Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• and drug delivery systems [12]. pH-Responsive molecular tweezers A particular case of coordination-responsive systems is when a proton is used as a stimulus leading to pH-responsive systems with the protonation/deprotonation of the switchable moiety. The conformational switch in these systems is

Facile access to pyridinium-based bent aromatic amphiphiles: nonionic surface modification of nanocarbons in water

• Lorenzo Catti,
• Shinji Aoyama and
• Michito Yoshizawa

Beilstein J. Org. Chem. 2024, 20, 32–40, doi:10.3762/bjoc.20.5

• , and graphene nanoplatelets) are achieved through noncovalent encircling with the bent amphiphiles. The resultant imidazole-modified nanocarbons display a pH-responsive surface charge, as evidenced by NMR and zeta-potential measurements. In addition, solubilization of a nitrogen-doped nanocarbon (i.e

• pyridinium-based amphiphiles (Figure 1c). The noncovalent modification of C60 with multiple imidazole side-chains is found to yield a pH-responsive surface charge, as evidenced by NMR and zeta-potential measurements. A nitrogen-doped nanocarbon, i.e., graphitic carbon nitride (g-C3N4), is likewise

• protons upon addition of HCl (40 equiv based on PA-Im; Figure 5a,b). These properties enabled a pH-responsive surface charge of its host–guest composite (Table 2). Accordingly, (PA-Im)n·(C60)m displayed a ZP of 60.3 mV at pH 2.8 contrary to 52.8 mV at pH 6.8 (ΔZP = +7.5 mV) [26]. Control experiments using

pH-Responsive fluorescent supramolecular nanoparticles based on tetraphenylethylene-labelled chitosan and a six-fold carboxylated tribenzotriquinacene

• Nan Yang,
• Yi-Yan Zhu,
• Wei-Xiu Lin,
• Yi-Long Lu and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2023, 19, 635–645, doi:10.3762/bjoc.19.45

• in the presence of TBTQ-C6 was greatly improved. In addition, the fluorescence of CS-TPE was significantly enhanced by introducing TBTQ-C6, and remained relatively stable with variations in pH for both CS-TPE and TBTQ-C6/CS-TPE. Such pH-responsive supramolecular spherical nanoparticles with stable

• stimuli, pH response is of particular interest in the construction of supramolecular systems for intelligent drug delivery because of the presence of pH gradients in the microenvironment of organs, tissues, and cell organelles [5]. In the past years, pH-responsive and other stimuli-responsive

• construct pH-responsive supramolecular vesicles and molecule-scale drug carriers, respectively. Both of them exhibited pH-responsive properties, with the host–guest binding disintegrating when the pH of the solution is adjusted to 5.5 and the binding regenerated when the pH is restored to 7.4. These

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• energy generation [45]. Boyaci and Orakdogen reported pH-responsive cryogels based on the monomer N,N-dimethylaminoethyl methacrylate (DMAEMA), crosslinked with acrylamido-2-methylpropanosulphonic acid (AMPS), where the swelling of the cryogels was heavily dependent on solution pH [46]. pH-Responsive

• cryogels have also been prepared comprising polyamidoamine (PAMAM) dendrimers, whereby the cryogels were stable under acidic conditions, and degrade at physiological solution pH (7.4) [47]. 3.3. Dual temperature and pH-responsive cryogels During cryogel design and production a diverse range of starting

• monomers and/or polymers can be used, selected for desired properties to be exhibited in the final polymer matrix. Therefore, it is possible to combine thermo-responsive and pH-responsive properties through cryogelation techniques, resulting in a cryogel which responds to both changes in environmental

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• pH-responsive nano-assemblies with switchable size and structure are formed by the association of a photoacid, anthocyanidin, and a linear polyelectrolyte in aqueous solution. Specifically, anionic disulfonated naphthol derivatives, neutral hydroxyflavylium, and cationic poly(allylamine) are used as

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• -closed SP state. The peptide 14 has been demonstrated pH responsive reversible red fluorescence staining of acidic lysosomes in A549 cell lines (Figure 11C). Conclusion Schmuck group’s outstanding contributions in peptide-based fluorescent probes research field is summarized in this review. The

Easy access to a carbohydrate-based template for stimuli-responsive surfactants

• Thomas Holmstrøm,
• Daniel Raydan and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2020, 16, 2788–2794, doi:10.3762/bjoc.16.229

• surfactants are triggered, thereby releasing the cargo [8]. Guo and co-workers have earlier succeeded with the use of pH-sensitive surfactants and even introduced the term “flipids” for such pH-responsive lipids [7][8]. This term could also describe compounds where the binding of a guest molecule is able to

