Separation and determination of chiral composition in penicillamine tablets by capillary electrophoresis in a broad pH range

DNA-Immobilized Special Conformation Recognition of L-Penicillamine Using a Chiral Molecular Imprinting Technique

A new chiral molecularly imprinted polymer (MIP) sensor with dual recognition ability was developed for the highly selective separation of enantiomers with toxic side effects in drugs. The sensor contains double-stranded deoxyribonucleic acid (dsDNA) as the element that immobilizes the chiral molecular conformation: the dsDNA enables the imprinted cavities to match the three-dimensional structure and functional groups from the chiral molecule. By embedding the spatial orientation of dsDNA in MIPs, one can accurately capture and immobilize the molecular conformation, eliminating the influence of interfering analogues. Herein, L-penicillamine (L-Pen) was selected as the chiral template molecule and embedded into dsDNA to form dsDNA-L-Pen complex, which was then embedded into the MIPs by electropolymerization. After elution, the stereo-selective imprinted cavities were obtained. The ATATATATATAT-TATATATATATA base sequence showed a high affinity for the embedded L-Pen, which endowed the imprinted cavities with a larger number of sites and improved the selectivity toward Pen enantiomers. Under the optimal working conditions, the current response of the MIP/dsDNA sensor exhibited a positive linear relationship with the logarithm of the L-Pen concentration in the range of 3.0 × 10^-16 to 3.0 × 10^-13 mol/L, and the detection limit was 2.48 × 10^-16 mol/L. After the introduction of dsDNA into the MIP, the selectivity of the sensor toward D-Pen increased by 6.4 times, and the sensor was successfully applied in the analysis of L-Pen in penicillamine tablets.

Nanomaterials-enriched sensors for detection of chiral pharmaceuticals

Advancements in nanoscience and nanotechnology have opened new pathways to fabricate novel nanostructures with interesting properties that would be used for different applications. In this respect, nanostructures comprising chirality are one of the most rapidly developing research fields encompassing chemistry, physics and biology. Chirality, also known as mirror asymmetry, describes the geometrical property of an object that is not superimposable on its mirror image. This characteristic plays a crucial role because these identical forms of chiral species in pharmaceuticals or food additives may exhibit different effects on living organisms. Therefore, chiral analysis is an important field of modern chemical analysis in health-related industries that are reliant on the production of enantiomeric compounds involving pharmaceuticals. This review covers the recent advances dealing with the synthesis, design and advantageous analytical performance of nanomaterials-enriched sensors used for chiral pharmaceuticals. We conclude this review with the challenges existing in this research field and our perspectives on some potential strategies with cutting-edge approaches for the rational design of sensors for chiral pharmaceuticals. We expect this comprehensive review will inspire future studies in nanomaterials-enriched chiral sensors.

Distinction of chiral penicillamine using metal-ion coupled cyclodextrin complex as chiral selector by trapped ion mobility-mass spectrometry and a structure investigation of the complexes

Penicillamine (Pen) is a common chiral drug that is obtained from penicillin. Between the two enantiomers of Pen, only D-Pen can be used to treat cystinuria and rheumatoid arthritis while L-Pen is toxic. Therefore, it requires great efforts for the research of the rigorous analysis and distinction of the two enantiomers. The non-covalent combination of chiral molecules and chiral selectors (CSs) has been proved as a unique strategy for chiral distinction by ion mobility spectrometry in coupling with -mss spectrometry (IM-MS). Here, we developed a simple method to distinguish D, L-Pen by using special CSs for IM-MS separation. The CSs utilized here include cyclodextrins (CD) and linear chain oligosaccharides plus metal ions. We found that non-covalent complexes [Pen+β-CD + Li]⁺ could be easily formed by electrospray ionization of the mixture of the solution, and the chirality of Pen could be effectively recognized by measuring their mobilities due to the different collision cross collision sections of [D-Pen+β-CD + Li]⁺ and [L-Pen+β-CD + Li]⁺. A detailed analysis of [Pen+β-CD + Li]⁺ was then conducted by the optical rotation measurements and NMR experiments to reveal their structural differences. Furthermore, DFT calculation showed the differences of molecular conformation between the complexes. The results provide a new powerful method for fast analysis and recognition of chirality of Pen compounds by IM-MS.

