Chaozong Liu
University College London, Institute of Biomedical Engineering, Faculty Member
Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Statistical Analysis, Experimental Design, and 15 moreSurface Chemistry, Plasma Processing, Polymer, Surface modification, Poly (lactic acid), Plasma, Contact angle, Wetting, Surface treatment, Surface Properties, Polyimide, Dielectric Barrier Discharge, X Ray Photoelectron Spectroscopy, Electrode, and Polytetrafluoroethylene
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Research Interests: Condensed Matter Physics, Materials Science, Quantum Physics, Surface Science, Data Analysis, and 15 moreStatistical Analysis, Experimental Design, Surface Chemistry, Plasma Processing, Polymer, Surface modification, DIELECTRIC, Atmospheric Pressure, Contact angle, Orthogonal Array, Surface Properties, Microstructures, Dielectric Barrier Discharge, Electrode, and Process Parameters
We extracted magnesium-rich calcium phosphate bioceramics from tilapia bone using a gradient thermal treatment approach and investigated their chemical and physicochemical properties. X-ray diffraction showed that tilapia fish... more
We extracted magnesium-rich calcium phosphate bioceramics from tilapia bone using a gradient thermal treatment approach and investigated their chemical and physicochemical properties. X-ray diffraction showed that tilapia fish bone-derived hydroxyapatite (FHA) was generated through the first stage of thermal processing at 600–800 °C. Using FHA as a precursor, fish bone biphasic calcium phosphate (FBCP) was produced after the second stage of thermal processing at 900–1200 °C. The beta-tricalcium phosphate content in the FBCP increased with an increasing calcination temperature. The fact that the lattice spacing of the FHA and FBCP was smaller than that of commercial hydroxyapatite (CHA) suggests that Mg-substituted calcium phosphate was produced via the gradient thermal treatment. Both the FHA and FBCP contained considerable quantities of magnesium, with the FHA having a higher concentration. In addition, the FHA and FBCP, particularly the FBCP, degraded faster than the CHA. After on...
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A novel biomimetic osteochondral scaffold based on PLGA framework reinforced collagen/hydroxyapatite composite system has been prepared by using 3D fabrication integrated technology. The resultant osteochondral scaffolds have been... more
A novel biomimetic osteochondral scaffold based on PLGA framework reinforced collagen/hydroxyapatite composite system has been prepared by using 3D fabrication integrated technology. The resultant osteochondral scaffolds have been examined with respect to microstructure and mechanical properties. It was observed that the osteochondral scaffold demonstrated gradient structure and progressive mechanical strength that recapitulate the physical environment of the osteochondral tissue unit. In vivo rabbit model evaluation indicated the osteochondral scaffold has the ability to achieve stable mechanical fixation, leading to improved cartilage fill and enhance hyaline cartilage and bone formation. However, there are still challenges in developing “ideal” osteochondral scaffold to achieve clinically satisfactory outcomes.
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Intraosseous Transcutaneous Amputation Prosthesis (ITAP) is a new generation of limb replacements that can provide to amputees, an alternative solution to the main problems caused by the most commo...
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Osseointegrated transcutaneous implants could provide an alternative and improved means of attaching artificial limbs for amputees, however epithelial down growth, inflammation, and infections are common failure modalities associated with... more
Osseointegrated transcutaneous implants could provide an alternative and improved means of attaching artificial limbs for amputees, however epithelial down growth, inflammation, and infections are common failure modalities associated with their use. To overcome these problems, a tight seal associated with the epidermal and dermal adhesion to the implant is crucial. This could be achieved with specific biomaterials (that mimic the surrounding tissue), or a tissue-specific design to enhance the proliferation and attachment of dermal fibroblasts and keratinocytes. The intraosseous transcutaneous amputation prosthesis is a new device with a pylon and a flange, which is specifically designed for optimising soft tissue attachment. Previously the flange has been fabricated using traditional machining techniques, however, the advent of additive layer manufacturing (ALM) has enabled 3-dimensional porous flanges with specific pore sizes to be used to optimise soft tissue integration and reduce failure of osseointegrated transcutaneous implants. The study aimed to investigate the effect of ALM-manufactured porous flanges on soft tissue ingrowth and attachment in an in vivo ovine model that replicates an osseointegrated percutaneous implant. At 12 and 24 weeks, epithelial downgrowth, dermal attachment and revascularisation into ALM-manufactured flanges with three different pore sizes were compared with machined controls where the pores were made using conventional drilling. The pore sizes of the ALM flanges were 700, 1000 and 1250 μm. We hypothesised that ALM porous flanges would reduce downgrowth, improve soft tissue integration and revascularisation compared with machined controls. The results supported our hypothesis with significantly greater soft tissue integration and revascularisation in ALM porous flanges compared with machined controls.