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• development of novel drug nanocarrier assemblies. Keywords: aqueous self-assembly; pH-responsive systems; secondary structure; self-assembled nanostructures; solid-phase peptide synthesis; Introduction The self-assembly of small molecules is a ubiquitous phenomenon in nature [1] and also has key

• -responsiveness of self-assembled peptides has been extensively exploited for potential applications, with particular focus on drug delivery systems (DDS) [40], as injectable gels for tissue engineering [41][42], and biosensing applications [43]. pH-responsive DDS can deliver the drug to a specific tissue or

• Information File 1) of galectin-1, a β-sheet lectin protein that is available in bovine spleen [53] (for a detailed crystal structure see the Protein Data Bank; PDB ID 1SLT). Given the amphiphilic and pH-responsive nature of PEP-1, we investigated both the pH- and concentration-dependent formation of

Morphology-tunable and pH-responsive supramolecular self-assemblies based on AB₂-type host–guest-conjugated amphiphilic molecules for controlled drug delivery

• Yang Bai,
• Cai-ping Liu,
• Di Chen,
• Long-hai Zhuo,
• Huai-tian Bu and
• Wei Tian

Beilstein J. Org. Chem. 2019, 15, 1925–1932, doi:10.3762/bjoc.15.188

• utilized as host units to construct these stimuli-responsive supramolecular self-assemblies [21][22][23][24][25][26][27]. For example, β-CD can form inclusion complexes with guests such as azobenzene [28][29], ferrocene [30][31] and benzimidazole [32][33][34] to construct light-, redox-, and pH-responsive

• on pH-responsive supramolecular self-assemblies by utilizing β-CD-benzimidazole2 (β-CD-BM2) as AB2-type amphiphilic HGCMs for the delivery and controlled release of doxorubicin (DOX). β-CD-BM2 was first synthesized by click reaction (Scheme 1a). β-CD-BM2 formed fan-shaped self-assemblies (FSSAs) at

• hydrophobic core and β-CD moieties as outer hydrophilic shell. The basic cell experiments confirmed that the pH-responsive supramolecular self-assemblies based on β-CD-BM2 have a potential application in the field of drug delivery. Results and Discussion Synthesis of the host–guest-conjugated amphiphilic

New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions

• Iveta Chena Tichá,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80

• organoselenium-bridged bis-β-CDs. Subsequently, the same research group [26] investigated the performance of inclusion complexes of native and permethylated β-CDs and cinchona alkaloids as pH-responsive binding systems. Nevertheless, to the best of our knowledge, CD derivatives with covalently bonded cinchona

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

• Antonella Di Vincenzo,
• Antonio Palumbo Piccionello,
• Alberto Spinella,
• Delia Chillura Martino,
• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59

• . The desired responsivity to pH variations of the nanosponges obtained was verified by means of absorption tests on a set of organic pollutant model molecules. Keywords: calixarenes; nanosponges; pH-responsive materials; pollutants; polyaminoazides; Introduction The ability to provide a response to

• presence of unreacted alkyne groups. Sequestration abilities of the CaNS nanosponges The possible pH-responsive sequestration abilities of materials CaNS-I and CaNS-II were verified by means of sequestration tests on a set of suitable guest, namely p-nitroaniline derivatives 6–10 and dyes 11–15 (Figure 4

• work we verified the feasibility of synthesizing new pH-responsive calixarene nanosponges by using two different polyaminoazide mixtures as the reticulating agent. Full characterization (HR-ESIMS, FTIR, 1D and 2D NMR) of the mixtures has been provided. It is particularly important to stress that the

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• conversion of glucose in a tandem reaction [82]. The hydrophilic block of their polymersomes was PEG, and the hydrophobic block contained both poly[2-(diethylamino)ethyl methacrylate] (PDEAEM) which is pH responsive, and poly[4-(3,4-dimethylmaleimido)butyl methacrylate] (PDMIBM) as cross-linker. The activity

Binding abilities of polyaminocyclodextrins: polarimetric investigations and biological assays

• Marco Russo,
• Daniele La Corte,
• Annalisa Pisciotta,
• Serena Riela,
• Rosa Alduina and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2751–2763, doi:10.3762/bjoc.13.271

• ][41]. Moreover, the same products have been used for the synthesis of pH-responsive nanosponges [42]. In view of possible further applications, the present work is aimed at verifying the abilities of AmCD materials synthesized by us to act as bimodal supramolecular ligands. To the best of our

