Multifunctional Gel Scaffolds for Cell Delivery and Tissue Repair

Lead Research Organisation: University of Bolton
Department Name: Centre for Materials Res and Innovation

Abstract

Injectable biomaterial scaffolds for tissue reconstruction are still not a clinical reality because many of the scaffold design parameters have not been fully optimized and controlled. New multifunctional scaffolds that both mimic the mechanical properties and structure of natural tissues and are able to promote cell adhesion, proliferation and differentiation are now urgently needed. The aim of this project is to develop new hyper-branched poly(glycidol)/poly(caprolactam) (HBPG/PCL) based injectable gel scaffolds that have the potential to enable bone growth and the regeneration of cartilage in vivo, following application in a minimally invasive manner. They will thereby enable effective treatment of osteoarthritis (OA) without surgery. OA is characterized pathologically by localised loss of cartilage, remodeling of adjacent bone and associated inflammation. OA is one of the leading causes of pain and disability worldwide. New covalently-linked scaffolds that exhibit gradually increasing mechanical strength will be formed in vivo from physically cross-linked HBPG/PCL particles in a safe and effective way, in the absence of UV-radiation. They will feature tunable elastic modulus values and will undergo enzyme-triggered disassembly. The proposal will benefit the NHS by improving patients' quality of life, reducing surgical costs and boost the UK economy by shortening patient recovery times and reducing productivity losses due to disability and/or illness. The proposal greatly extends Dr. Halacheva's earlier studies on biomaterials scaffolds and will be conducted by a postdoctoral research associate (PDRA) and a University of Bolton funded Ph.D. student over a period of 15 months.

Planned Impact

Who will benefit and how?
Osteoarthritis (OA) is a degenerative joint disease which currently affects 10 - 15% of people over the age of 60, worldwide. The cost and burden of OA is anticipated to expand greatly due to the increasing average age and bodyweight of the world's population. Herein we aim to establish a new injectable gel technology that has long term potential to regenerate cartilage and bone tissue in vivo. The project will tackle the current gap in knowledge and provide an important step in the optimisation of injectable gel scaffolds intended to be used as a minimally invasive treatment for tissue disorders. The main beneficiaries of the project will be:

Patients: OA is the most common cause of disability in the UK. Pain, stiffness, joint deformity and loss of joint mobility have a substantial impact on individuals' quality of life. From a clinical perspective, the HBPG/PCL injectable scaffolds that are proposed to be developed will have the potential to minimise patient discomfort, risk of infection, scar formation, and the overall cost of treatment. Current treatment strategies for OA involve joint repair or total replacement using implants. The surgery does not restore the native tissue or reinstate natural biomechanical properties. The new HBPG/PCL injectable gels will enable regeneration of native bone or cartilage tissue in vivo without invasive surgery. Our approach has potential to provide a quick patient recovery time and long term pain relief from OA.

UK economy: OA has a significant negative impact on the UK economy, with its total cost estimated to be 1% of GNP per year. In 2010-2011, £43 million was spent on community services and £215 million was spent on social services due to OA (see Pathways for Impact). In this proposal new injectable scaffolds will be developed that have the potential to reduce the treatment costs associated with OA and impart a positive impact upon the UK economy.

Healthcare organization: OA exerts a considerly negative impact on health services. Approximately two million adults per year visit their GP due to OA. Over a one-year period (2013-2014) there were 114,500 hospital admissions in the UK alone. The project will improve the quality of life by developing a minimally invasive treatment solution for OA that will not require hospitalisation or long recovery times.

Professional bodies: EPSRC, TSB, BBSRC, MRC, Biomedical Research centres and units and the NHS will benefit from the novel approach for preparation of the injectable biomaterials that demonstrate improved biomechanical properties and controlled cell differentiation and propagation.

Academics: See the section entitled Academic Beneficiaries.

People: The research programme will train a PDRA by providing him/her with the opportunity to work in partnership with a Ph.D. student, Dr.Halacheva and staff from the collaborating organisations. The PDRA will attend an international conference, a UK-based workshop and will be actively involved in engagement activities with national and international research teams. The training of the PDRA will have a direct economic impact via provision of skilled workers who may subsequently be employed by any beneficiary organisation. The project will also facilitate the development of the Biomaterials Research Centre at the IMRI, University of Bolton for the training of chemists and bioengineers.

Society: The new injectable HBPG/PCL gels will enhance the quality of life and improve the population's health by enabling effective treatment of medical conditions for which there are no existing minimally invasive therapies.

End users: NHS, Arthritis Research UK and the Multiple Sclerosis Society, industrial companies such as GE Healthcare, Smith & Nephew, and Johnson & Johnson will benefit from the novel optimised injectable scaffolds that will fulfil all the engineering design criteria for a regenerative device.

