovation Commission of Shenzhen, and the Australia–China Science and Research Fund Joint Research Centre for Point-of-Care Testing.

Paper link: https://www.nature.com/articles/s41565-021-00852-0  

BGI visiting BME SUSTech

Co-founder and President of Beijing Genome Institute (BGI), Dr. Wang Jian, along with Dr. Yu Hao , supervisor of the BGI group Board Office visited the SUSTech Department of Biomedical Engineering (BME SUSTech) on the 7th of December evening. Assoc. Professor Chen Fangyi, Assoc. Professor Likai, Asst. Professor Guo Qiongyu, Asst. Professor Ho Chun Loong, Asst. Professor Liu Chao and Miss Deng Dandan were in attendance to welcome the BGI entourage, aiming to foster closer collaborative ties through the many research projects that are ongoing in the various laboratories.

President Wang highlighted the various potential collaborative work in multi-omic analysis with key foci on proteomic, metagenomic, and transcriptomic analysis. The multi-omic research provides tools to help further propel the development and later commercialization of the technologies established in BME SUSTech. President Wang emphasized his intent to further contribute to the Pearl Delta region’s growth and research advancement through closer collaboration with SUSTech. Preliminary discussions include many key research work within the department’s main research areas, including mechanomedicine, multiscale/multimodal biomedical imaging, wearable devices and wireless monitoring, biomedical MEMS, de novo regenerative engineering, computational medicine for big data, and health informatics. This BGI-BME SUSTech visit embodies both parties’ commitment to the continual collaboration to thrust the technological development and nurturing of specialized-trained workforce within the region.

The BGI-BME SUSTech visit. (from left to right: Assoc. Professor Likai, Asst. Professor Guo Qiongyu, President Wang Jian, Asst. Professor Liu Chao, Assoc. Professor Chen Fangyi, Asst. Professor Ho Chun Loong)

President Wang Jian (second from the right) and Dr. Yu Hao (center) explaining BGI’s latest technological advancement to the members of SUSTech BME.

Asst. Professor Ho Chun Loong explaining his research work to President Wang Jian and Dr. Yu Hao during their visit to his laboratory.

 

Reported by DENG Dandan

SUSTech researchers create super-resolution “street view” of intracellular organelles’ interactions

The study of organelles’ dynamics and their interactions have been limited by optical diffraction. Recently, teams from the Chair Prof. Dayong Jin at SUSTech and Prof. Xi Peng (Peking University) successfully created a super-resolution “street view” of intracellular organelles’ interactions and has this published in Nature Communications.

This is the first time that researchers get the dynamics of lipid heterogeneity inside subcellular organelles with optical imaging technology. They have developed a Spectrum and Polarization Optical Tomography (SPOT) technique, which can resolve the membrane morphology, polarity, and phase from the intensity, spectrum, and polarization, respectively. Combined with lipophilic probes, the team successfully revealed more than ten types of organelles simultaneously and analyzed their sophisticated lipid dynamics.

A cell is a self-efficient “micro-world” with various organelles responsible for nutrition import, metabolism, endocrine modulation, protein manufacturing, waste transportations, and all the efficient communications. The study of organelles’ dynamics and their interactions will help us understand the cell functions and diagnose the cause of diseases, as well as develop potential drug treatments. As widely-used fluorescence microscopy has limits in the color and type of fluorescent dyes and in temporal and spatial resolutions, it is extremely difficult to get simultaneous imaging of multiple organelle species.

Lipid membranes in subcellular compartments synergistically regulate biophysical membrane properties, membrane protein function, and lipid-protein interactions. Despite its significant role in biochemical function and interaction of subcellular organelles, due to their similar chemical composition, it is challenging to study the classification and interaction of different types of lipid membranes and observe their dynamics for a long time.