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• CDs. Subsequently in 2014, the same group was able to show that coating of calcium alginate (CA) beads with chitosan hydrogel-based CDs yielded a new nanomaterial that could be employed as a pH-responsive drug-delivery vehicle (Scheme 21) [56]. The CDs were used as a protective layer onto the CA beads

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

• Jie Wang,
• Zhiqiang Qiu,
• Yiming Wang,
• Li Li,
• Xuhong Guo,
• Duc-Truc Pham,
• Stephen F. Lincoln and
• Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

• hydrogel network disassociates. This process is reversible through irradiation at 450 nm. 5.2. pH-Responsive materials In 2007, Yui et al. reported a pH-responsive polymer system in which the simultaneous host–guest complexation by γ-CD of two of the 3.4 kDa average molecular weight poly(ethylene glycol)-b

• conditions, when several α-CD thread onto a single polymer chain to form a polyrotaxane they may aggregate in a localized crystalline state to effectively form cross-links between the polyrotaxanes in a hydrogel network [97][98][99]. A group of pH-responsive hydrogels which comprises four adamantyl

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

• Shawna L. Balof,
• K. Owen Nix,
• Matthew S. Olliff,
• Sarah E. Roessler,
• Arpita Saha,
• Kevin B. Müller,
• Ulrich Behrens,
• Edward J. Valente and
• Hans-Jörg Schanz

Beilstein J. Org. Chem. 2015, 11, 1960–1972, doi:10.3762/bjoc.11.212

• , OR 97203, USA 10.3762/bjoc.11.212 Abstract Three new ruthenium alkylidene complexes (PCy3)Cl2(H2ITap)Ru=CHSPh (9), (DMAP)2Cl2(H2ITap)Ru=CHPh (11) and (DMAP)2Cl2(H2ITap)Ru=CHSPh (12) have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl

• )-4,5-dihydroimidazol-2-ylidene). Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization

• catalysts or systems where the activity can be controlled by external stimuli [38][39][40][41][42][43][44]. In metathesis, pH is a very straightforward stimulus that can fulfill two independent functions for catalysts bearing pH-responsive ligands resulting in metathesis activation [45][46][47][48][49][50

Impact of multivalent charge presentation on peptide–nanoparticle aggregation

• Daniel Schöne,
• Boris Schade,
• Christoph Böttcher and
• Beate Koksch

Beilstein J. Org. Chem. 2015, 11, 792–803, doi:10.3762/bjoc.11.89

• charged gold nanoparticles. The overall primary sequence of VW05 was designed to provide a pH-responsive aggregation of nanoparticles based on electrostatic interactions. Accordingly, a scrambled version of VW05 with the same amino acid composition and net charge did not show any evidence for

Multivalent dendritic polyglycerolamine with arginine and histidine end groups for efficient siRNA transfection

• Fatemeh Sheikhi Mehrabadi,
• Hanxiang Zeng,
• Mark Johnson,
• Cathleen Schlesener,
• Zhibin Guan and
• Rainer Haag

Beilstein J. Org. Chem. 2015, 11, 763–772, doi:10.3762/bjoc.11.86

• ) Arg to His ratio, showed efficient siRNA transfection with minimal cytotoxicity (cell viability ≥ 90%) in NIH 3T3 cells line. We also demonstrated that the cytotoxicity of dPG-NH2 decreased as a result of amino acid functionalization. While the incorporation of both cationic (Arg) and pH-responsive

Synthesis and characterization of pH responsive D-glucosamine based molecular gelators

• Navneet Goyal,
• Hari P. R. Mangunuru,
• Bargav Parikh,
• Sonu Shrestha and
• Guijun Wang

Beilstein J. Org. Chem. 2014, 10, 3111–3121, doi:10.3762/bjoc.10.328

• naproxen from the pH responsive gels were also analyzed under acidic and neutral conditions. Our findings are useful for the design of novel triggered release self-assembling systems and can provide an insight into the influence of the the structure on gelation. Keywords: glucosamine; hydrogelators

• ; naproxen; organogelator; pH responsive; self-assembly; Introduction Low molecular weight gelators (LMWGs) have drawn great attention over the past few decades due to the formation of supramolecular structures and their potential applications as advanced materials [1][2][3][4][5][6][7]. LMWGs are also

• the controlled release of certain biological agents [17][18][19][20][21][22][23][24][25][26][27]. Molecular gelators containing photo or pH responsive functional groups are able to form multi-stimuli responsive gels. These resulting gels may find applications as advanced soft functional materials [28