Publications

10 25 50
 
Description A series of new trimethoxysilane capped thermoresponsive PCL-HBPG- copolymers (PCL-HBPG/SiHBPG) are synthesised by anionic polymerization of glycidol and 3-glycidyloxypropyltrimethoxysilane in the absence of cytotoxic reagents. For our systems, the increased content of HBPG and SiHBPG resulted in a reduction in polymer mobility and hence an increase in Tg owing to the increase in inter- and intra-chain H-bonds interactions between HBPG and SiHBPG moieties. The PCL-HBPG/1SiHBPG copolymers showed improved thermal stabilities.
They are amphiphilic and readily self-assemble in aqueous solutions into micelles composed of a hydrophobic PCL inner core and a surrounding shell of hydrophilic HBPG. The CMC values were determined at four temperatures. The CMCs of the polymers were only slightly affected by temperature. However, this trend is somehow unexpected as the PCL is hydrophobic in the entire temperature range, whereas as shown previously the solubility of the polyglycidol increases at elevated temperatures. Therefore, we would expect an increase of CMCs with increasing temperature. At lower temperatures, the PCL chains in PCL-HBPG/SiHBPG copolymers loop and the HBPG/SiHBPG branches cover them to decrease their unfavourable interactions with water. At elevated temperatures the solubility of polyglycidol increases. This weaken the steric protection of the HBPG/SiHBPG branches and results to exposing the whole hydrophobic PCL to water. This facilitates micelle aggregation and decreases the CMC. To further explore the anomalous temperature behaviour of the aqueous solutions of the PCL-HBPG/1SiHBPG copolymers we investigated the variations of the transmittance of light with the temperature at concentrations above the CMC. Three types of transmitance v/s temperature curve patterns have been reported.
The internal structure of the HBPG-PCl/SiHBPG particles, their size, MW and aggregation number were studied by (static light scattering), SLS and SAXS. The PCL-HBPG/SiHBPG polymers formed relatively large spherical particles (ten of nm and millions in molar mass), which are spherical in shape. The particles were segregated into hydrophobic (PCL) and hydrophilic domains (HBPG) domains. The shape of the domains depended strongly upon the copolymer composition, temperature, and concentration. These structures were interconnected presumably via Si moieties.
In the next stage of the project, we utilised a completely new approach for the development PCL-HBPG/SiHBPG-based gels . Our simple method is based on dual gelation of a crosslinked aqueous dispersion of thermo-responsive copolymer particles which does not involve the use of harmful UV-mediated photocrosslinking, free radicals or toxic metal catalysts. The gels are derived in two steps: firstly, the physical gels are formed from a concentrated dispersion of PCL-HBPG/SiHBPG particles upon exposure to physiological temperature conditions. In the second step, the physical network is locked in place in vivo due to the gradual hydrolysis (and subsequent Si-O-Si crosslink formation) of trimethoxysilane groups. The gels feature tuneable elastic modulus values and undergo enzyme-triggered disassembly. The cytotoxicity of the new hollow particle gels was tested for the first time using chondrocyte cells and related to gels' composition, mechanical properties, and morphology. The covalently-linked gels exhibit gradually increasing mechanical strength over time (as the extent of methoxysilane hydrolysis and crosslinking proceeds), as well as tuneable degradation kinetics and therefore are particularly attractive in space filling and load bearing applications.
Exploitation Route The new HBPG/PCL scaffolds could provide a new minimally invasive treatment for OA that is currently non-existent. The new treatment has the potential to enhance the quality of life and health by addressing medical conditions for which there are no existing minimally invasive therapies.The new findings will contribute to significant advances in understanding, methodology, theory and application of injectable scaffolds for treatment of tissue disorders. The new physiologically compatible approach for the preparation of the gel scaffolds could be utilised by other researchers.
Sectors Chemicals,Healthcare,Pharmaceuticals and Medical Biotechnology

URL https://www.researchgate.net/project/Multifunctional-Gel-Scaffolds-for-Cell-Delivery-and-Tissue-Repair
 