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Scaffolds are an important aspect of the tissue engineering approach to tissue regeneration. This study shows that it is possible to manufacture scaffolds from type I collagen with or without hydroxyapatite (HA) by critical point drying.... more
Scaffolds are an important aspect of the tissue engineering approach to tissue regeneration. This study shows that it is possible to manufacture scaffolds from type I collagen with or without hydroxyapatite (HA) by critical point drying. The mean pore sizes of the scaffolds can be altered from 44 to 135 microm depending on the precise processing conditions. Such pore sizes span the range that is likely to be required for specific cells. The mechanical properties of the scaffolds have been measured and behave as expected of foam structures. The degradation rate of the scaffolds by collagenase is independent of pore size. Dehydrothermal treatment (DHT), a common method of physically crosslinking collagen, was found to denature the collagen at a temperature of 120 degrees C resulting in a decrease in the scaffold's resistance to collagenase. Hybrid scaffold structures have also been manufactured, which have the potential to be used in the generation of multi-tissue interfaces. Microchannels are neatly incorporated via an indirect solid freeform fabrication (SFF) process, which could aid in reducing the different constraints commonly observed with other scaffolds.
Research Interests: Materials Engineering, Materials Science, Biomedical Engineering, Hydroxyapatite, Crystallization, and 15 moreExtracellular Matrix, Elasticity, Bone Tissue Engineering, Absorption, Desiccation, Biomimetic materials, Bone Substitutes, Materials Testing, Durapatite, Biocompatible Materials, Critical Point, Collagenase, Mechanical Property, Collagen type I, and Cell culture techniques
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INTRODUCTION: The mechanical properties and structure of such gels play an important role in the regulation of cell growth, ECM secretion and consequent tissue formation. In this study, the viscoelastic performance, micro-structure and... more
INTRODUCTION: The mechanical properties and structure of such gels play an important role in the regulation of cell growth, ECM secretion and consequent tissue formation. In this study, the viscoelastic performance, micro-structure and permeability of the resulting gels were determined with the aim of developing an appropriate scaffold for IVD NP tissue engineering that could be consistently processed. METHODS: The CHEMICON ® 3D collagen cell culture system (collagen type I from rat tail, CHEMICON ® International, UK) was used as model scaffold. The gelation process was monitored using a TA ARES Rheometer. A house made permeability tester was used to measure the permeability of the gel scaffolds. The tests were performed at 37 o C under different hydrostatic pressure using DMEM medium as test liquid. The flow volume (V, ml) of the medium perfusion through gels was calculated from the weight measured via an electronic scale, and the permeability (K, m 4 /Ns) was calculated using the following modified version of Darcy law: 11 2 10
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Polyether-ether-ketone (PEEK) is believed to be the next-generation biomedical material for orthopaedic implants that may replace metal materials because of its good biocompatibility, appropriate mechanical properties and radiolucency.... more
Polyether-ether-ketone (PEEK) is believed to be the next-generation biomedical material for orthopaedic implants that may replace metal materials because of its good biocompatibility, appropriate mechanical properties and radiolucency. Currently, some PEEK implants have been used successfully for many years. However, there is no customised PEEK orthopaedic implant made by additive manufacturing licensed for the market, although clinical trials have been increasingly reported. In this review article, design criteria, including geometric matching, functional restoration, strength safety, early fixation, long-term stability and manufacturing capability, are summarised, focusing on the clinical requirements. An integrated framework of design and manufacturing processes to create customised PEEK implants is presented, and several typical clinical applications such as cranioplasty patches, rib prostheses, mandibular prostheses, scapula prostheses and femoral prostheses are described. The main technical challenge faced by PEEK orthopaedic implants lies in the poor bonding with bone and soft tissue due to its biological inertness, which may be solved by adding bioactive fillers and manufacturing porous architecture. The lack of technical standards is also one of the major factors preventing additive-manufactured customised PEEK orthopaedic implants from clinical translation, and it is good to see that the abundance of standards in the field of additive-manufactured medical devices is helping them enter the clinical market.
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During the present study, a double groove texture was designed on the surface of a piston ring to improve the sealing performance between the piston ring and cylinder liner. The experimental design method was used to fabricate the test... more
During the present study, a double groove texture was designed on the surface of a piston ring to improve the sealing performance between the piston ring and cylinder liner. The experimental design method was used to fabricate the test plan according to the groove width, depth, and spacing. By using the thermal–structural coupling analysis method, the finite element analysis of the standard piston ring and the textured piston ring was carried out to simulate the deformation state of the cylinder liner system of the piston ring group during the working stroke. The piston rings with different parameters designed by the test scheme were manufactured by wire electrical discharge machining, and the self-made experiment device carried out the sealing test. The results showed that the groove texture could improve the sealing performance of the piston ring, and the analyzed results demonstrated that the groove texture had little effect on the maximum deformation of the piston ring. Still, i...