Preparation and evaluation of cyclodextrin polypseudorotaxane with PEGylated liposome as a sustained release drug carrier

• Kayoko Hayashida,
• Taishi Higashi,
• Daichi Kono,
• Keiichi Motoyama,
• Koki Wada and
• Hidetoshi Arima

Beilstein J. Org. Chem. 2014, 10, 2756–2764, doi:10.3762/bjoc.10.292

• various targeting-ligands such as antibodies, sugars and folic acid to LPs [30][31][32]. Recently, stimulus responsive LPs such as bubble LPs, pH responsive LPs and thermoresponsive LPs have been developed as smart drug carriers [33][34][35]. PEGylated LP (PEG-LP) is one of the most popular LP products

Synthesis and characterization of a hyper-branched water-soluble β-cyclodextrin polymer

• Francesco Trotta,
• Fabrizio Caldera,
• Roberta Cavalli,
• Andrea Mele,
• Carlo Punta,
• Lucio Melone,
• Franca Castiglione,
• Barbara Rossi,
• Monica Ferro,
• Vincenza Crupi,
• Domenico Majolino,
• Valentina Venuti and
• Dominique Scalarone

Beilstein J. Org. Chem. 2014, 10, 2586–2593, doi:10.3762/bjoc.10.271

• mg/mL) over a wide pH range. However, at a pH below 1 the protonation of carboxylic acid groups leads to a precipitate. As predictable, if neutral pH is restored, all the precipitated polymer is solubilized again. This behavior could be of interest in pH responsive drug delivery systems. In addition

A promising cellulose-based polyzwitterion with pH-sensitive charges

• Thomas Elschner and
• Thomas Heinze

Beilstein J. Org. Chem. 2014, 10, 1549–1556, doi:10.3762/bjoc.10.159

• ., acid dissociation constants, isoelectric point and complexation, were investigated by potentiometric titration (pH), nephelometry, rheology and dynamic light-scattering. The formation of pH-responsive interpolyelectrolyte complexes applying polydiallyldimethylammonium chloride was preliminary studied

• of the cellulose derivatives. Acid dissociation constants, isoelectric point and complexation behavior are in good agreement and thus, a well characterized zwitterionic cellulose carbamate with excellent properties was discovered. Preliminary studies show the formation of pH-responsive

Polymeric redox-responsive delivery systems bearing ammonium salts cross-linked via disulfides

• Christian Dollendorf,
• Martin Hetzer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 1652–1662, doi:10.3762/bjoc.9.189

• this regard, poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-dimethylamino)ethyl methacrylate (PDMAEMA) based hydrogels are the most extensively studied representatives. Due to the protonation of covalently attached tertiary amine groups, PDMAEMA exhibits pH-responsive behavior and is used in gene

• delivery [5][6][7]. In general, temperature- and pH-responsive hydrogels containing hydrophilic monomers show low toxicity along with a high efficiency in drug delivery [8]. Besides, cross-linked cationic nanogels have been suggested as DNA delivery systems [9][10][11]. Hamamoto et al. reported a cross

• temperatures before cloud points are reached [42][52]. Since poly(DMAEMA) is not only a temperature-responsive, but also a pH-responsive polymer, the same measurements were conducted in pH 10 buffer solution. To ensure a good comparability the polymer concentration was held constant at 10 mg·mL−1 and the same

The synthesis of well-defined poly(vinylbenzyl chloride)-grafted nanoparticles via RAFT polymerization

• John Moraes,
• Kohji Ohno,
• Guillaume Gody,
• Thomas Maschmeyer and
• Sébastien Perrier

Beilstein J. Org. Chem. 2013, 9, 1226–1234, doi:10.3762/bjoc.9.139

• polymerization (ATRP) [30][31]. It has, therefore, been used in a variety of systems as a precursor to glycopolymer stars [29], photo- and pH-responsive nanoparticles [30], nanofibres [28], comb, graft and star polymers [27], and triblock copolymers [26]. While there have been reports of the (co)polymerization

Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

• Gero Maatz,
• Arkadius Maciollek and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1929–1935, doi:10.3762/bjoc.8.224

• formation of a thermo- and pH-responsive polymer bearing an azo dye at the end group. In a first step, a chain-transfer polymerization (CTP) of N-isopropylacrylamide (1) was carried out in the presence of 3-mercaptopropionic acid (2) and with 4,4’-azobis(4-cyanovaleric acid) as initiator, to achieve a high