Spiropyran (SP) is a mechanophore that undergoes changes in chemical structure and thus in optica... more Spiropyran (SP) is a mechanophore that undergoes changes in chemical structure and thus in optical character when subjected to a force. Incorporation of SP into polymer chains enables optical detec...
Poly(lactic-co-glycolic acid) (PLGA) is the most prevalent polymer drug delivery vehicle in use t... more Poly(lactic-co-glycolic acid) (PLGA) is the most prevalent polymer drug delivery vehicle in use today. There are about 20 commercialized drug products in which PLGA is used as an excipient. In more than half of these formulations, PLGA is used in the form of microparticles (with sizes in the range between 60 nm and 100 μm). The primary role of PLGA is to control the kinetics of drug release toward achieving sustained release of the drug. Unfortunately, most drug-loaded PLGA microparticles exhibit a common drawback: an initial uncontrolled burst of the drug. After 30 years of utilization of PLGA in controlled drug delivery systems, this initial burst drug release still remains an unresolved challenge. In this Review, we present a summary of the proposed mechanisms responsible for this phenomenon and the known factors affecting the burst release process. Also, we discuss examples of recent efforts made to reduce the initial burst release of the drug from PLGA particles.
Previous studies have shown that calcium tungstate (CaWO4) nanoparticles (NPs) can be used as a r... more Previous studies have shown that calcium tungstate (CaWO4) nanoparticles (NPs) can be used as a radiosensitizing/X-ray contrast agent for cancer treatment. However, due to the propensity of calcium...
Currently, there is great interest in the development of ways to achieve the benefits of radiatio... more Currently, there is great interest in the development of ways to achieve the benefits of radiation treatment with reduced negative effects. The present study demonstrates the utilization of Radio-Luminescent Particles (RLPs) as a means to achieve radio-sensitization/enhancement and their ability to affect head and neck cancer cell cultures (in vitro) and xenografts (in vivo). Our approach utilizes a naturally-abundant radio-luminescent mineral, calcium tungstate (CaWO 4) in its micro or nanoparticulate form for generating secondary UV-A light by γ ray/Xray photons. In vitro tests demonstrate that an un-optimized RLP materials (uncoated CaWO 4 (CWO) microparticles (MPs) and PEG-PLA-coated CWO nanoparticles (NPs)) induce a significant enhancement of the tumor suppressive effect of X-rays/γ rays in both radio-sensitive and radio-resistant cancer models; uncoated CWO MPs and PEG-PLA-coated CWO NPs demonstrate comparable radio-sensitization efficacy in vitro. Mechanistic studies reveal that concomitant CaWO 4 causes increased mitotic death in radio-resistant cells treated with radiation, whereas CaWO 4 sensitizes radio-sensitive cells to X-ray-induced apoptosis/necrosis. Radiosensitization efficacy of intratumorally injected CaWO 4 particles (uncoated CWO MPs and PEG-PLA-coated CWO NPs) is also evaluated in vivo in mouse head and neck cancer xenografts. Uncoated CWO MPs suppress tumor growth more effectively than PEG-PLA-coated CWO NPs. Based on theoretical considerations, an argument is proposed that uncoated CWO MPs release sub-toxic levels of tungstate ions, which cause increased effects of photoelectric electron emissions. The effect of folic acid functionalization on in vitro radio-sensitization behavior produced by PEG-PLA-coated CWO NPs is studied. Surface folic acid results in a significant improvement in radio-sensitization efficiency of CaWO 4 .
Polycations are used for a number of biological applications, including antibiotics and gene ther... more Polycations are used for a number of biological applications, including antibiotics and gene therapy. One aspect of the use of polycation gene carriers such as polyethylenemine (PEI) in gene therapy that is not well understood is their ability to escape from the vesicles they are internalized in. Here, in an attempt to gain a better understanding of PEI interaction with endosomal lipids under osmotic stress, we performed investigations using monolayers and vesicles derived from a mixture of neutral and negative lipids (1,2-dipalmitoylphosphatidylcholine (DPPC) and bis(monoacylglycero)phosphate (BMP), respectively). X-ray reflectivity (XR) and Langmuir trough measurements confirmed PEI adsorption to the negatively charged membrane. Confocal microscopy imaging indicated that PEI adsorption actually increases the overall integrity of the DPPC/BMP vesicle against osmotic stresses while also causing overall deformation and permeabilization of the lipid membrane, thus leading to leakage o...
