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Rajbanshi A, Mahmoudi N, Murnane D, Pavlova E, Slouf M, Dreiss C, Cook M. Combining branched copolymers with additives generates stable thermoresponsive emulsions with in situ gelation upon exposure to body temperature. Int J Pharm 2023; 637:122892. [PMID: 37001832 DOI: 10.1016/j.ijpharm.2023.122892] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/12/2023] [Accepted: 03/23/2023] [Indexed: 04/03/2023]
Abstract
Branched copolymer surfactants (BCS) containing thermoresponsive polymer components, hydrophilic components, and hydrophobic termini allow the formation of emulsions which switch from liquid at room temperature to a gel state upon heating. These materials have great potential as in situ gel-forming dosage forms for administration to external and internal body sites, where the emulsion system also allows effective solubilisation of a range of drugs with different chemistries. These systems have been reported previously, however there are many challenges to translation into pharmaceutical excipients. To transition towards this application, this manuscript describes the evaluation of a range of pharmaceutically-relevant oils in the BCS system as well as evaluation of surfactants and polymeric/oligomeric additives to enhance stability. Key endpoints for this study are macroscopic stability of the emulsions and rheological response to temperature. The effect of an optimal additive (methylcellulose) on the nanoscale processes occurring in the BCS-stabilised emulsions is probed by small-angle neutron scattering (SANS) to better comprehend the system. Overall, the study reports an optimal BCS/methylcellulose system exhibiting sol-gel transition at a physiologically-relevant temperature without macroscopic evidence of instability as an in situ gelling dosage form.
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Kessel S, Thakar N, Jia Z, Wolvetang EJ, Monteiro MJ. GRGD‐decorated three‐dimensional nanoworm hydrogels for culturing human embryonic stem cells. ACTA ACUST UNITED AC 2019. [DOI: 10.1002/pola.29342] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Stefanie Kessel
- Australian Institute for Bioengineering and NanotechnologyThe University of Queensland Brisbane 4072 Queensland Australia
| | - Nilay Thakar
- Australian Institute for Bioengineering and NanotechnologyThe University of Queensland Brisbane 4072 Queensland Australia
| | - Zhongfan Jia
- Australian Institute for Bioengineering and NanotechnologyThe University of Queensland Brisbane 4072 Queensland Australia
| | - Ernst J. Wolvetang
- Australian Institute for Bioengineering and NanotechnologyThe University of Queensland Brisbane 4072 Queensland Australia
| | - Michael J. Monteiro
- Australian Institute for Bioengineering and NanotechnologyThe University of Queensland Brisbane 4072 Queensland Australia
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Colloidal thermoresponsive gel forming hybrids. J Colloid Interface Sci 2010; 349:527-36. [DOI: 10.1016/j.jcis.2010.05.080] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 05/23/2010] [Accepted: 05/25/2010] [Indexed: 11/20/2022]
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Thermally-triggered gelation of PLGA dispersions: Towards an injectable colloidal cell delivery system. J Colloid Interface Sci 2010; 344:61-9. [DOI: 10.1016/j.jcis.2009.12.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 12/12/2009] [Accepted: 12/15/2009] [Indexed: 11/18/2022]
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Liu R, Saunders BR. Thermoresponsive surfaces prepared using adsorption of a cationic graft copolymer: a versatile method for triggered particle capture. J Colloid Interface Sci 2009; 338:40-7. [PMID: 19545877 DOI: 10.1016/j.jcis.2009.05.073] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2009] [Revised: 05/28/2009] [Accepted: 05/29/2009] [Indexed: 10/20/2022]
Abstract
In this study we investigate triggered particle capture at substrates containing adsorbed thermally responsive graft copolymers. The copolymers used were PDMA(x)(+)-g-(PNIPAm(n))(y), where DMA(+) is quaternized N,N-dimethylaminoethyl methacrylate and NIPAm is N-isopropylacrylamide. The x and y values originate from the macroinitiator used for copolymer preparation. In this study the copolymers are adsorbed onto two different substrates: quartz microscope slides and microporous, high surface area carbon foam. The substrates were coated with a layer of calcined laponite. The laponite acted as a conditioning layer and promoted strong adsorption of the copolymer. The hydrophobicity of the thermoresponsive surfaces was probed using variable-temperature contact angle measurements. The contact angles generally increased considerably upon increasing the temperature to above the lower critical solution temperature (LCST) of the copolymers. The ability of the thermoresponsive surfaces to capture dispersed particles was investigated using anionic and cationic polystyrene (PS) particles. PDMA(30)(+)-g-(PNIPAm(210))(14) was the most effective copolymer in terms of providing high capture efficiencies of anionic PS particles using temperature as the trigger. The thermoresponsive surfaces strongly held the anionic PS particles even when cooled to below the LCST. The relationships between copolymer structure and particle capture efficiency are discussed. The new approach used here for preparation thermoresponsive surfaces is potentially scalable to high volume applications.