Description Osteoarthritis (OA) represents an increasing economic burden to the UK, both from direct and indirect costs. In 2010-2011 approximately 181,350 patients suffering with OA were admitted to hospital in the UK. The resulting cost of hip and knee replacements was estimated to exceed £850 million whereas the indirect costs from OA caused over £3.2 billion in loss of economic production, £43 million was spent on community care and £215 million on social services. There is a clear societal support and economic impact of the project in terms of importance to UK healthcare and global economics. It offers a new minimally invasive therapy which will reduce the treatment costs associated with OA, will enhance the quality of life and reduce the pain, recovery times and morbidity in patients. The project have the potential to foster global economic performance, to improve the UK's economic competitiveness, to increase effectiveness of public services and policy and to enhance health and creative output. The project's findings contribute to expanding of the existing knowledge concerning synthetic polymer-based biomaterials in general, particularly those which are to be used as injectable gels for tissue repair purposes. The both synthetic route employed for the preparation of the PCL-HBPG/SIHBPG copolymers and the strategy utilised for the development of injectable PCL-HBPG/SIHBPG-based gel scaffolds constitute novel applications and improvements of pre-existing methodologies which may be of use to the wider polymer chemistry community.
Sector Chemicals,Education
Impact Types Societal,Economic

 
Description PhD student bursary
Amount £41,178 (GBP)
Organisation University of Bolton 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 09/2017
 
Title Development of novel PCL-HBPG/SiHBPG-based gel scaffolds by a simple chemical procedure which does not require the use of toxic or costly reagents. 
Description A simple chemical procedure which does not require the use of toxic or costly reagents was utilized for the synthesis of PCL-HBPG/SiHBPG particle gels scaffolds. Covalently-linked scaffolds that exhibit gradually increasing mechanical strength was formed from the physically crosslinked PCL-HBPG/SiHBPG particle in a safe and effective manner, in the absence of UV-radiation. Our simple method for the preparation of new load-bearing PCL-HBPG/SiHBPG gels offers the possibility to control the gels' mechanical properties, porosities, biodegradabilities and routes of cell differentiation by tuning copolymer compositions, structure and temperature. 
Type Of Material Biological samples 
Year Produced 2017 
Provided To Others? No  
Impact The prepared gel scaffolds have the potential to provide an injectable, load-supporting, biodegradable multifunctional system for tissue reconstruction from the time of injection. The scaffolds will be tissue adhesive and be able to facilitate ECM growth. These new injectable HBPG/PCL scaffolds have the potential to considerably reduce the cost to the NHS for treatment of osteoarthritis.The in vivo gel-forming system will minimise patient discomfort, risk of infection and the overall cost of treatment. The new prepared scaffolds could help the NHS to cope with the increase in demand for tissue regeneration and the rising costs of surgery. 
 
Title New injectable gel scaffolds based on polycaprolactone and trimethoxysilane capped hyperbranched polyglycidol, PCL-HBPG/SiHBPG 
Description Herein, a series of new PCL-HBPG/SiHBPG copolymers were synthesised by anionic polymerization of glycidol and 3-glycidyloxypropyltrimethoxysilane in the absence of cytotoxic reagents. Silanes are commonly used as coupling agents owing to the presence of trimethoxysilane groups that are capable of gradual hydrolysis and subsequent Si-O-Si crosslink formation. The PCL-HBPG/SiHBPG copolymers self-associated in water to form particles of various size, internal structure and morphology. The concentrated dispersions of the PCL-HBPG/SiHBPG particles were further utilized for development of injectable PCL-HBPG/SiHBPG physical gels that are able to be covalently crosslinked in vivo and give a tissue scaffold capable of supporting load and facilitating regeneration of native tissue. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact The new injectable PCL-HBPG/SiHBPG gel scaffolds have the potential to provide a new minimally invasive treatment for osteoarthritis (OA) that is currently non-existent. The therapy will reduce the treatment costs associated with OA, will enhance the quality of life and reduce the pain, recovery times and morbidity in patients. The gel scaffolds will have the potential to foster global economic performance, to improve the UK's economic competitiveness, to increase effectiveness of public services and policy and to enhance health and creative output. 
 
