CrystEngComm Blog

A new paper by Wang et al. reports the facile synthesis of dispersed polyacrylic acid (PAA)/calcium carbonate nanoparticles which show ultrahigh loading capacity for the liver cancer drug doxorubin (DOX), in addition to its pH sensitive release.

While calcium carbonate particles are attractive potential drug delivery vehicles due to their biocompatibility and pH sensitivity, previously synthesised particles have been micrometer sized and show only limited drug uptake, both of which present barriers to their use.   These issues have now been overcome.  Using PAA-sodium salt as a template, PAA/calcium carbonate particles were produced with an average size of 120 nm by ion exchange followed by heating in carbon dioxide (see diagram below).

The presence of carboxylate groups in PAA is the root of the new nanoparticles’ high uptake of positively charged molecules such as DOX– up to 98 % loading efficiency was observed.  Release of DOX was shown to be faster in mildly acidic conditions like that in extracellular cancer cells, allowing targeting of these cells.

The anti-cancer activity of DOX-loaded PAA/calcium carbonate particles in vitro was compared to DOX-free particles and free DOX using the standard MTT assay.   Cytotoxicity of free DOX was similar to that of the DOX-loaded particles, while the DOX-free particles showed no cytotoxicity.   The performance of free-DOX was also compared to DOX-loaded nanoparticles in vivo.   Compared to the control, the group treated with DOX-loaded nanoparticles showed a 76 % reduction in liver tumour size, while the group treated with free DOX showed a 41 % reduction.   In addition, there were no toxic effects observed for DOX-loaded particles.

These results demonstrate the potential application of PAA/calcium carbonate nanoparticles as delivery vehicles for doxorubin.  Further studies are being carried out to investigate the inclusion of magnetic and/or fluorescent compounds to produce multifunctional materials for simultaneous cancer diagnostic and therapeutic application.

For more information, see the full paper at:

Designed preparation of polyacrylic acid/calcium carbonate nanoparticles with high doxorubicin payload for liver cancer chemotherapy
Hanzhu Shi, Lu Li, Lingyu Zhang, Tingting Wang, Chungang Wang, Dongxia Zhu and Zhongmin Su
CrystEngComm, 2015, Advance Article
DOI: 10.1039/C5CE00708A

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Gwenda Kyd has a PhD in metallocarborane chemistry from the University of Edinburgh. Other research work includes the spectroscopic study of the structure of glasses and organometallic electron-transfer reactions and the preparation of new inorganic phosphors. She has recently published a book on chemicals from plants.

A new paper by Yu-Bin Dong et al reports a metal-organic framework (MOF) which not only reversibly adsorbs two different classes of volatile organic compounds (VOCs), but within each class also shows selectivity allowing separation of chemically similar examples.

VOCs are widely used in the chemical industry but their release into the environment is undesirable, as they can cause damage both to the environment and to human health.  Porous materials such as MOFs are attractive as potential adsorbents of VOCs and could also allow separation of examples with similar boiling points, which proves difficult by other methods such as distillation.

The new MOF consists of ditriazole-N-butylcarbazole ligands bridging Cu ions, forming a framework with square-like pores.  The ligand butyl groups point into the pores, making them hydrophobic.   The adsorption of VOCs classified as chlorocarbons (e.g. CH₂Cl₂) and aromatic solvents such as benzene and toluene were shown to be fully reversible under ambient conditions.

Tests on the selectivity towards chlorocarbons showed that CHCl₃ was adsorbed in preference to CH₂Cl₂ from a mixture.  This suggests that, unusually, selectivity may be based on the polarity of the molecules rather than the size – CHCl₃ is larger but less polar than CH₂Cl₂.

In the case of the aromatic molecules, it proved possible to separate benzene and toluene from mixtures of toluene/ethylbenzene/xylene and ethylbenzene/xylene, respectively.   In both these systems, the larger molecules are adsorbed in preference to the smaller (benzene or toluene, respectively) – see diagram below.

