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Representative micrographs of optical microscopy: O/W emulsion droplets formed from 4 (A) and their dried image after 3 days (B). Spheres formed from 4 and PBzMA composite (C) and its fluorescence micrograph (D). Scale bar: 10 m m for A, B and 15 m m for C and D.
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Water soluble star polymers consisting of a porphyrin center and four poly(oxazolines) arms such as Por-[poly(methyloxazoline)]4
(1), Por-[poly(ethyloxazoline)]4
(2), Por-[poly(methyloxazoline-co-ethyloxazoline)]4
(3) and Por-[poly(methyloxazoline)-b-poly(ethyloxazoline)]4
(4) were synthesized and used for the investigation of their unusual behavio...
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Citations
... The last option is the use of initiators with multiple electrophilic moieties, resulting in the formation of (star-shaped) polymers where the initiation site is at the core of the polymers, rather than the end. For this purpose, several multifunctional initiators have been developed based on alkyl chains [86][87][88][89][90], unsaturated groups, such as alkene [59,[90][91][92], acetylene [64,93], aromatic rings with two or more reactive sites [59,94], or tetrachloro-or iodo initiators from porphyrin [95]. While a great variety of cores has been used, it should be noted that fast initiation is required to obtain well-defined polymers. ...
The design and synthesis of macromolecules, i.e. macromolecular engineering, employ specific synthetic tools for the control over the functionality, topology, and composition of a macromolecule. In terms of macromolecular engineering, 2‐oxazolines present an attractive monomer class for the design of a structurally diverse set of macromolecules, as a wide array of monomer structures can be prepared via established synthetic pathways and macromolecules have been prepared from this monomer by cationic ring‐opening, zwitterionic, anionic, and radical polymerization techniques. Most prominently applied, however, is the cationic ring‐opening polymerization, since it is compatible with a wide range of 2‐oxazoline monomers and the living polymerization mechanism allows excellent control over the macromolecular architecture throughout the different steps of the polymerization. Furthermore, the obtained poly(2‐alkyl/aryl‐2‐oxazoline)s (PAOx) display excellent physical and chemical stability, as well as an overall biocompatible nature. These factors combined have led to a recent rise in popularity of PAOx as a highly modular polymer platform in biomedicine, where cutting‐edge macromolecular engineering is applied to face current challenges in biomedicine. In this article, the current state and opportunities in the macromolecular engineering of PAOx are discussed in great detail, thereby providing an overview of the developed synthetic methodologies to control their functionality, topology, and composition.
... A well-defined PEtOx offers a number of advantages such as low toxicity, good hydrophilicity, flexibility, and biocompatibility and has been approved by the U.S. Food and Drug Administration as an indirect additive used in food contact substances and has extensive application areas. PEtOx can be easily prepared by cationic ring-opening polymerization (CROP) in a controlled manner [17][18][19][20] of 2-ethyl 2-oxazoline monomers with various functional end groups by using functional terminating agents [21] and initiators [22][23][24] . ...
Liposome surface modifications serve great potential applications of liposomes, for instance, increasing stability, bioactive liposome conjugates, and targeted drug, gene, and image agent delivery. In this study, novel targeted lipopolymers, peptide 18/peptide 563-poly(2-ethyl-2-oxazoline)-dioleoylphosphatidyl-ethanolamine (P18/P563-PEtOx-DOPE), have been demonstrated to be successfully synthesized. The structures of P18/P563-PEtOx-DOPE were confirmed by FT-IR spectroscopy, GPC, and ¹H-NMR. In this strategy, poly(2-ethyl 2-oxazoline)-modified liposomes were firstly constructed with molecular weights of 3,500 and 5,800 Da. Then, we chose PEtOx5800-DOPE because it has been obtained better particle size (88.74 ± 0.6816) according to the DLS results. Then, peptides- and dye-PEtOx lipid-based nanovesicle (LN) were prepared by peptide-18, peptide-563, and 7-mercapto-4-methyl coumarin. Genetic material (pDNA) was encapsulated into the liposomes and evaluated the encapsulation of plasmid DNA with migration by using agarose gel electrophoresis. In vitro cytotoxicity experiment results on prostate cancer and breast cancer cell lines, parallelly with the healthy prostate (PNT1A) and breast (MCF10A) epithelial cell lines, cells showed insignificant toxic effects. Thus, we can suggest a novel PEtOx phospholipid thanks to this article and its integration with ligands, which great potential for gene transfer system.