Description Biocompatabilities studies with the gels scaffolds 
Organisation University of Manchester
Department Manchester Medical School
Country United Kingdom 
Sector Academic/University 
PI Contribution We prepared mechanically strong gels from PCL-HBPG/SiHBPG block copolymers under physiological conditions. The gels was derived in two steps: firstly, the physical gels was formed from a concentrated dispersion of PCL-HBPG/SiHBPG particles upon exposure to physiological temperature conditions. The sol-gel transition temperature was tuned by varying the PCL block length and copolymer concentration. In the second step, the physical network was locked in place due to the gradual hydrolysis (and subsequent Si-O-Si crosslink formation) of trimethoxysilane groups. They gels feature tuneable elastic modulus values and undergo enzyme-triggered disassembly, the rate of which depends strongly upon the scaffold composition and structure.
Collaborator Contribution The Medical School, University of Manchester provided laboratory space and facilities for testing the biocompatibility and cell adhesiveness of the PCL-HBPG/SiHBPG gels with the best mechanical properties and porosity. Chondrocyte cell were used for the analysis. The cell viability was assessed by Live/Dead and MTT assays. There were no reduction in the cells viability after 48h of exposure of the cellsto the gels. Viability decresed up to 75% after 7 days of incubation.
Impact The results of this research were prepared for publication. One article titled: New Thrimetoxisilinated End-caped Hyper Branched Poly(glycidol)/Poly(caprolactam) (HBPG/PCL) Copolymers for Cell Delivery and Tissue Repair, C. Conzalez Chommon, Clara, V.Garamus, J. Ebdon, S. Rangelov, , Ch. Novakov, J. Hoyland and S. Halacheva is due to be submitted very soon to Macromolecules, an ACS journal: A second article is in preparation. Based on the new knowledge and experience generated from the project the Medical School, University of Manchester will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research. The collaboration is interdisciplinary and involves partnerships between polymer chemists and materials scientists . The collaboration will contribute to significant advances in understanding, methodology, theory and application of injectable scaffolds for treatment of tissue disorders. The project results will benefit academic researchers involved in development of novel biomaterial scaffolds for tissue repair. The successful outcomes of this project will enhance the academic profile of the University of Bolton and University of Manchester in this area. The high quality results derived from experimental tests can be used to optimise other available synthetic scaffolds for tissue repair. The collaboration is multi-disciplinary and involves collaboration between chemists, biomaterials scientists, biologists and medics.
Start Year 2017
 
Description Characterization of the Gel Scaffolds 
Organisation Bulgarian Academy of Sciences
Department Institute of Polymers
PI Contribution We were able to prepare mechanically strong gels from PCL-HBPG/SiHBPG block copolymers under physiological conditions. The gels was derived in two steps: firstly, the physical gels was formed from a concentrated dispersion of PCL-HBPG/SiHBPG particles upon exposure to physiological temperature conditions. The sol-gel transition temperature was tuned by varying the HBPG content and copolymer concentration. In the second step, the physical network was locked in place due to the gradual hydrolysis (and subsequent Si-O-Si crosslink formation) of trimethoxysilane groups.They gels feature tuneable elastic modulus values and undergo enzyme-triggered disassembly, the rate of which depends strongly upon the scaffold composition and structure. The gels's mechanical properties were characterised at the University of Bolton, using a rheometer.
Collaborator Contribution The gel structures were visualised by TEM at the IP, BAS. The morphology of the gel was also confirmed my SAXS (HZG, Germany). The internal structure of the gels and their mechanical properties were related to the particle composition, size and morphology.
Impact The results of this research were prepared for publication. One article is due to be submitted very soon to Macromolecules, an ACS journal: New Thrimetoxisilinated End-caped Hyper Branched Poly(glycidol)/Poly(caprolactam) (HBPG/PCL) Copolymers for Cell Delivery and Tissue Repair, C. Conzalez Chommon, Clara, V.Garamus, J. Ebdon, S. Rangelov, , Ch. Novakov, J. Hoyland and S. Halacheva. A second article is in preparation. The collaboration is multy-disciplinary and involves partnerships between polymer chemists, biomaterials scientists, physical chemists and physicists. The collaboration strengthens the international links between the UK, Bulgaria and Germany and will contribute to significant advances in understanding, methodology, theory and application of injectable scaffolds for treatment of tissue disorders. Based on the new knowledge and experience generated from the project the Institute of Polymers, Bulgarian Academy of Sciences and HZG, Germany will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research.
Start Year 2017
 
Description Characterization of the Gel Scaffolds 
Organisation Helmholtz Association of German Research Centres
Department Helmholtz-Zentrum Geesthacht
Country Germany 
Sector Academic/University 
PI Contribution We were able to prepare mechanically strong gels from PCL-HBPG/SiHBPG block copolymers under physiological conditions. The gels was derived in two steps: firstly, the physical gels was formed from a concentrated dispersion of PCL-HBPG/SiHBPG particles upon exposure to physiological temperature conditions. The sol-gel transition temperature was tuned by varying the HBPG content and copolymer concentration. In the second step, the physical network was locked in place due to the gradual hydrolysis (and subsequent Si-O-Si crosslink formation) of trimethoxysilane groups.They gels feature tuneable elastic modulus values and undergo enzyme-triggered disassembly, the rate of which depends strongly upon the scaffold composition and structure. The gels's mechanical properties were characterised at the University of Bolton, using a rheometer.
Collaborator Contribution The gel structures were visualised by TEM at the IP, BAS. The morphology of the gel was also confirmed my SAXS (HZG, Germany). The internal structure of the gels and their mechanical properties were related to the particle composition, size and morphology.
Impact The results of this research were prepared for publication. One article is due to be submitted very soon to Macromolecules, an ACS journal: New Thrimetoxisilinated End-caped Hyper Branched Poly(glycidol)/Poly(caprolactam) (HBPG/PCL) Copolymers for Cell Delivery and Tissue Repair, C. Conzalez Chommon, Clara, V.Garamus, J. Ebdon, S. Rangelov, , Ch. Novakov, J. Hoyland and S. Halacheva. A second article is in preparation. The collaboration is multy-disciplinary and involves partnerships between polymer chemists, biomaterials scientists, physical chemists and physicists. The collaboration strengthens the international links between the UK, Bulgaria and Germany and will contribute to significant advances in understanding, methodology, theory and application of injectable scaffolds for treatment of tissue disorders. Based on the new knowledge and experience generated from the project the Institute of Polymers, Bulgarian Academy of Sciences and HZG, Germany will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research.
Start Year 2017
 