Chirality Transfer from Sub-Nanometer Biochemical Molecules to Sub-Micrometer Plasmonic Metastructures: Physiochemical Mechanisms, Biosensing, and Bioimaging Opportunities

Determining the structural chirality of biomolecules is of vital importance in bioscience and biomedicine. Conventional methods for characterizing molecular chirality, e.g., circular dichroism (CD) spectroscopy, require high-concentration specimens due to the weak electronic CD signals of biomolecules such as amino acids. Artificially designed chiral plasmonic metastructures exhibit strong intrinsic chirality. However, the significant size mismatch between metastructures and biomolecules makes the former unsuitable for chirality-recognition-based molecular discrimination. Fortunately, constructing metallic architectures through molecular self-assembly allows chirality transfer from sub-nanometer biomolecules to sub-micrometer, intrinsically achiral plasmonic metastructures by means of either near-field interaction or chirality inheritance, resulting in hybrid systems with CD signals orders of magnitude larger than that of pristine biomolecules. This exotic property provides a new means to determine molecular chirality at extremely low concentrations (ideally at the single-molecule level). Herein, three strategies of chirality transfer from sub-nanometer biomolecules to sub-micrometer metallic metastructures are analyzed. The physiochemical mechanisms responsible for chirality transfer are elaborated and new fascinating opportunities for employing plasmonic metastructures in chirality-based biosensing and bioimaging are outlined.

Enantiomeric Determination of Drugs in Pharmaceutical Formulations and Biological Samples by Electrokinetic Chromatography

Chirality is a relevant issue in the pharmaceutical field due to the different biological activity that enantiomers of a chiral drug can show. In fact, the desired biological or pharmaceutical activity might be present in only one of the enantiomers, while the other enantiomer(s) may have different biological activity, be inactive or even toxic. This has motivated in recent years the development of drugs marketed as pure enantiomers to avoid exposing the organism to the action of enantiomers that may not be active or even harmful to health. Thus, it is of high interest to develop enantioselective analytical methodologies to control the presence of enantiomeric impurities and to understand the enantioselective metabolism of chiral drugs. This review gives an overview about the analytical strategies developed by electrokinetic chromatography (EKC) from 2010 to June 2019 for the enantiomeric determination of drugs in both pharmaceutical formulations and biological samples. The types of chiral selectors used, the migration order of enantiomers, their resolution, the detection technique employed and the sensitivity achieved are revised and compared. Also, applications to assess the enantiomeric purity control of pharmaceutical formulations and to determine chiral drugs in biological samples to study their metabolism are included. Advantages and limitations of the chiral methods developed by EKC are also discussed.

Nanoparticle-based Chemiluminescence for Chiral Discrimination of Thiol-Containing Amino Acids

The ability to recognize the molecular chirality of enantiomers is extremely important owing to their critical role in drug development and biochemistry. Convenient discrimination of enantiomers has remained a challenge due to lack of unsophisticated methods. In this work, we have reported a simple strategy for chiral recognition of thiol-containing amino acids including penicillamine (PA), and cysteine (Cys). We have successfully designed a nanoparticle-based chemiluminescence (CL) system based on the reaction between cadmium telluride quantum dots (CdTe QDs) and the enantiomers. The different interactions of CdTe QDs with PA enantiomers or Cys enantiomers led to different CL intensities, resulting in the chiral recognition of these enantiomers. The developed method showed the ability for determination of enantiomeric excess of PA and Cys. It has also obtained an enantioselective concentration range from 1.15 to 9.2 mM for PA. To demonstrate the potential application of this method, the designed platform was applied for the quantification of PA in urine and tablet samples. For the first time, we presented a novel practical application of nanoparticle-based CL system for chiral discrimination.

A water-stable homochiral luminescent MOF constructed from an achiral acylamide-containing dicarboxylate ligand for enantioselective sensing of penicillamine

A water-stable homochiral luminescent MOF was obtained by spontaneous symmetry-breaking crystallization from achiral precursors; it exhibits enantioselective sensing of d/l-Pen.

Circular dichroism sensor based on cadmium sulfide quantum dots for chiral identification and detection of penicillamine

A new chemical sensor based on the measuring of circular dichroism signal (CD) was fabricated from cysteamine capped cadmium sulfide quantum dots (Cys-CdS QDs). The chiral-thiol molecules, d-penicillamine (DPA) and l-penicillamine (LPA), were used to evaluate potentials of this sensor. Basically, DPA and LPA provide very low CD signals. However, the CD signals of DPA and LPA can be enhanced in the presence of Cys-CdS QDs. The CD spectra of DPA and LPA exhibited a mirror image profile. Parameters affecting the determination of DPA and LPA were thoroughly investigated in details. Under the optimized condition, the CD signals of DPA and LPA displayed a linear relationship with the concentrations of both enantiomers, ranging from 1 to 35 μM. Detection limits of this sensor were 0.49 and 0.74 μM for DPA and LPA, respectively. To demonstrate a potential application of this sensor, the proposed sensor was used to determine DPA and LPA in real urine samples. It was confirmed that the proposed detection technique was reliable and could be utilized in a broad range of applications.

Recent advances in capillary electrophoretic migration techniques for pharmaceutical analysis

Since the introduction about 30 years ago, CE techniques have gained a significant impact in pharmaceutical analysis. The present review covers recent advances and applications of CE for the analysis of pharmaceuticals. Both small molecules and biomolecules such as proteins are considered. The applications range from the determination of drug-related substances to the analysis of counterions and the determination of physicochemical parameters. Furthermore, general considerations of CE methods in pharmaceutical analysis are described.