Hepatitis B virus capsid (HBVC), a self-assembled protein nanoparticle comprised of 180 or 240 su... more Hepatitis B virus capsid (HBVC), a self-assembled protein nanoparticle comprised of 180 or 240 subunit proteins, is used as a cage for genetic encapsulation of fluorescent proteins (FPs). The self-quenching of FPs is controlled by varying the spacing between FPs within the capsid structure. Double-layered FP nanoparticle possessing cancer cell-targeting capabilities is also produced by additionally attaching FPs and cancer cell receptor-binding peptides (affibodies) to the outer surface of the capsid. The generically modified HBVC with double layers of mCardinal FPs and affibodies (mC-DL-HBVC) exhibit a high fluorescence intensity and a strong photostability, and is efficiently internalized by cancer cells and significantly stable against intracellular degradation. The mC-DL-HBVC effectively detects tumor in live mice with enhanced tumor targeting and imaging efficiency with far less accumulation in the liver, compared to a conventional fluorescent dye, Cy5.5. This suggests the great potential of mC-DL-HBVC as a promising contrast agent for in vivo tumor fluorescence imaging. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
X-ray computed tomography (CT) is currently one of the most powerful, non-invasive, clinical in v... more X-ray computed tomography (CT) is currently one of the most powerful, non-invasive, clinical in vivo imaging techniques, which has resulted from advances in both X-ray device and contrast enhancement technologies. The present study demonstrates, for the first time, that metal tungstates (such as CaWO4) are promising contrast agents for X-ray, radiation and CT imaging, because of the high X-ray mass attenuation of tungsten (W). We have developed a method of formulation, in which CaWO4 (CWO) nanoparticles (NPs) are encapsulated within a bio-compatible poly(ethylene glycol-b-D,L-lactic acid) (PEG-PLA) block copolymer (BCP) capsule. We show that these PEG-PLA-encapsulated CWO NPs (170 ± 10 nm hydrodynamic diameter) produce a higher CT contrast (by a factor of about 2) than commercial iodine-based radio-contrast agents (e.g., Iohexol) at identical molar concentrations of W or I atoms. PEG-PLA-coated CWO NPs are chemically stable and completely non-toxic. It was confirmed that the maximum...
The synthesis of poly(lactic acid), PLA, is facile in the presence of the cyclic, organic amidine... more The synthesis of poly(lactic acid), PLA, is facile in the presence of the cyclic, organic amidine catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene, DBU. Since DBU's catalytic capability was first reported by Lohmeijer and colleagues in 2006 for ring-opening polymerizations (ROP), there have been numerous studies conducted by a variety of groups on the catalytic functioning of DBU in the ROPs of cyclic esters resulting in a large body of un-unified material from a mechanistic standpoint. This lack of clarity will hamper engineering polymers with desired characteristics from cyclic ester and lactone monomers. The work outlined in this paper seeks to propose a unified picture of the mechanisms in the DBU catalyzed ROP of lactide. In providing this unified picture of the ROP our work encompassed: (i) proposing a detailed reaction network scheme, (ii) conducting syntheses of lactide and DBU over a range of initial concentrations, and (iii) kinetic modeling to further support the proposed reaction network. As a result, our work has produced: (i) kinetic data, (ii) a consistent, viable reaction scheme verified through kinetic modeling, (iii) deduced and quantified the interplay between polymerization routes facilitated by the presence of DBU, thus demonstrating the need for detailed kinetic studies to deconstruct complex reaction networks, (iv) the first experimental evidence in support of the combination of ketene aminalended chains with alcohol-ended chains, and (v) analyzed the robustness of the catalyst to acid contamination.
Recently, many theranostic nanomaterials have been developed by integrating therapeutic and diagn... more Recently, many theranostic nanomaterials have been developed by integrating therapeutic and diagnostic agents in a single regimen. Real-time visualization of nano drug carrier biodistributions, drug release processes and therapeutic responses can provide critical information needed for dynamically optimizing treatment operations in a personalized manner in real time. This review highlights recent progresses in the development of multifunctional nanoparticles possessing both therapeutic and imaging functionalities for cancer therapy. The advantages of using nanoparticle platforms are discussed. Examples demonstrating various combinations of imaging and therapeutic modalities are highlighted.