Description Characterization of the PCL-HBPG/1SiHBPG copolymers 
Organisation Bulgarian Academy of Sciences
Country Bulgaria 
Sector Learned Society 
PI Contribution We have synthesized a series of thermo-responsive trimethoxysilane end-capped hyperbranched poly(glycidol)/poly(caprolactone) PCL-HBPG/SiHBPG copolymers of various compositions. The PCL-HBPG/SiHBPG copolymers were synthesised by anionic polymerization of a mixture of glycidol and 3-glycidyloxypropyl trimethoxysilane using partially deprotonated PCL diol with molecular weight of 2000 g/mol as a macroinitiator. A number- of polymerizations were carried out to prepare PCL-HBPG/SiHBPG copolymers with HBPG and SiHBPG contents varying from 45 to 90 mol% and from 0.3 to 1.5 mol%, respectively. The copolymer abbreviations used here identify the percentage HBPG and SiHBPG contents. For example, PCL-73HBPG/1SiHBPG contains and 27mol.% PCL, 72 mol% HBPG and 1 mol% SiHBPG units. The copolymers were characterised by GPC, 1H NMR, TGA and DSC at the University of Bolton and using the HNMR and GPC facilities at the Institute of Polymers, Bulgarian Academy of Sciences . The PCL-HBPG/1SiHBPG polymers are amphiphilic and readily self-assemble in aqueous solutions into micelles composed of a hydrophobic PCL inner core and a surrounding shell of hydrophilic HBPG. At concentrations below the CMC the PCL-HBPG/1SiHBPG polymers are freely dispersed in water. To determine the CMC of the PCL-HBPG/1SiHBPG polymers in aqueous solution a previously described approach has been adopted utilising the nonpolar dye DPH, the absorption characteristics of which are sensitive to changes in its microenvironment. It shows minimal absorbance in water but a characteristic maximum at 356 nm is observed in a hydrophobic environment, such as upon solubilisation of DPH in the hydrophobic domains of the copolymer micelles. The CMC values were determined at four temperatures - 25, 37, 50 and 60 °C. The CMCs of the polymers were only slightly affected by temperature. To further explore the temperature behaviour of the aqueous solutions of the PCL-HBPG/1SiHBPG copolymers we investigated the variations of the transmittance of light with the temperature at concentrations above the CMC. The variations of the turbidity were strongly composition dependent. The solutions of the PCL-45HBPG/1SiHBPG, that is the copolymer with the lowest HBPG content, were opaque but homogeneous over the whole temperature range studied. For the PCL-90HBPG/1SiHBPG the variations of transmittance with temperature resemble those observed in the dilute aqueous solutions of the homo HBPG/1SiHBPG. The solutions remained transparent and showed no temperature variations over the whole temperature range. The absence of temperature induced changes in the PCL-90HBPG/1SiHBPG solutions could be related to the increasingly improved steric shielding of the hydrophobic backbone with the largest HBPG branches.
Collaborator Contribution The characterization of copolymer structure, composition and polydespersity utilizing 250 MHz Bruker WM 250 HNMR spectrometer and GPC, Waters system containing four Styragel columns with nominal pore sizes of 100, 500, 500 and 1000 Å fitted with a refractive index detector (R401) was carried out at the Institute of Polymers, Bulgarian Academy of Sciences, IP, BAS.The weight average molecular weight (Mw) and polydispersity indices (PDI) of the copolymers were determined by GPC . The copolymers had Mw ranging from 1 200 to 34 500 g/mol. GPC analyses gave monomodal or bimodal distributions with polydispersities of the low and high molecular weight fractions ranging from 1.15 to 1.25 and from 1.13 to 1.30, respectively. The copolymers' structural compositions were determined from their 1H NMR in D2O (IP, BAS). By using 1H NMR at the Institute of Polymers, Bulgarian Academy of Sciences, we were able to determine the copolymer's composition and to calculate the molar percentage contents of HBPG, PCL and silicon. GPC analysis (carried out at the IP, BAS) provided information regarding the weight average molecular weights of the copolymers and their dispersity. The Light Scattering analysis (carried out at the IP, BAS) provided an important information regarding the size of the copolymer's particles and the nature of their interactions with the solvent. The detailed characterization of the copolymers is essential in order to understand the effect of varying hydrophobicity and copolymer architecture on the morphology and mechanical properties of the PCL-HBPG/1SiHBPGgel scaffolds.
Impact The collaboration is interdisciplinary and involves partnerships between polymer chemists and materials scientists . The collaboration strengthens the international links between the UK and Bulgaria and will contribute to significant advances in understanding, methodology, theory and application of injectable scaffolds for treatment of tissue disorders. Based on the new knowledge and experience generated from the project the Institute of Polymers, Bulgarian Academy of Sciences will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research.
Start Year 2016
 