... Conversely, the phosphazene-PMeOx star polymer showed no evidence for micellisation over a range of polymer concentrations suggesting the stars existed as unimolecular nanoparticles. In an alternative approach to inorganic hybrid materials, the hydrophilic/hydrophobic ratio of porphyrin initiated PMeOx and PMEOx-b-PEtOx star polymers was exploited to form an emulsion, the droplets of which were used as templates for the sol-gel polymerisation of tetraethylsilane (TEOS) [205,206]. Porphyrin initiated copolymerisation of PhOx and MeOx yielded star copolymers which were shown to form vesicular aggregates in aqueous solutions containing DMF (20%) [207]. Cationic equivalents were obtained by acidolysis of the PMeOx corona to furnish PEI-containing star copolymers [208]. ...
Poly(2-oxazoline)s (POx) are a class of polymers with tremendous potential for biomedical applications. The straightforward access to side and main chain functionalities by selecting suitable monomers and initiators/terminating agents, respectively, in combination with the biocompatibility, stealth and protein repellent properties of their water-soluble homologues enables the fabrication of highly functional POx materials. Post polymerisation modifications of POx further increase this toolbox and allow to merge their properties with the ones of other polymer classes. This review describes nano- and microscale POx particulate materials available to date with particular focus on macromolecular design of the polymers used for the individual formulation techniques. Amongst others, microparticles, microspheres, hollow layer-by-layer microcapsules as well as nanoparticles, micelles, polymersomes, nanogels and POx coated inorganic nanoparticles will be discussed.
... In the case of core-first strategies, a core molecule or a multifunctional initiator is synthesized or modified with initiating groups applicable for controlled polymerization reactions. In the literature, different examples of atom transfer radical polymerization (4,5) , reversible addition fragmentation chain transfer (6) , anionic ring-opening polymerization (7,8) , or cationic ring-opening polymerization (CROP) (9,10) are reported. One clear disadvantage of the core-first approach is that complete initiation is often difficult to verify and lower arm numbers are found when compared to initiation sites. ...
We demonstrate the synthesis of star-shaped poly(2-ethyl-2-oxazoline) featuring a porphyrin core starting from alkyne-functionalized porphyrin ([TPP-TB]4) and azide-functionalized poly(2-ethyl-2-oxazoline) (PEtOx-N3) via copper-catalyzed azide-alkyne cycloaddition (CuAAC). The porphyrin core was further utilized for the complexation of either copper or iron within the central cavity. The obtained materials were investigated using a combination of nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, size-exclusion chromatography, and matrix assisted laser desorption/ionization time-of-flight mass spectrometry. In the case of copper, the inclusion of the metal ion was achieved in a one-pot reaction during the CuAAC reaction for attaching the PEtOx-N3 arms.
... Several works by Jin are devoted to poly(oxazoline) stars with porphyrin center and 4 arms. He studied the influence of the fabrication method on the size of micelles of poly(phenyloxazoline-blockmethyloxazoline) in water/DMF mixtures [15] and suggested a procedure for assembly of (co)poly(2-alkyl-2-oxazoline)s star in water/chloroform emulsion [16]. Besides, selfo r g a n i z a t i o n o f p o l y ( p h e n y l o x a z o l i n e -b l o c kmethyloxazoline) star was observed when sphere aggregates became network-like aggregates and formed a vesicular tube after 3-week aging [17]. ...