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Affiliation(s)
- R Liu
- Polymer Science and Technology Group, The School of Materials, Materials Building, The University of Manchester, Grosvenor Street, M1 7HS, UK
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Liu R, Cellesi F, Tirelli N, Saunders B. A study of thermoassociative gelation of aqueous cationic poly(N-isopropyl acrylamide) graft copolymer solutions. POLYMER 2009. [DOI: 10.1016/j.polymer.2009.01.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Liu R, Tirelli N, Cellesi F, Saunders BR. Temperature-triggered gelation of aqueous laponite dispersions containing a cationic poly(N-isopropyl acrylamide) graft copolymer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:490-496. [PMID: 19115874 DOI: 10.1021/la802941h] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In this work, temperature-triggered gelation of aqueous laponite dispersions containing a cationic poly(N-isopropylacrylamide) (PNIPAm) graft copolymer was investigated. The copolymer used was PDMA(+)(30)-g-(PNIPAm(210))(14) [Liu et al. Langmuir 2008, 24, 7099]. DMA(+) is quarternarized N,N-dimethylaminoethyl methacrylate. The presence of small concentrations of laponite enabled temperature-triggered gel formation to occur at low copolymer concentrations (e.g., 1 wt %). Dynamic rheological measurements of the gels showed that they had storage modulus values of up to 400 Pa when the total solid volume fraction (polymer and laponite) was only about 0.02. The storage modulus was dependent on both the temperature and the composition of the dispersion used for preparation. The key component that provided the temperature-triggered gels with their elasticity was found to be self-assembled nanocomposite (NC) sheets. These NC sheets spontaneously formed at room temperature upon addition of laponite to the copolymer solution. The NC sheets had lateral dimensions on the order of hundreds of micrometers and a thickness of a few micrometers. The NC sheets were present within the temperature-triggered gels and formed elastically effective chains. The NC sheets exhibited temperature-triggered contraction with a contraction onset temperature of 27 degrees C. A conceptual model is proposed to qualitatively explain the relationship between gel elasticity and dispersion composition.
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Affiliation(s)
- R Liu
- Polymer Science and Technology Group, The School of Materials, The University of Manchester, Grosvenor Street, M1 7HS, UK
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Hui D, Nawaz M, Morris DP, Edwards MR, Saunders BR. Study of pH-triggered heteroaggregation and gel formation within mixed dispersions. J Colloid Interface Sci 2008; 324:110-7. [DOI: 10.1016/j.jcis.2008.05.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 05/16/2008] [Accepted: 05/19/2008] [Indexed: 11/28/2022]
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Liu R, De Leonardis P, Cellesi F, Tirelli N, Saunders BR. Cationic temperature-responsive poly(N-isopropyl acrylamide) graft copolymers: from triggered association to gelation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:7099-7106. [PMID: 18547094 DOI: 10.1021/la8002756] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In this work temperature-triggered association and gel formation within aqueous solutions of a new family of cationic poly( N-isopropyl acrylamide) (PNIPAm) graft copolymers have been investigated. Five copolymers were synthesized using aqueous atom transfer radical polymerization (ATRP) involving a macroinitiator based on quaternarized N, N-dimethylaminoethyl methacrylate units (DMA+). The PDMA+) x - g-(PNIPAmn)y copolymers have x and y values that originate from the macroinitiator; values for n correspond to the PNIPAm arm length. The copolymer solutions exhibited temperature-triggered formation of nanometer-sized aggregates at the cloud point temperature, which was 33-34 degrees C. The aggregates were investigated using variable-temperature turbidity, hydrodynamic diameter, and electrophoretic mobility measurements. The aggregates were clearly evident using SEM and flowerlike or spherical morphologies were observed. Variable-temperature electrophoretic mobility measurements revealed that the zeta potentials of the aggregates increased with DMA+ content. A study of the effect of added NaNO3 showed that electrostatic interactions controlled the size of the aggregates. The concentrated graft copolymer solutions showed temperature-triggered gelation when the copolymer concentrations exceeded 5 wt %, Fluid-to-gel phase diagrams were constructed. It was found that electrostatic interactions also controlled the gelation temperature. A correlation was found between aggregate size and the minimum copolymer concentration needed to form a gel. A mechanism for the temperature-triggered structural changes leading to the formation of aggregates (in dilute solution) or gels (in concentrated solutions) is proposed.