Compared with the other existing fluorescence microscopy techniques, SPOT is superior in optical throughput that correlatively obtains the high-dimensional information from six raw images within tens of milliseconds. SPOT’s optical section ability improves the measurement accuracy of polarity and phase. This is the first time that researchers quantitatively study the lipid heterogeneity inside subcellular organelles.

Figure 1 Heterogeneity of subcellular lipid membranes revealed by SPOT.

With SPOT, the lipid heterogeneity on the outer membrane and the cristae of mitochondria, as well as lipid dynamics through endosome maturation, can be clearly imaged in real-time. With the new imaging platform established at SUSTech, researchers observed the multi-organelle interactive activities of cell division, lipid dynamics during the plasma membrane separation, tunneling nanotubules formation, and mitochondrial cristae dissociation.

Figure 2 Time-lapse high-dimensional super-resolution imaging of the late-stage division of two U2-OS cells

Figure 3 Dynamic changes of lipid membrane during mitochondrial cristae dissociation

Most microscopes can only image four or fewer color channels, far less than the types of intracellular organelles. The synergistic use of membrane morphology, lipid polarity, and the lipid phase can classify more than ten types of organelles.

SUSTech Research Assistant Professor Karl Zhanghao is the co-first author and the co-corresponding author of the work. His contribution includes: (1) Super-resolution Dipole Orientation Mapping (SDOM) technique, (Light: Sci. Appl. 2016, https://doi.org/10.1038/s41467-019-12681-w, highlighted by Nat. Methods, https://doi.org/10.1038/nmeth.4061); (2) polarized Structured Illumination Microscopy (pSIM) technique, (https://10.1038/s41467-019-12681-w, highlighted by Nat. Methods, https://doi.org/10.1038/s41592-019-0682-6); (3) pSIM with improved imaging resolution (Opt. Express, https://doi.org/10.1364/OE.395092), and low-cost SIM with laser interference and digital micro-mirror device (Appl. Phys. Lett. 2020, https://doi.org/10.1063/5.0008264).

Doctoral students Wenhui Liu from Tsinghua University, and Meiqi Li from Peking University are the co-first authors of this work.

This work has been supported by the National Natural Science Foundation of China, National Key Research and Development Program of China, Beijing Natural Science Foundation, and Shenzhen Science and Technology Program.

Article Link：https://doi.org/10.1038/s41467-020-19747-0

SUSTech professors achieve breakthrough in electronic blood vessels

Chen HANG, Ran XIAO | 10/27/2020 27
 

Researchers from Southern University of Science and Technology (SUSTech) and Fuwai Hospital of the Chinese Academy of Medical Sciences ( referred to as “Fuwai Hospital”) have developed electronic blood vessels that can be actively tuned to address subtle changes in the body after implantation. The research, published in the journal Matter, entitled “Electronic Blood Vessel.”

By using poly(L-lactide-co-ε-caprolactone) (PLC), the electronic blood vessels are made to encapsulate liquid metal to achieve the flexible and biodegradable circuit. It could also overcome the limitations of conventional tissue-engineered blood vessels (TEBVs), which serve as passive scaffolds., This could be achieved by coordinating with other electronic devices to deliver genetic material, enable controlled drug release, and facilitate the formation of new endothelial blood vessel tissue.

The electronic blood vessels could integrate flexible electrons with three layers of blood vessel cells to imitate and surpass natural blood vessels. It can effectively promote cell proliferation and migration in the wound healing model through electrical stimulation. It can controllably deliver genes to specific parts of the blood vessel through electro-transfection. Through a 3-month in vivo study of the rabbit carotid artery replacement model, the authors evaluated the electronic blood vessel’s efficacy and biological safety in the vascular system. They confirmed its patency through ultrasound imaging and angiography. The research paves the way for the integration of flexible, degradable bioelectronics into the vascular system, which can be used as a platform for further treatments, such as gene therapy, electrical stimulation, and electronically controlled drug release.

