Complex Molecular and Biomolecular Systems

Crystal structure determination of bioactive compounds by NMR crystallography

Working group: Claudiu Filip, Gheorghe Borodi,  Xenia Filip, Maria Miclăuș, Ioana Grosu

The growing field of NMR crystallography have led to significant improvements in the methodology for structural characterization of organic solids, primarily from microcrystalline powders, by combined solid-state Nuclear Magnetic Resonance (ss-NMR), powder X-Ray diffraction (PXRD) and molecular modelling in full crystal. Our group has a long standing expertise in this field^[1] and has brought important contributions to both, its methodolgical development and practical applications. The focus was mainly on solving complex structural problems on bioactive compounds, with more than 15 novel crystal structures being reported over the last years for various solid forms of Quecetin, Lisinopril, Acciclovir, Ketoconazole, Tadalafil and Prometazin. Among these, there are two particular cases which deserve special emphasis: (i) Lisinopril dihydrate – a pharmaceutical compound with 24 degrees of freedom to be refined, of which crystal structure was determined^[2] from powder at a level of accuracy very close to that of single crystal X-Ray diffraction, and (ii) anhydrous Quercetin – a natural bioactive compound with multiple hydroxyl groups, for which NMR crystallography has proven indispensable to correctly identify the hydrogen bonding network^[3] which leads to the observed crystal packing pattern.

[1] http://cache2.itim-cj.ro/ttc/
[2] M. Miclăuș, I. Grosu, X. Filip, C. Tripon, C. Filip CrystEngComm 16 (2014) 299-303
[3] X. Filip, I. Grosu, M. Miclăuș, C. Filip  CrystEngComm 15 (2013) 4131-4142

Characterization of the intermolecular interactions between bioligands and macromolecules

Working grup: Adrian Pîrnău, Călin Gabriel Floare, Mihaela Mic, Carmen Bugeac, Mircea Bogdan

Our current research interests are directed towards understanding the mechanisms of interaction between bioligands and macromolecules (plasma proteins, cyclodextrins) in the liquid state, which allow the characterization of molecular systems in its dynamic evolution, using spectrometric (NMR, UV-Vis, Fluorescence) and calorimetric (ITC) techniques, as well as ab initio calculations and molecular dynamics  simulations.

The study of the interaction between drugs and proteins is an important issue from a biochemical and clinical point of view. Transport of drugs in the body, take place via the circulatory system. The plasmatic proteins have the ability to bind and transport a diverse range of drugs, metabolites and organic compounds.

Using the techniques mentioned previously, we determined the stoichiometry and the association constant between zidovudine (AZT) and human serum albumin (HSA), the key parameters specifying the drug affinity to protein^[1].  Cyclodextrins are also used as drug transporters in order to optimize the controlled release of the drugs. Thus the inclusion complex of β-cyclodextrin (β-CD) with 1-Methyl-1-({2-[4-(trifluoromethyl)phenyl]-1,3-thiazol-4-yl}methyl piperidinium chloride (1MPTMPC) has been characterized in solution as well as in solid state^[2].

[1] A. Pîrnău, M. Mic, S. Neamţu, C. G. Floare, M. Bogdan, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 191 (2018) 226–232
[2] M. Mic, A. Pîrnău, C. G. Floare, M. Miclăuș, I. Kacso, M.Palage, M. Bogdan, Journal of Inclusion Phenomena and Macrocyclic Chemistry 92 (2018) 195–204

Screening for new solid forms of bioactive compound by high-throughput crystallization

Working grup: Flavia Martin, Irina Kacsó, Maria Miclăuș, Ioana Grosu

Drugs or dietary supplements development is a complex, expensive and long-term process, within which the optimization of the solid form of the active ingredient represents an important step. The selected solid form directly influences essential properties of a bioactive compound: solubility, stability and bioavailability. Thus, new solid forms screening (polymorphs, salts, co-crystals, hydrates/solvates) is an important process in the development of the final product. New solid forms screening, using high-throughput crystallization techniques, offers the possibility of using a varied range of crystallization methods, ensuring the necessary experimental diversity. Thus, the probability of obtaining stable solid forms is enhanced.