We present a theoretical study of the single-chain statistics and two-dimensional (2-D) phase beh... more We present a theoretical study of the single-chain statistics and two-dimensional (2-D) phase behavior of mixed brushes composed of charged and non-charged polymers. We extend the Edwards Hamiltonian formulation for the Green function to investigation of mixed brushes containing a polyelectrolyte species through the incorporation of the combined electrostatic effects as an additional external field which can be self-consistently computed
Langmuir : the ACS journal of surfaces and colloids, Jan 3, 2015
Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glyco... more Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) exhibit an exponential increase in surface pressure under high monolayer compression. In order to understand the molecular origin of this behavior, a combined experimental and theoretical investigation (including surface pressure-area isotherm, X-ray reflectivity (XR) and interfacial rheological measurements, and a self-consistent field (SCF) theoretical analysis) was performed on air-water monolayers formed by a PLGA-PEG diblock copolymer and also by a non-glassy analogue of this diblock copolymer, poly((D,L-lactic acid-ran-glycolic acid-ran-caprolactone)-block-ethylene glycol) (PLGACL-PEG). The combined results of this study show that the two mechanisms, i.e., the glass transition of the collapsed PLGA film and the lateral repulsion of the PEG brush chains that occur simultaneously under lateral compression of the monolayer, are both responsible for the observed PLGA-PEG ...
Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. No.99CH37015)
Cell-size vesicles were made from amphiphilic diblock copolymers and characterized by micromanipu... more Cell-size vesicles were made from amphiphilic diblock copolymers and characterized by micromanipulation. The average molecular weight of the base, synthetic polymer studied, polyethyleneoxide-polyethylethylene (EO40-EE37), is several-fold greater than that of usual phospholipids of biomembranes. Both the membrane bending and area expansion moduli of electroformed polymersomes (polymer-based liposomes) fell within the range of lipid membrane measurements, but the giant polymersome's membrane
Advances in colloid and interface science, Jan 14, 2015
Nanotechnology is a rapidly expanding field that has very promising applications that will improv... more Nanotechnology is a rapidly expanding field that has very promising applications that will improve industry, medicine, and consumer products. However, despite the growing widespread use of engineered nanoparticles in these areas, very little has been done to assess the potential health risks they may pose to high-risk areas of the body, particularly the lungs. In this review we first briefly discuss the structure of the lungs and establish that the pulmonary surfactant (PS), given its vulnerability and huge contribution to healthy lung function, is a mechanism of great concern when evaluating potential nanoparticle interactions within the lung. To warrant that these interactions can occur, studies on the transport of nanoaerols are reviewed to highlight that a plethora of factors contribute to a nanoparticle's ability to travel to the deep regions of the lung where PS resides. The focus of this review is to determine the extent that physicochemical characteristics of nanoparticl...
Poly(propylene carbonate) (PPC) is a plastic material that can be mass produced from naturally ab... more Poly(propylene carbonate) (PPC) is a plastic material that can be mass produced from naturally abundant carbon dioxide. This polymer is also known to decompose back to CO2 when heated above about 200 °C. Here we report that the CO2-generation temperature of PPC can be reduced down to the 40–80 °C range in aqueous environment by using a photoacid generator (PAG) as the catalyst for activating the random scission reaction of PPC. We also investigated the thermal degradation of a PPC-based amphiphilic block copolymer, poly(poly(ethylene glycol) methyl ether methacrylate)-poly(propylene carbonate)-poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA-PPC-PPEGMA). These triblock copolymers form stable small-sized (<200 nm) micelles in water. We found evidence that with the aid of added PAG these micelles can degrade under mild heating conditions (<80 °C), similarly to what is expected from PPC homopolymer experiments. The combined results suggest that PPC-based amphiphilic block copolymers might be of interest for applications in ultrasound contrast.