Description Investigation of the spontaneous self-assembly of PCL-HBPG/SIHBPG copolymers in water 
Organisation Bulgarian Academy of Sciences
Department Institute of Polymers
PI Contribution We have synthesized a series of thermo-responsive trimethoxysilane end-capped hyperbranched poly(glycidol)/poly(caprolactone) PCL-HBPG/SiHBPG copolymers of various compositions. The PCL-HBPG/SiHBPG copolymers were synthesised by anionic polymerization of a mixture of glycidol and 3-glycidyloxypropyl trimethoxysilane using partially deprotonated PCL diol with molecular weight of 2000 g/mol as a macroinitiator. A number- of polymerizations were carried out to prepare PCL-HBPG/SiHBPG copolymers with HBPG and SiHBPG contents varying from 45 to 90 mol% and from 0.3 to 1.5 mol%, respectively. The copolymer abbreviations used here identify the percentage HBPG and SiHBPG contents. For example, PCL-73HBPG/1SiHBPG contains and 27mol.% PCL, 72 mol% HBPG and 1 mol% SiHBPG units. The copolymers were characterised by GPC, 1H NMR, TGA and DSC at the University of Bolton and using the HNMR and GPC facilities at the Institute of Polymers, Bulgarian Academy of Sciences . The PCL-HBPG/1SiHBPG polymers are amphiphilic and readily self-assemble in aqueous solutions into micelles composed of a hydrophobic PCL inner core and a surrounding shell of hydrophilic HBPG. At concentrations below the CMC the PCL-HBPG/1SiHBPG polymers are freely dispersed in water. To determine the CMC of the PCL-HBPG/1SiHBPG polymers in aqueous solution a previously described approach has been adopted utilising the nonpolar dye DPH, the absorption characteristics of which are sensitive to changes in its microenvironment. It shows minimal absorbance in water but a characteristic maximum at 356 nm is observed in a hydrophobic environment, such as upon solubilisation of DPH in the hydrophobic domains of the copolymer micelles. The CMC values were determined at four temperatures - 25, 37, 50 and 60 °C. The CMCs of the polymers were only slightly affected by temperature. To further explore the temperature behaviour of the aqueous solutions of the PCL-HBPG/1SiHBPG copolymers we investigated the variations of the transmittance of light with the temperature at concentrations above the CMC. The variations of the turbidity were strongly composition dependent. The solutions of the PCL-45HBPG/1SiHBPG, that is the copolymer with the lowest HBPG content, were opaque but homogeneous over the whole temperature range studied. For the PCL-90HBPG/1SiHBPG the variations of transmittance with temperature resemble those observed in the dilute aqueous solutions of the homo HBPG/1SiHBPG. The solutions remained transparent and showed no temperature variations over the whole temperature range. The absence of temperature induced changes in the PCL-90HBPG/1SiHBPG solutions could be related to the increasingly improved steric shielding of the hydrophobic backbone with the largest HBPG branches.
Collaborator Contribution The X-ray scattering facilities in the HZG, Germany was utilized in order to conduct highly detailed studies that focus on determination of the size, shape and internal structure of the particles formed in aqueous solution from the HBPG/PCL copolymers. The influence of temperature, copolymer architecture and concentration upon the self-assembly process as well as the structure of the gel scaffolds was clarified. SAXS experiments were performed at 25 and 60 °C for PCL-HBPG/1SiHBPG copolymers at concentration ranges from 0.5 to 1g/ml. The data were analysed by the indirect Fourier transformation (IFT) method which as model independent approach requires minimal input information about the object structure (maximal diameter) and in the approximation of spherical like objects there all dimensions of similar magnitude.The scattering curves were converted into real space equivalents, pair distance distribution function, p(r). The scattering at zero angle, I(0), and the cross-sectional radius of gyration, Rg, were determined from the pair distance distribution functions assuming sherical core shell-geometry of the particles. Information on the weight-average molecular weights, Mw, the radii of gyration, Rg, and the second virial coefficients, A2 for the particles formed in the dilute aqueous solutions of PCL-HBPG/1SiHBPG polymers, was obtained from the Static Light Scattering data, SLS using a Light Scattering instrument available at the Institute of Polymers, Bulgarian Academyof Sciences, IP, BAS. The self-organised structures was visualised by TEM (IP, BAS). The new results allowed us to establish the relationship between particles' gel composition, porosity, biodegradability and mechanical properties.
Impact The results of this research were prepared for publication. One article titled: New Thrimetoxisilinated End-caped Hyper Branched Poly(glycidol)/Poly(caprolactam) (HBPG/PCL) Copolymers for Cell Delivery and Tissue Repair, C. Conzalez Chommon, Clara, V.Garamus, J. Ebdon, S. Rangelov, , Ch. Novakov, J. Hoyland and S. Halacheva is due to be submitted very soon to Macromolecules, an ACS journal: A second article is in preparation. Based on the new knowledge and experience generated from the project the HZG and the IP, BAS will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research. The collaboration is interdisciplinary and involves partnerships between polymer chemists and materials scientists . The collaboration strengthens the international links between the UK, Bulgaria and Germany and will contribute to significant advances in understanding, methodology, theory and application of injectable scaffolds for treatment of tissue disorders. Based on the new knowledge and experience generated from the project the HZG, Germany and IP, BAS will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research.
Start Year 2016
 