Rather than being determined by the size or polarity of the solvent molecules, this can be explained if the hydrophobic properties are considered.  More hydrophobic molecules, such as ethylbenzene, are preferentially adsorbed into the hydrophobic pores present in the MOF, where they form favourable hydrophobic interactions.

The MOF reported here adds to the range available that show specific properties with regards to adsorption and separation of VOCs, unusually demonstrating specificity related to both the polarities and hydrophobicity of the VOCs.

For more information read the full paper at:

CrystEngComm, 2015, Advance Article
DOI: 10.1039/C5CE00547G

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Gwenda Kyd has a PhD in metallocarborane chemistry from the University of Edinburgh. Other research work includes the spectroscopic study of the structure of glasses and organometallic electron-transfer reactions and the preparation of new inorganic phosphors. She has recently published a book on chemicals from plants.

In a recent paper, Langford et al report the formation of three new molecular porous materials with tunable channels.  Tunability of the size and shape of the channels is important in the design of materials for gas sensing, guest exchange, catalysis and drug delivery.  Other important factors such as thermal and solvent stabilities are also good.

The new compounds are readily prepared from tin(IV) porphyrin phenolates. Their structures feature a one-dimensional hourglass-shaped channel lined with methyl groups.  The nature of the channel is readily varied by changing the methyl substitution of the phenolate component.  In this way, the pore radius can be varied from 3.1 Å to 4.5 Å (see diagram below, showing the three compounds down the crystallographic c axis with channels shown as orange spheres and phenolic methyl groups lining the channel shown in purple).

The compounds are robust compared to other molecular porous materials, thought to be due to a combination of stabilisation by hydrogen bonding and stacking of the aromatic groups.  In combination with the tunability, this suggests potential use for guest exchange or in small molecule capture applications and further investigation of this is ongoing.

For more information see the full paper at:

Supramolecular materials with robust and tunable channels constructed from tin(IV)porphyrin phenolates
Shuang Wang, Craig Forsyth and Steven J. Langford
CrystEngComm, 2015,17, 3060-3063

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Gwenda Kyd has a PhD in metallocarborane chemistry from the University of Edinburgh. Other research work includes the spectroscopic study of the structure of glasses and organometallic electron-transfer reactions and the preparation of new inorganic phosphors. She has recently published a book on chemicals from plants.

Nitrobenzene is an important industrial material used in the production of aniline, dyes, pharmaceuticals and explosives.  However, it is highly toxic, considered likely to be a human carcinogen and does not readily degrade so accurate sensing of nitrobenzene in the environment, even at very low concentrations, is required.

A new paper presents a Cd-based metal-organic framework (MOF) as a highly selective and efficient sensor of nitrobenzene.  The MOF is based on a new flexible ligand with aromatic character, chosen to complement nitrobenzene’s electron withdrawing character.  The ligand, 1,1-(1,4-phenylenebis(methylene))bis(1H-pyrazole-3,5-dicarboxylicacid) and a source of Cd react under hydrothermal conditions to form the new Cd-MOF.

This shows a fluorescence emission when excited at 297 nm which is quenched by the presence of nitrobenzene (see diagram below).

The suggested mechanism of quenching involves photoinduced electron transfer. Quenching is inversely related to the concentration of nitrobenzene and significant quenching occurs at concentrations as low as 50 ppm nitrobenzene. Thus, Cd-MOF is suggested as a sensitive, rapid probe for low concentrations of nitrobenzene.

For the full paper see:

A new Cd(II)-based metal–organic framework for highly sensitive fluorescence sensing of nitrobenzene

Yu-Pei Xia, Yun-Wu Li, Da-Cheng Li, Qing-Xia Yao, Yu-Chang Du and Jian-Min Dou

CrystEngComm, 2015, Advance Article
DOI: 10.1039/C5CE00162E

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Gwenda Kyd has a PhD in metallocarborane chemistry from the University of Edinburgh. Other research work includes the spectroscopic study of the structure of glasses and organometallic electron-transfer reactions and the preparation of new inorganic phosphors. She has recently published a book on chemicals from plants.