Spiropyran (SP) is a mechanophore that undergoes changes in chemical structure and thus in optica... more Spiropyran (SP) is a mechanophore that undergoes changes in chemical structure and thus in optical character when subjected to a force. Incorporation of SP into polymer chains enables optical detec...
Poly(lactic-co-glycolic acid) (PLGA) is the most prevalent polymer drug delivery vehicle in use t... more Poly(lactic-co-glycolic acid) (PLGA) is the most prevalent polymer drug delivery vehicle in use today. There are about 20 commercialized drug products in which PLGA is used as an excipient. In more than half of these formulations, PLGA is used in the form of microparticles (with sizes in the range between 60 nm and 100 μm). The primary role of PLGA is to control the kinetics of drug release toward achieving sustained release of the drug. Unfortunately, most drug-loaded PLGA microparticles exhibit a common drawback: an initial uncontrolled burst of the drug. After 30 years of utilization of PLGA in controlled drug delivery systems, this initial burst drug release still remains an unresolved challenge. In this Review, we present a summary of the proposed mechanisms responsible for this phenomenon and the known factors affecting the burst release process. Also, we discuss examples of recent efforts made to reduce the initial burst release of the drug from PLGA particles.
Previous studies have shown that calcium tungstate (CaWO4) nanoparticles (NPs) can be used as a r... more Previous studies have shown that calcium tungstate (CaWO4) nanoparticles (NPs) can be used as a radiosensitizing/X-ray contrast agent for cancer treatment. However, due to the propensity of calcium...
Currently, there is great interest in the development of ways to achieve the benefits of radiatio... more Currently, there is great interest in the development of ways to achieve the benefits of radiation treatment with reduced negative effects. The present study demonstrates the utilization of Radio-Luminescent Particles (RLPs) as a means to achieve radio-sensitization/enhancement and their ability to affect head and neck cancer cell cultures (in vitro) and xenografts (in vivo). Our approach utilizes a naturally-abundant radio-luminescent mineral, calcium tungstate (CaWO 4) in its micro or nanoparticulate form for generating secondary UV-A light by γ ray/Xray photons. In vitro tests demonstrate that an un-optimized RLP materials (uncoated CaWO 4 (CWO) microparticles (MPs) and PEG-PLA-coated CWO nanoparticles (NPs)) induce a significant enhancement of the tumor suppressive effect of X-rays/γ rays in both radio-sensitive and radio-resistant cancer models; uncoated CWO MPs and PEG-PLA-coated CWO NPs demonstrate comparable radio-sensitization efficacy in vitro. Mechanistic studies reveal that concomitant CaWO 4 causes increased mitotic death in radio-resistant cells treated with radiation, whereas CaWO 4 sensitizes radio-sensitive cells to X-ray-induced apoptosis/necrosis. Radiosensitization efficacy of intratumorally injected CaWO 4 particles (uncoated CWO MPs and PEG-PLA-coated CWO NPs) is also evaluated in vivo in mouse head and neck cancer xenografts. Uncoated CWO MPs suppress tumor growth more effectively than PEG-PLA-coated CWO NPs. Based on theoretical considerations, an argument is proposed that uncoated CWO MPs release sub-toxic levels of tungstate ions, which cause increased effects of photoelectric electron emissions. The effect of folic acid functionalization on in vitro radio-sensitization behavior produced by PEG-PLA-coated CWO NPs is studied. Surface folic acid results in a significant improvement in radio-sensitization efficiency of CaWO 4 .
Polycations are used for a number of biological applications, including antibiotics and gene ther... more Polycations are used for a number of biological applications, including antibiotics and gene therapy. One aspect of the use of polycation gene carriers such as polyethylenemine (PEI) in gene therapy that is not well understood is their ability to escape from the vesicles they are internalized in. Here, in an attempt to gain a better understanding of PEI interaction with endosomal lipids under osmotic stress, we performed investigations using monolayers and vesicles derived from a mixture of neutral and negative lipids (1,2-dipalmitoylphosphatidylcholine (DPPC) and bis(monoacylglycero)phosphate (BMP), respectively). X-ray reflectivity (XR) and Langmuir trough measurements confirmed PEI adsorption to the negatively charged membrane. Confocal microscopy imaging indicated that PEI adsorption actually increases the overall integrity of the DPPC/BMP vesicle against osmotic stresses while also causing overall deformation and permeabilization of the lipid membrane, thus leading to leakage o...