Description Investigation of the spontaneous self-assembly of PCL-HBPG/SIHBPG copolymers in water 
Organisation Helmholtz Association of German Research Centres
Department Helmholtz-Zentrum Geesthacht
Country Germany 
Sector Academic/University 
PI Contribution We have synthesized a series of thermo-responsive trimethoxysilane end-capped hyperbranched poly(glycidol)/poly(caprolactone) PCL-HBPG/SiHBPG copolymers of various compositions. The PCL-HBPG/SiHBPG copolymers were synthesised by anionic polymerization of a mixture of glycidol and 3-glycidyloxypropyl trimethoxysilane using partially deprotonated PCL diol with molecular weight of 2000 g/mol as a macroinitiator. A number- of polymerizations were carried out to prepare PCL-HBPG/SiHBPG copolymers with HBPG and SiHBPG contents varying from 45 to 90 mol% and from 0.3 to 1.5 mol%, respectively. The copolymer abbreviations used here identify the percentage HBPG and SiHBPG contents. For example, PCL-73HBPG/1SiHBPG contains and 27mol.% PCL, 72 mol% HBPG and 1 mol% SiHBPG units. The copolymers were characterised by GPC, 1H NMR, TGA and DSC at the University of Bolton and using the HNMR and GPC facilities at the Institute of Polymers, Bulgarian Academy of Sciences . The PCL-HBPG/1SiHBPG polymers are amphiphilic and readily self-assemble in aqueous solutions into micelles composed of a hydrophobic PCL inner core and a surrounding shell of hydrophilic HBPG. At concentrations below the CMC the PCL-HBPG/1SiHBPG polymers are freely dispersed in water. To determine the CMC of the PCL-HBPG/1SiHBPG polymers in aqueous solution a previously described approach has been adopted utilising the nonpolar dye DPH, the absorption characteristics of which are sensitive to changes in its microenvironment. It shows minimal absorbance in water but a characteristic maximum at 356 nm is observed in a hydrophobic environment, such as upon solubilisation of DPH in the hydrophobic domains of the copolymer micelles. The CMC values were determined at four temperatures - 25, 37, 50 and 60 °C. The CMCs of the polymers were only slightly affected by temperature. To further explore the temperature behaviour of the aqueous solutions of the PCL-HBPG/1SiHBPG copolymers we investigated the variations of the transmittance of light with the temperature at concentrations above the CMC. The variations of the turbidity were strongly composition dependent. The solutions of the PCL-45HBPG/1SiHBPG, that is the copolymer with the lowest HBPG content, were opaque but homogeneous over the whole temperature range studied. For the PCL-90HBPG/1SiHBPG the variations of transmittance with temperature resemble those observed in the dilute aqueous solutions of the homo HBPG/1SiHBPG. The solutions remained transparent and showed no temperature variations over the whole temperature range. The absence of temperature induced changes in the PCL-90HBPG/1SiHBPG solutions could be related to the increasingly improved steric shielding of the hydrophobic backbone with the largest HBPG branches.
Collaborator Contribution The X-ray scattering facilities in the HZG, Germany was utilized in order to conduct highly detailed studies that focus on determination of the size, shape and internal structure of the particles formed in aqueous solution from the HBPG/PCL copolymers. The influence of temperature, copolymer architecture and concentration upon the self-assembly process as well as the structure of the gel scaffolds was clarified. SAXS experiments were performed at 25 and 60 °C for PCL-HBPG/1SiHBPG copolymers at concentration ranges from 0.5 to 1g/ml. The data were analysed by the indirect Fourier transformation (IFT) method which as model independent approach requires minimal input information about the object structure (maximal diameter) and in the approximation of spherical like objects there all dimensions of similar magnitude.The scattering curves were converted into real space equivalents, pair distance distribution function, p(r). The scattering at zero angle, I(0), and the cross-sectional radius of gyration, Rg, were determined from the pair distance distribution functions assuming sherical core shell-geometry of the particles. Information on the weight-average molecular weights, Mw, the radii of gyration, Rg, and the second virial coefficients, A2 for the particles formed in the dilute aqueous solutions of PCL-HBPG/1SiHBPG polymers, was obtained from the Static Light Scattering data, SLS using a Light Scattering instrument available at the Institute of Polymers, Bulgarian Academyof Sciences, IP, BAS. The self-organised structures was visualised by TEM (IP, BAS). The new results allowed us to establish the relationship between particles' gel composition, porosity, biodegradability and mechanical properties.
Impact The results of this research were prepared for publication. One article titled: New Thrimetoxisilinated End-caped Hyper Branched Poly(glycidol)/Poly(caprolactam) (HBPG/PCL) Copolymers for Cell Delivery and Tissue Repair, C. Conzalez Chommon, Clara, V.Garamus, J. Ebdon, S. Rangelov, , Ch. Novakov, J. Hoyland and S. Halacheva is due to be submitted very soon to Macromolecules, an ACS journal: A second article is in preparation. Based on the new knowledge and experience generated from the project the HZG and the IP, BAS will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research. The collaboration is interdisciplinary and involves partnerships between polymer chemists and materials scientists . The collaboration strengthens the international links between the UK, Bulgaria and Germany and will contribute to significant advances in understanding, methodology, theory and application of injectable scaffolds for treatment of tissue disorders. Based on the new knowledge and experience generated from the project the HZG, Germany and IP, BAS will be able to develop new techniques and approaches for tissue repair and to establish complementary, parallel programmes for scientific research.
Start Year 2016
 