Electronic blood vessels show the potential to play a key role in the treatment of cardiovascular disease. In the treatment of cardiovascular disease through coronary artery bypass grafting, the existing small diameter (<6 mm) tissue-engineered blood vessels (TEBV) have not yet met clinical needs. The methods used in most studies only provide TEBV with a stent that provides mechanical support, which mainly relies on the remodeling process of host tissues but has obvious limitations in helping to regenerate new blood vessels. Specifically, the complex interaction between blood flow and TEBV usually causes resonance reactions, leading to problems such as thrombus formation and neointimal hyperplasia. Instead, the new generation of TEBV should have enough apical stents to provide mechanical support and the ability to respond and integrate with the remodeling process actively to provide adaptive treatment after implantation.

In Situ Monitoring of the Electronic Blood Vessel

(A) Schematic of the electronic blood vessel in the carotid artery of the rabbit.
(B and C) An end-to-end anastomosis procedure of electronic blood vessel implantation in carotid arteries of rabbits (n = 6). The dotted frames (B and C)outline the margin of the native carotid artery and the implanted electronic blood vessel. The white arrows (C) indicate the two ends of the electronic blood vessel. Scale bar, 1 cm.
(D–G) In situmonitoring of the electronic blood vessel by Doppler ultrasound imaging 3 months post-implantation. Representative images from at least three different animals. (D and E) The real-time blood flow at the operational site and the synchronized ultrasound pulses. The asymmetric velocity curve indicates that the signal is from the carotid artery rather than the vein. (E) Zoom-in view of red box in (D). (F) The cross-sectional view of the blood flow.
(G) The suture site (red arrows) connecting the native carotid artery and the electronic blood vessel.
(H) The diameter changes in the electronic blood vessel at different times post-implantation.
(I) The velocity of blood flow at the operational site (n = 18, from different rabbits at different time points).
(J and K) In situ monitoring by arteriography 3months post-implantation. (J) Image before injecting the contrastmedium. Red box indicates the position of the implanted electronic blood vessel. Scale bar, 1 cm.
(K) Image after injecting the contrast medium. Red box indicates the position of the implanted blood vessel. Red arrows indicate the suture sites connecting the native carotid artery and the electronic blood vessel. Scale bar, 1 cm.

The team uses a PTFE mandrel, forming a 3D multi-layered tubular structure with PLC-based metal-polymer conductor (MPC) membranes. The inner diameter of the electronic blood vessel is about 2 mm, which is flexible and degradable. The MPC circuit has excellent conductivity and can be well distributed in the three-dimensional multilayer tubular structure. Studies have found that electronic blood vessels also have excellent cell safety, including the three cultured vascular cells (human umbilical vein endothelial cells, human aortic smooth muscle cells, and human aortic fibroblasts).

The team also constructed a 3D electrical function model to stimulate endothelial cells in vitro through electrochemical workstations to promote their proliferation and migration. Simultaneously, three kinds of blood vessel cells were patterned on the 3D electronic blood vessel, and the GFP plasmid was electroporated in vitro by an electroporation instrument. After two days of culture, the expression of the plasmid was observed.

The team chose rabbits from New Zealand as the animal model, replacing the common carotid artery with electronic blood vessels. The implanted electronic blood vessels were monitored by Doppler ultrasound imaging and arteriography. According to Doppler ultrasound imaging, three months after implantation, the electronic blood vessel allows stable blood flow to pass, showing the electronic blood vessel’s excellent patency. In the future, the electronic blood vessel can be integrated with other electronic components and devices to achieve diagnostic and therapeutic functions. This will enhance significantly personalized medical functions by establishing a direct connection in the blood vessel tissue-machine interface.

Shiyu Cheng, Chen Hang, and Li Ding are the joint first authors of the paper, and Yan Zhang (Fuwai Hospital) and Xingyu Jiang (SUSTech)are the corresponding authors.

Link to the paper: https://www.sciencedirect.com/science/article/pii/S2590238520304938