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Affiliation(s)
- R Liu
- Polymer Science and Technology Group, The School of Materials, The University of Manchester, Grosvenor Street, M1 7HS, UK
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Saunders JM, Saunders BR. Temperature‐Triggered Capture of Dispersed Particles Using a Laponite‐Poly(NIPAM) Temperature‐Responsive Surface. J MACROMOL SCI B 2007. [DOI: 10.1080/00222340701257877] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
| | - Brian R. Saunders
- a School of Materials, The University of Manchester , Manchester, UK
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Saunders JM, Alava C, Saunders BR. Temperature-Triggered Modification of Polymer- Solvent Interactions: From Fluid-to-Gel Transitions to Particle Capture. ACTA ACUST UNITED AC 2007. [DOI: 10.1002/masy.200750509] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Alava C, Saunders BR. Polymer stabilisers for temperature-induced dispersion gelation: Versatility and control. J Colloid Interface Sci 2006; 293:93-100. [PMID: 16023128 DOI: 10.1016/j.jcis.2005.06.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2005] [Revised: 06/03/2005] [Accepted: 06/09/2005] [Indexed: 11/16/2022]
Abstract
In this study the temperature-induced gelation of butadiene-acrylonitrile latex containing the added temperature-responsive polymer surfactant, poly(NIPAM-co-PEGMa) is investigated for the first time. (NIPAM and PEGMa are N-isopropylacrylamide and poly(ethylene glycol)methacrylate, respectively.) The results are compared with temperature-induced gelation of oil-in-water emulsions containing 1-bromohexadecane. The effect of added anionic surfactant, NaDBS (sodium dodecylbenzene sulfonate) on the temperature-induced gelation process and mechanism is considered. It was found that the gelation temperature (T(gel)) for the latex occurs at the cloud point temperature (T(cpt)) of the polymer and that T(gel) is much less affected by added NaDBS than is the case for emulsion gelation. The mathematical predictive theory recently derived for temperature-induced emulsion gelation was applied to the latex data and gave a good fit (i.e., T(gel) approximately 1/C(p), where C(p) is the concentration of added poly(NIPAM-co-PEGMa)). However, the causes for the variation of T(gel) with C(p) for temperature-induced latex and emulsion gelation are different. The variation of T(gel) for latex gelation in the presence of added NaDBS originates from surfactant association with poly(NIPAM-co-PEGMa) which increased T(cpt). In the case of emulsion gelation there are electrostatic interactions above T(cpt) which control T(gel). The subtle difference in the temperature-induced latex gelation mechanism is a consequence of the very high latex surface area (cf. emulsion), small inter-particle separation and the presence of electrolyte. The reason that T(gel) follows 1/C(p) for the latex is due to a fortuitous T(cpt) approximately 1/C(p) relationship that applies for poly(NIPAM-co-PEGMa) solution in the presence of NaDBS. The work presented here shows that addition of poly(NIPAM-co-PEGMa) to dispersions gives a versatile method for temperature-triggered gelation. Furthermore, the theory presented provides a framework for predicting their gelation temperatures.
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Affiliation(s)
- Cristina Alava
- School of Materials, The University of Manchester, Grosvenor Street, Manchester M1 7HS, UK
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Alava C, Saunders BR. Temperature-responsive emulsions: The effect of added surfactant. Colloids Surf A Physicochem Eng Asp 2005. [DOI: 10.1016/j.colsurfa.2005.05.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Koh AYC, Saunders BR. Small-angle neutron scattering study of temperature-induced emulsion gelation: the role of sticky microgel particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:6734-41. [PMID: 16008382 DOI: 10.1021/la050600h] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In this work, small-angle neutron scattering (SANS) is used to probe the structural transformations that accompany temperature-induced gelation of emulsions stabilized by a temperature-responsive polymer. The latter is poly(NIPAM-co-PEGMa) (N-isopropylacrylamide and poly(ethyleneglycol) methacrylate) and contains 86 mol% NIPAM. Turbidity measurements revealed that poly(NIPAM-co-PEGMa) has a lower critical solution temperature (T(LCST)) of 36.5 degrees C in D(2)O. Aqueous polymer solutions were used to prepare perfluorodecalin-in-water emulsions (average droplet size of 6.9 mum). These emulsions formed gels at 50 degrees C. SANS measurements were performed on the poly(NIPAM-co-PEGMa) solutions and emulsions as a function of temperature. The emulsion was also prepared using a D2O/H2O mixture containing 72 vol% D2O in order to make scattering from the droplets negligible (on-contrast). The SANS data were analyzed using a combination of Porod and Ornstein-Zernike form factors. The results showed that the correlation length (xi) of the polymer scaled as xi approximately phi(p)(-0.68) at 32 degrees C, where phi(p) is the polymer volume fraction. The xi value increased for all systems as the temperature increased, which was attributed to a spinodal transition. At temperatures greater than T(LCST), the polymer solution changed to a polymer dispersion of poly(NIPAM-co-PEGMa) aggregates. The aggregates have features that are similar to microgel particles. The average size of these particles was estimated as 160-170 nm. The particles are "sticky" and are gel-forming. The on-contrast experiments performed using the emulsion indicated that the interfacial polymer chains condensed to give a relatively thick polymer layer at the perfluorodecalin-water interface at 50 degrees C. The gelled emulsions appear to consist of perfluorodecalin droplets with an encapsulating layer of collapsed polymer to which sticky microgel particles are adsorbed. The latter act as a "glue" between coated droplets in the emulsion gel.
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Affiliation(s)
- Andrew Y C Koh
- Department of Chemistry, University of Adelaide, SA, 5005 Australia
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