Description Attendance to a conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I have presented a poster to the RSC Biotechnology Group conference "Chemistry, Stem Cells and Regenerative Medicine" at the RSC Chemistry Centre,
Burlington House, London on 11 September 2017. The conference included presentations by key scientists and clinicians working at the forefront of stem cell research. The key scientists and clinicians discussed recent progress in this exciting field as well as future challenges involved in developing effective cell-based and non-cell-based therapeutics for tissue repair and regenerative medicine.
Year(s) Of Engagement Activity 2017
URL https://mxm.mxmfb.com/rsps/m/xIyQkBA-m9pQLc0siM5LhxtgPJieHYFciOdma4tYMCs
 
Description Attendance to an international conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact We (the PDRA and the Principal Investigator) have presented a poster to the 13th International Conference on Materials Chemistry (MC13) in Liverpool, UK.The soft matter and biomaterials themes of the conference focused on the relationship between the design and function of the biomaterials as well as their applications. Therefore, we considered that this subject area was appropriate for presenting our work. The conference was attended by academics, industrial and healthcare representatives. We were involved in networking with other scientists and health representatives working in the area of tissue engineering and reconstructive medicine in order to foster interdisciplinary collaboration and to facilitate the incorporation of the newly developed scaffold materials into commercial formulations .
Year(s) Of Engagement Activity 2017
URL http://www.rsc.org/events/detail/21273/13th-international-conference-on-materials-chemistry-mc13
 
Description Construction of an easily accessible web link to the project 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The key information of the projects and its updates has been uploaded online on the ResearchGate and Orchid web sites and a link to Linkedin has also been created. Our aim was to find more partners and supporters and to share the project updates with a wider audience. The project has 60 total reads and 13 followers within an audience of 394 researchers so far. We will continue to provide regular project updates by uploading data and images of material and biological testing.
Year(s) Of Engagement Activity 2017
URL https://www.researchgate.net/project/Multifunctional-Gel-Scaffolds-for-Cell-Delivery-and-Tissue-Repa...