Eight-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx) with calix[8]arene core (M ≈ 20,000 g mol−1) was studied by turbidimetry and light scattering in aqueous solutions within concentration c ranging from 0.002 to 0.19 g cm−3. The lower critical solution temperature (LCST) for PiPrOx is about 10 °C lower than for the linear analog. PiPrOx forms two types of particles at room temperature. The specie responsible for the fast mode is single macromolecules or 2–3 ones joined in aggregate with a hydrodynamic radius of 4.9 nm, irrespective of concentration. On heating, at first, growth of a large aggregate fraction was observed without variation of their hydrodynamic radii R
h(s). Then, R
h(s) increased up to 800 nm at c = 0.002 g cm−3, while the fast mode disappeared. At all concentrations, the third middle mode with a size ranging from 9 to 40 nm was registered. It was observed in a very narrow temperature interval near the cloud point. The hydrodynamic radii of species and their fraction in solution were monitored as a function of time after the change in temperature.
... Poly(2oxazoline)s are synthesized by living cationic ring-opening polymerization of 2-substituted-2-oxazolines and physicochemical properties depend on the substituent in the oxazoline ring, as well as the macromolecular structure and composition (17)(18)(19). In order to modify the properties and further enlarge the area of potential applications of poly (2oxazolines), the efforts are directed towards the synthesis of various block and star copolymers, segmented copolymer networks (also known as conetworks), and so on (20)(21)(22)(23). However, the use of poly(2-alkyl-2-oxazolines) in drug delivery so far is not well covered, and the research is focused mainly on the systems which increase the solubility of hydrophobic drugs. ...
Segmented copolymer networks (SCN) based on poly(2-ethyl-2-oxazoline) and containing 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and/or methyl methacrylate segments have been evaluated as potential sustained release systems of the water soluble cardioselective β-blocker metoprolol tartrate. The structure and properties of the drug carriers were investigated by differential scanning calorimetry, attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. Swelling kinetics of SCNs in various media was followed, and the conditions for effective MT loading were specified. MT-loaded SCNs with drug content up to 80 wt.% were produced. The release kinetics of metoprolol tartrate from the systems was studied and it was shown that the conetworks of different structure and composition are able to sustain the metoprolol tartrate release without additional excipients.
... Water-soluble polyoxazolines have been studied for various biomedical applications, because of their amphiphilic and self-assembling nature [114][115][116][117]. These polymers, with various chemical functionalities and architectures, can be synthesized by cationic ring-opening polymerization in a controlled manner [116,[118][119][120]. Poly(2-methyl-2-oxazoline) (PMOZ)-and poly(2-ethyl-2-oxazoline) (PEOZ)-linked DSPE (8) have been investigated for surface modification of liposomes as an alternative to PEG-DSPE [121]. ...
Liposomes are used as a delivery vehicle for drug molecules and imaging agents. The major impetus in their biomedical applications comes from the ability to prolong their circulation half-life after administration. Conventional liposomes are easily recognized by the mononuclear phagocyte system and are rapidly cleared from the blood stream. Modification of the liposomal surface with hydrophilic polymers delays the elimination process by endowing them with stealth properties. In recent times, the development of various materials for surface engineering of liposomes and other nanomaterials has made remarkable progress. Poly(ethylene glycol)-linked phospholipids (PEG-PLs) are the best representatives of such materials. Although PEG-PLs have served the formulation scientists amazingly well, closer scrutiny has uncovered a few shortcomings, especially pertaining to immunogenicity and pharmaceutical characteristics (drug loading, targeting, etc.) of PEG. On the other hand, researchers have also begun questioning the biological behavior of the phospholipid portion in PEG-PLs. Consequently, stealth lipopolymers consisting of non-phospholipids and PEG-alternatives are being developed. These novel lipopolymers offer the potential advantages of structural versatility, reduced complement activation, greater stability, flexible handling and storage procedures and low cost. In this article, we review the materials available as alternatives to PEG and PEG-lipopolymers for effective surface modification of liposomes.