The research group’s expertise led to the preparation and characterization of more than 30 new solid forms, among these some with enhanced stability and solubility. Such an example is Ketoconazole: due to a crystal engineering study, performed with the aim to increase its’ solubility, spectacular results were obtained for a series of binary crystalline systems with di-carboxylic acids. The salt of Ketoconazole with oxalic acid and the co-crystal with fumaric acid present a solubility of 50 and 100 respectively times higher than Ketoconazole^[1].

[1] Flavia A.Martin, Mihaela M. Pop, Gheorghe Borodi, Xenia Filip, Irina Kacsó, Cryst. Growth Des. 13(2013) 4295–4304

Solid-state NMR characterization of polydopamine on isotopically labelled systems

Claudiu Filip in collaboration with Monica Cîrcu from the research team Multifunctional materials and biologically active compounds

Despite the large number of applications reported for polydopamine (PDA), limitations posed by its complex structure makes it difficult for the definite structure elucidation using standard analytical techniques.

To overcome these inherent limitations, a new approach based on solid-state NMR study on PDA samples obtained under different selective isotopic labeling schemes, was introduced. We started this program with the ss-NMR analysis of polydopamine prepared from D₃-ring dopamine (D₃-DA) vs authentic dopamine in D₂O vs H₂O: the results obtained so far provide important new structural and dynamical information on PDA^[1]. In particular, our study proves without any doubt that more than half of the phenyl ring positions remain protonated in PDA and the majority of phenyl / indole rings are rigid. Furthermore, it is evidenced that water molecules undergo a slow diffusion motion inside the sample, as well as in and out the sample.

^[1] M. Cîrcu, C. Filip, Polym. Chem. 9 (2018) 3379-3387

Senzori electrochimici biomimetici

Diana Bogdan, Maria Suciu, Lucian Barbu-Tudoran
Colaborare cu grupul Prof. Cecilia Cristea, Universitatea de Medicină și Farmacie Iuliu Hațieganu din Cluj-Napoca

Senzorii electrochimici au înregistrat o creștere extraordinară în ultimul deceniu datorită progreselor în chimia materialelor și a celor din tehnologiile de comunicație digitală. În particular, electrozii modificați chimic au aplicații practice biomedicale în dezvoltarea unor dispozitive de analiză rapide, sensibile, selective, ușor de utilizat și noninvazive.

Colaborarea cu grupul Prof. Cecilia Cristea (UMF Cluj-Napoca), grup în care se dezvoltă astfel de senzori, a vizat în principal caracterizarea prin microscopie de forță atomică (AFM) și microscopie electronică (SEM/TEM) a trei categorii de senzori electrochimici dezvoltați la UMF Cluj: senzori electrochimici pentru detecția dopaminei^[1], senzori electrochimici pe bază de nanoparticule de polipirol (PPyNPs) decorate cu nanoparticule de aur (AuNPs) pentru detecția selectivă și senzitivă a serotoninei din probe reale de ser^[2] și aptasenzori impedimetrici pentru detecția selectivă a Interleukinei 6 (IL-6) cu utilitate în screeningul cancerului colorectal^[3]. Rezultatele furnizate de grupul nostru au contribuit la caracterizarea morfologică și topografică a suprafaței nanostructurate a electrozilor după fiecare dintre etapele de fabricație.

[1] M Tertiș, A Florea, A Adumitrăchioaie, A Cernat, D Bogdan, L Barbu-Tudoran, N Jaffrezic Renault, R Săndulescu, C Cristea ChemPlusChem 82(4) (2017) 561-569
[2] M Tertiș, PI Leva, D Bogdan, M Suciu, F Graur, C Cristea Biosens Bioelectron 137 (2019) 123-132
[3] M Tertiș, A Cernat, D Lacatiș, A Florea, D Bogdan, M Suciu, R Săndulescu, C Cristea Electrochem Commun 75 (2017) 43-47

Solid-state NMR investigations of polymers

Claudiu Filip, Xenia Filip
Collaboration with: Prof. Jürgen Liebscher, Dr. Alexandrina Nan and Dr. Anca Petran from the research team Multifunctional materials and biologically active compounds

The research undertaken by the Multifunctional materials and biologically active compounds team in the field of polymeric materials and polymer composites address, among others, the development of new polymers / co-polymers, preferably biocompatible / biodegradable, with properties tailored for applications in the pharmaceutical industry, depolution and medicine. To comply with the demands specific to these type of practical applications, a detailed structural characterization, as well as the physico-chemical properties knowledge, of these new systems is absolutly neccessary.