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Research Interests: Medicine and Chest Pain
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Human tissues and organs are inherently heterogeneous, and their functionality is determined by the interplay between different cell types, their secondary architecture, and gradients of signalling molecules and metabolites. To mimic the... more
Human tissues and organs are inherently heterogeneous, and their functionality is determined by the interplay between different cell types, their secondary architecture, and gradients of signalling molecules and metabolites. To mimic the dynamics of native tissues, perfusion bioreactors and microfluidic devices are widely used in tissue engineering (TE) applications for enhancing cell culture viability in the core of 3D constructs. Still, most in vitro screening methods for compound efficacy and toxicity assessment include cell or tissue exposure to constant and homogeneous compound concentrations over a defined testing period. Moreover, a prevalent issue inhibiting the large-scale adoption of microfluidics and bioreactor is the tubing dependence to induce a perfusion regime. Here, we propose a compartmentalized rotational (CR) 3D cell culture platform for a stable control over gradient tissue culture conditions. Using the CR bioreactor, adjacent lanes of constructs are patterned by...
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Oral health is crucial to daily life, yet many people worldwide suffer from oral diseases. With the development of oral tissue engineering, there is a growing demand for dental biomaterials. Addressing oral diseases often requires a... more
Oral health is crucial to daily life, yet many people worldwide suffer from oral diseases. With the development of oral tissue engineering, there is a growing demand for dental biomaterials. Addressing oral diseases often requires a two-fold approach: fighting bacterial infections and promoting tissue growth. Hydrogels are promising tissue engineering biomaterials that show great potential for oral tissue regeneration and drug delivery. In this review, we present a classification of hydrogels commonly used in dental research, including natural and synthetic hydrogels. Furthermore, recent applications of these hydrogels in endodontic restorations, periodontal tissues, mandibular and oral soft tissue restorations, and related clinical studies are also discussed, including various antimicrobial and tissue growth promotion strategies used in the dental applications of hydrogels. While hydrogels have been increasingly studied in oral tissue engineering, there are still some challenges th...
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ObjectiveAn analysis of the relationship between rheumatoid arthritis (RA) and copper death-related genes (CRG) was explored based on the GEO dataset.MethodsBased on the differential gene expression profiles in the GSE93272 dataset, their... more
ObjectiveAn analysis of the relationship between rheumatoid arthritis (RA) and copper death-related genes (CRG) was explored based on the GEO dataset.MethodsBased on the differential gene expression profiles in the GSE93272 dataset, their relationship to CRG and immune signature were analysed. Using 232 RA samples, molecular clusters with CRG were delineated and analysed for expression and immune infiltration. Genes specific to the CRGcluster were identified by the WGCNA algorithm. Four machine learning models were then built and validated after selecting the optimal model to obtain the significant predicted genes, and validated by constructing RA rat models.ResultsThe location of the 13 CRGs on the chromosome was determined and, except for GCSH. LIPT1, FDX1, DLD, DBT, LIAS and ATP7A were expressed at significantly higher levels in RA samples than in non-RA, and DLST was significantly lower. RA samples were significantly expressed in immune cells such as B cells memory and different...
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Stress shielding secondary to bone resorption is one of the main causes of aseptic loosening, which limits the lifespan of hip prostheses and exacerbates revision surgery rates. In order to minimise post-hip replacement stress variations,... more
Stress shielding secondary to bone resorption is one of the main causes of aseptic loosening, which limits the lifespan of hip prostheses and exacerbates revision surgery rates. In order to minimise post-hip replacement stress variations, this investigation proposes a low-stiffness, porous Ti6Al4V hip prosthesis, developed through selective laser melting (SLM). The stress shielding effect and potential bone resorption properties of the porous hip implant were investigated through both in vitro quasi-physiological experimental assays, together with finite element analysis. A solid hip implant was incorporated in this investigation for contrast, as a control group. The stiffness and fatigue properties of both the solid and the porous hip implants were measured through compression tests. The safety factor of the porous hip stem under both static and dynamic loading patterns was obtained through simulation. The porous hip implant was inserted into Sawbone/PMMA cement and was loaded to 2...
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Research Interests: Chemistry and Homogeneous
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3D-printed polylactic acid (PLA) scaffolds have been demonstrated as being a promising tool for the development of tissue-engineered replacements of bone. However, this material lacks a suitable surface chemistry to efficiently interact... more
3D-printed polylactic acid (PLA) scaffolds have been demonstrated as being a promising tool for the development of tissue-engineered replacements of bone. However, this material lacks a suitable surface chemistry to efficiently interact with extracellular proteins and, consequently, to integrate into the surrounding tissue when implanted in vivo. In this study, aloe vera coatings have been proposed as a strategy to improve the bioaffinity of this type of structures. Aloe vera coatings were applied at three different values of pH (3, 4 and 5), after treating the surface of the PLA scaffolds with oxygen plasma. The surface modification of the material has been assessed through X-ray photoelectron spectroscopy (XPS) analysis and water contact angle measurements. In addition, the evaluation of the enzymatic degradation of the structures showed that the pH of the aloe vera extracts used as coating influences the degradation rate of the PLA-based scaffolds. Finally, the cell metabolic act...