Hepatitis B virus capsid (HBVC), a self-assembled protein nanoparticle comprised of 180 or 240 su... more Hepatitis B virus capsid (HBVC), a self-assembled protein nanoparticle comprised of 180 or 240 subunit proteins, is used as a cage for genetic encapsulation of fluorescent proteins (FPs). The self-quenching of FPs is controlled by varying the spacing between FPs within the capsid structure. Double-layered FP nanoparticle possessing cancer cell-targeting capabilities is also produced by additionally attaching FPs and cancer cell receptor-binding peptides (affibodies) to the outer surface of the capsid. The generically modified HBVC with double layers of mCardinal FPs and affibodies (mC-DL-HBVC) exhibit a high fluorescence intensity and a strong photostability, and is efficiently internalized by cancer cells and significantly stable against intracellular degradation. The mC-DL-HBVC effectively detects tumor in live mice with enhanced tumor targeting and imaging efficiency with far less accumulation in the liver, compared to a conventional fluorescent dye, Cy5.5. This suggests the great potential of mC-DL-HBVC as a promising contrast agent for in vivo tumor fluorescence imaging. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
X-ray computed tomography (CT) is currently one of the most powerful, non-invasive, clinical in v... more X-ray computed tomography (CT) is currently one of the most powerful, non-invasive, clinical in vivo imaging techniques, which has resulted from advances in both X-ray device and contrast enhancement technologies. The present study demonstrates, for the first time, that metal tungstates (such as CaWO4) are promising contrast agents for X-ray, radiation and CT imaging, because of the high X-ray mass attenuation of tungsten (W). We have developed a method of formulation, in which CaWO4 (CWO) nanoparticles (NPs) are encapsulated within a bio-compatible poly(ethylene glycol-b-D,L-lactic acid) (PEG-PLA) block copolymer (BCP) capsule. We show that these PEG-PLA-encapsulated CWO NPs (170 ± 10 nm hydrodynamic diameter) produce a higher CT contrast (by a factor of about 2) than commercial iodine-based radio-contrast agents (e.g., Iohexol) at identical molar concentrations of W or I atoms. PEG-PLA-coated CWO NPs are chemically stable and completely non-toxic. It was confirmed that the maximum...
The synthesis of poly(lactic acid), PLA, is facile in the presence of the cyclic, organic amidine... more The synthesis of poly(lactic acid), PLA, is facile in the presence of the cyclic, organic amidine catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene, DBU. Since DBU's catalytic capability was first reported by Lohmeijer and colleagues in 2006 for ring-opening polymerizations (ROP), there have been numerous studies conducted by a variety of groups on the catalytic functioning of DBU in the ROPs of cyclic esters resulting in a large body of un-unified material from a mechanistic standpoint. This lack of clarity will hamper engineering polymers with desired characteristics from cyclic ester and lactone monomers. The work outlined in this paper seeks to propose a unified picture of the mechanisms in the DBU catalyzed ROP of lactide. In providing this unified picture of the ROP our work encompassed: (i) proposing a detailed reaction network scheme, (ii) conducting syntheses of lactide and DBU over a range of initial concentrations, and (iii) kinetic modeling to further support the proposed reaction network. As a result, our work has produced: (i) kinetic data, (ii) a consistent, viable reaction scheme verified through kinetic modeling, (iii) deduced and quantified the interplay between polymerization routes facilitated by the presence of DBU, thus demonstrating the need for detailed kinetic studies to deconstruct complex reaction networks, (iv) the first experimental evidence in support of the combination of ketene aminalended chains with alcohol-ended chains, and (v) analyzed the robustness of the catalyst to acid contamination.
Recently, many theranostic nanomaterials have been developed by integrating therapeutic and diagn... more Recently, many theranostic nanomaterials have been developed by integrating therapeutic and diagnostic agents in a single regimen. Real-time visualization of nano drug carrier biodistributions, drug release processes and therapeutic responses can provide critical information needed for dynamically optimizing treatment operations in a personalized manner in real time. This review highlights recent progresses in the development of multifunctional nanoparticles possessing both therapeutic and imaging functionalities for cancer therapy. The advantages of using nanoparticle platforms are discussed. Examples demonstrating various combinations of imaging and therapeutic modalities are highlighted.