In this context, our research team offers its expertise in ss-NMR structural characterization of polymeric materials, bringing important contributions along the time to a series of remarkable results of this research group on polymers, among which we mention: determination of important structural features of polydopamine^[1], ss-NMR characterization of some polydopamine analogues^[2], and of some new biocompatible / biodegradable polymers based on tartaric acid^[3] and bezofuran-co- arylacetic acid^[4].

[1] J. Liebscher, R. Mrowczynski, S.A. Scheidt, C. Filip, N.D. Hădade, R. Turcu, A. Bende, S. Beck, Langmuir, 29 (2013) 10539-10548
[2]A. Petran, N. D. Hădade, C. Filip, X. Filip, A. Bende, A. Popa, J. Liebscher, Macromolec. Chem. Phys. 219 (2018) 1700564; A. Petran, R. Mrowczynski, C. Filip, R. Turcu, J. Liebscher, Polym. Chem. 6 (2015) 2139-2149
[3]A.Nan, X. Filip, M. Dan, O. Marincaş, J. Cleaner Prod. 210 (2019) 687-696
[4] A. Nan, A. Bunge, M. Cîrcu, A. Petran, N.D. Hădade, X. Filip, Polym. Chem. 8, (2017) 3504-3514

Thermal and mass transport phenomena through mesoporous materials

Collaboration with Laboratory of Molecular Dynamics and Structure of Materials (UDSMM) University of the Littoral Opal Coast, Dunkerque, France.

Among the storage systems, the solid-state systems provide an attractive option for compact gas storage. In last years, we focused on thermal characterization of metal-organic frameworks (MOFs) in compressed pellets to increase their hydrogen adsorption capacity and adsorption/desorption kinetic.

Thermal conductivity of the adsorbent controls the rate at which it can be cooled or heated: an increased thermal conductivity accelerates the hydrogen adsorption/desorption rate.

Estimation of effective thermal conductivity of highly porous materials is often complicated, due to the low heat transfer and poor thermal contact between the sensor and the sample. In this regard, it is worth mention the common contributions of the two groups to both characterisation techniques and optimization of materials properties, with the aim of elucidating the thermal/mass transfer mechanisms through different types of MOFs.

Roumanian contribution: thermal characterization of porous materials by calorimetric techniques and infrared lock-in thermography (LiT), materials elaboration/optimization and their structural/kinetic studies¹.
French contribution: thermal characterization of porous materials by non-contact photothermal radiometry technique (PTR). The results of two groups were correlated, analyzed and disseminated in common publications^2,3.

Brief description of the french research group

The transport phenomena group (part of UDSMM) deals specifically with the transport of heat and mass in different physical (and chemical) processes related to advanced materials. Different thermal characterization techniques adapted to a wide range of materials have been developed in recent years within this group: the photopyroelectrique technique in the cryogenic temperature range (below 100K), the adiabatic scanning calorimetry technique (ASC) for heat capacity measurement and enthalpy changes, and the thermo-reflectance technique for thermal characterization of thin layers.

¹Blăniță G, Streza M, Lazăr MD, Lupu D, Int. J Hydrogen Energ 42 (5), (2017).
²M. Streza, S. Longuemart, E. Guilmeau, M. Depriester, A.H. Sahraoui, Journal of Physics D-Appl. Physics 49 (28) (2016).
³M. Streza, O. Grad, D. Lazăr, M. Depriester, S. Longuemart, A.H. Sahraoui, G. Blăniță, D. Lupu Int. J. Heat Mass Transfer (2019) – under review