... In contrast, the nature and characteristics of crystalline structure of linear PEI have not been exploited for materials application, due to that the selfassembled information programmed in the crystalline structure of linear PEI has not been discovered until our recent findings (). Our interest in linear PEI started from our studies on the synthesis, micelle/vesicle/ emulsion self-assembly and silica-based hybrid materials of chain-architecture-controlled polyoxazolines (Jin, 2002a; 2002b; 2003a; 2003b; 2003c; 2004). For example, star architecture consisting of a small benzene core and densely-six-armed poly(methyloxazoline) has been observed to be able to self-assemble in situ into a superstructured colloidal crystalline polymer in the reaction solution (Jin, 2003b). ...
... [26] Star-shaped poly(2-oxazoline)s have been prepared by the 'core-first' method using a wide range of multifunctional electrophilic initiators based on, e.g. cyclotriphosphazine, [27] silesquioxane, [28] porphyrin, [29][30][31] triphenylene, [32] bipyridine metal complex, [33,34] tetrabromoallyl, [35] and pluritriflate initiators. [36] In contrast, there are, to the best of our knowledge, only two examples using the 'arm-first' approach to prepare star-shaped poly(2-oxazoline)s with a defined number of arms. ...
... When the molar mass was decreased below 10000 g mol À1 , T CP was no longer observed for linear PEtOx in ambient liquid water. [29,30] The T CP of the star-PEtOx was found to remain almost constant around 908C, independent of the polymer molar mass, which is in contrast to the strong molar mass dependency for the linear analogues (Fig. 5, right). This significant difference is proposed to be due to the architecture of the star-shaped polymer, which suppresses polymer chain interactions that are responsible for lowering the T CP of linear polymers. ...
The synthesis of star-shaped poly(2-ethyl-2-oxazoline) is reported by direct end-capping of the living polymer chains with dendritic multiamines. The end-capping kinetics after addition of a first generation polypropylenimine dendrimer are discussed based on monitoring by size exclusion chromatography, revealing less efficient end-capping with larger poly(2-ethyl-2-oxazoline) chains and increasing dendrimer generation. In addition, it is demonstrated that the solution viscosity and cloud point temperature of the star-shaped polymers are much less affected by chain length compared with their linear analogues.
... Several porphyrin polymers have been synthesized [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Micellization of these polymers offers the opportunity to organize the nanostructure of dyes in solution. ...
... Attempts to synthesize polymers containing free-base porphyrin using ATRP was unsuccessful, because Cu(II) (formed by the Cu(I) 2 International Journal of Polymer Science catalyst) will preferentially insert into the porphyrin core [14,16]. Although metalloporphyrin polymers possess many interesting properties for applications, such as catalysis, light harvesting, oxygen transportation [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], and so on, other increasingly studied applications, such as sensors [18], prefer free-base porphyrin polymers. In our self-assembly research, free-base porphyrin polymers with optical sensitivity to external ions will be useful in probing aggregate structures. ...
Reversible addition fragmentation chain transfer (RAFT) synthesis and self-assembly of free-base porphyrin cored star polymers are reported. The polymerization, in the presence of a free-base porphyrin cored chain transfer agent (CTA-FBP), produced porphyrin star polymers with controlled molecular weights and narrow polydispersities for a number of monomers including N, N-dimethylacrylamide (DMA) and styrene (St). Well-defined amphiphilic star block copolymers, P-(PS-PDMA)4 and P-(PDMA-PS)4 (P: porphyrin), were also prepared and used for self-assembly studies. In methanol, a selective solvent for PDMA, spherical micelles were observed for both block copolymers as characterized by TEM. UV-vis studies suggested star-like micelles were formed from P-(PS-PDMA)4, while P-(PDMA-PS)4 aggregated into flower-like micelles. Spectrophotometric titrations indicated that the optical response of these two micelles to external ions was a function of micellar structures. These structure-related properties will be used for micelle studies and functional material development in the future.