We present a theoretical study of the single-chain statistics and two-dimensional (2-D) phase beh... more We present a theoretical study of the single-chain statistics and two-dimensional (2-D) phase behavior of mixed brushes composed of charged and non-charged polymers. We extend the Edwards Hamiltonian formulation for the Green function to investigation of mixed brushes containing a polyelectrolyte species through the incorporation of the combined electrostatic effects as an additional external field which can be self-consistently computed
Langmuir : the ACS journal of surfaces and colloids, Jan 3, 2015
Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glyco... more Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) exhibit an exponential increase in surface pressure under high monolayer compression. In order to understand the molecular origin of this behavior, a combined experimental and theoretical investigation (including surface pressure-area isotherm, X-ray reflectivity (XR) and interfacial rheological measurements, and a self-consistent field (SCF) theoretical analysis) was performed on air-water monolayers formed by a PLGA-PEG diblock copolymer and also by a non-glassy analogue of this diblock copolymer, poly((D,L-lactic acid-ran-glycolic acid-ran-caprolactone)-block-ethylene glycol) (PLGACL-PEG). The combined results of this study show that the two mechanisms, i.e., the glass transition of the collapsed PLGA film and the lateral repulsion of the PEG brush chains that occur simultaneously under lateral compression of the monolayer, are both responsible for the observed PLGA-PEG ...
Proceedings of the First Joint BMES/EMBS Conference. 1999 IEEE Engineering in Medicine and Biology 21st Annual Conference and the 1999 Annual Fall Meeting of the Biomedical Engineering Society (Cat. No.99CH37015)
Cell-size vesicles were made from amphiphilic diblock copolymers and characterized by micromanipu... more Cell-size vesicles were made from amphiphilic diblock copolymers and characterized by micromanipulation. The average molecular weight of the base, synthetic polymer studied, polyethyleneoxide-polyethylethylene (EO40-EE37), is several-fold greater than that of usual phospholipids of biomembranes. Both the membrane bending and area expansion moduli of electroformed polymersomes (polymer-based liposomes) fell within the range of lipid membrane measurements, but the giant polymersome&amp;#x27;s membrane
Advances in colloid and interface science, Jan 14, 2015
Nanotechnology is a rapidly expanding field that has very promising applications that will improv... more Nanotechnology is a rapidly expanding field that has very promising applications that will improve industry, medicine, and consumer products. However, despite the growing widespread use of engineered nanoparticles in these areas, very little has been done to assess the potential health risks they may pose to high-risk areas of the body, particularly the lungs. In this review we first briefly discuss the structure of the lungs and establish that the pulmonary surfactant (PS), given its vulnerability and huge contribution to healthy lung function, is a mechanism of great concern when evaluating potential nanoparticle interactions within the lung. To warrant that these interactions can occur, studies on the transport of nanoaerols are reviewed to highlight that a plethora of factors contribute to a nanoparticle's ability to travel to the deep regions of the lung where PS resides. The focus of this review is to determine the extent that physicochemical characteristics of nanoparticl...
Poly(propylene carbonate) (PPC) is a plastic material that can be mass produced from naturally ab... more Poly(propylene carbonate) (PPC) is a plastic material that can be mass produced from naturally abundant carbon dioxide. This polymer is also known to decompose back to CO2 when heated above about 200 °C. Here we report that the CO2-generation temperature of PPC can be reduced down to the 40–80 °C range in aqueous environment by using a photoacid generator (PAG) as the catalyst for activating the random scission reaction of PPC. We also investigated the thermal degradation of a PPC-based amphiphilic block copolymer, poly(poly(ethylene glycol) methyl ether methacrylate)-poly(propylene carbonate)-poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA-PPC-PPEGMA). These triblock copolymers form stable small-sized (<200 nm) micelles in water. We found evidence that with the aid of added PAG these micelles can degrade under mild heating conditions (<80 °C), similarly to what is expected from PPC homopolymer experiments. The combined results suggest that PPC-based amphiphilic block copolymers might be of interest for applications in ultrasound contrast.
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