Development of a UV-Stabilized Topical Formulation of Nifedipine for the Treatment of Raynaud Phenomenon and Chilblains

Thermally Induced Phenomena in Amorphous Nifedipine: The Correlation Between the Structural Relaxation and Crystal Growth Kinetics

The particle size-dependent processes of structural relaxation and crystal growth in amorphous nifedipine were studied by means of non-isothermal differential scanning calorimetry (DSC) and Raman microscopy. The enthalpy relaxation was described in terms of the Tool-Narayanaswamy-Moynihan model, with the relaxation motions exhibiting the activation energy of 279 kJ·mol-1 for the temperature shift, but with a significantly higher value of ~500 kJ·mol-1 being obtained for the rapid transition from the glassy to the undercooled liquid state (the latter is in agreement with the activation energy of the viscous flow). This may suggest different types of relaxation kinetics manifesting during slow and rapid heating, with only a certain portion of the relaxation motions occurring that are dependent on the parameters of a given temperature range and time frame. The DSC-recorded crystallization was found to be complex, consisting of four sub-processes: primary crystal growth of αp and βp polymorphs, enantiotropic βp → βp' transformation, and βp/βp' → αp recrystallization. Overall, nifedipine was found to be prone to the rapid glass-crystal growth that occurs below the glass transition temperature; a tendency of low-temperature degradation of the amorphous phase markedly increased with decreasing particle size (the main reason being the increased number of surface and bulk micro-cracks and mechanically induced defects). The activation energies of the DSC-monitored crystallization processes varied in the 100-125 kJ·mol-1 range, which is in agreement with the microscopically measured activation energies of crystal growth. Considering the potential correlations between the structural relaxation and crystal growth processes interpreted within the Transition Zone Theory, a certain threshold in the complexity and magnitude of the cooperating regions (as determined from the structural relaxation) may exist, which can lead to a slow-down of the crystal growth if exceeded.

Temperature-responsive hydrogel-grafted vessel-on-a-chip: Exploring cold-induced endothelial injury

Cold-induced vasoconstriction is a significant contributor that leads to chilblains and hypothermia in humans. However, current animal models have limitations in replicating cold-induced acral injury due to their low sensitivity to cold. Moreover, existing in vitro vascular chips composed of endothelial cells and perfusion systems lack temperature responsiveness, failing to simulate the vasoconstriction observed under cold stress. This study presents a novel approach where a microfluidic bioreactor of vessel-on-a-chip was developed by grafting the inner microchannel surface of polydimethylsiloxane with a thermosensitive hydrogel skin composed of N-isopropyl acrylamide and gelatin methacrylamide. With a lower critical solution temperature set at 30°C, the gel layer exhibited swelling at low temperatures, reducing the flow rate inside the channel by 10% when the temperature dropped from 37°C to 4°C. This well mimicked the blood stasis observed in capillary vessels in vivo. The vessel-on-a-chip was further constructed by culturing endothelial cells on the surface of the thermosensitive hydrogel layer, and a perfused medium was introduced to the cells to provide a physiological shear stress. Notably, cold stimulation of the vessel-on-a-chip led to cell necrosis, mitochondrial membrane potential (ΔΨm) collapse, cytoskeleton disaggregation, and increased levels of reactive oxygen species. In contrast, the static culture of endothelial cells showed limited response to cold exposure. By faithfully replicating cold-induced endothelial injury, this groundbreaking thermosensitive vessel-on-a-chip technology offers promising advancements in the study of cold-induced cardiovascular diseases, including pathogenesis and therapeutic drug screening.

Complex Spectroscopy Studies of Nifedipine Photodegradation

The aim of this work is to highlight the influence of UV light on the hydrolysis reaction of nifedipine (NIF) in the presence of alkaline solutions. In this context, the photodegradation of NIF in the absence of alkaline solutions caused (a) a change in the ratio between the absorbances of three bands in the UV-VIS spectra localized at 224-240 nm, 272-276 nm and 310-340 nm, assigned to the electronic transitions of -COOCH3 groups, -NO2 groups and a heterocycle with six atoms; (b) a red-shift of the photoluminescence (PL) band from 458 nm to 477 nm, simultaneous with an increase in its intensity; (c) a decrease in the ratio of the Raman line intensities, which peaked at 1224 cm-1 and 1649 cm-1, associated with the vibrational modes of -C-C-O in the ester group and C=C stretching; and (d) a decrease in the ratio between the absorbances of the IR bands, which peaked at 1493 cm-1 and 1223 cm-1, associated with the vibrational modes of the -NO2 group and C-N stretching. These changes were explained considering the NIF photodegradation reaction, which leads to the generation of the compound 4-(2-nitrosophenyl)-2.6-dimethyl-3.5-dimethoxy carbonyl pyridine. The interaction of NIF with NaOH in the absence of UV light was demonstrated to induce changes in the vibrational mode of the -C-C-O bond in the ester group. The photodegradation of NIF after its reaction with NaOH induces significant changes highlighted in its (a) UV-VIS spectra, by the shift of the absorption band at 238 nm; (b) PL spectra, by the supraunitary value of the ratio between the emission band intensities at 394-396 nm and 450 nm; (c) Raman spectra, by the change in the ratio between the intensities of the lines that peaked at 1224 cm-1 and 1649 cm-1 from 0.61 to 0.49; and (d) FTIR spectra, by the lowered absorbance of the IR band at 1493 cm-1 assigned to the vibrational mode of the -NO2 group as a result of the generation of the nitroso compound. These changes were explained considering the hydrolysis reaction products of NIF, as the nitroso compound is converted to a lactam-type compound. The photodegradation reaction rate constants of NIF and NIF after interaction with NaOH were also reported. The decrease in thermal stability of NIF samples after interaction with NaOH, as well as of NIF after exposure to UV light compared to NIF prior to exposure to UV light, was demonstrated by thermogravimetry, and the key fragments were confirmed by mass spectrometry.

Cold Hands or Feet: Is It Raynaud's or Not?

Raynaud's phenomenon is an exaggerated response to cold stimuli that may be primary or secondary. The diagnosis relies on patient history and physical examination to distinguish RP from other vasomotor dysfunction (e.g. acrocyanosis, pernio, small fiber neuropathy with vasomotor symptoms, and complex regional pain syndrome). Achenbach syndrome, or spontaneous venous hemorrhage, may also be mistaken for RP but is a self-limiting phenomenon. Laboratory evaluation and vascular diagnostic testing may identify SRP causes. Regardless of etiology, treatment includes warming with trigger avoidance, and consideration of vasodilators (eg. calcium channel, alpha-1 blockers). SRP with digital ulceration may require PDE5i, endothelin-1 receptor blockers, and prostanoids. Refractory cases may require pneumatic arterial pumps, botulinum toxin administration, or surgical sympathectomy.

Fluorinated dihydropyridines as candidates to block L-type voltage-dependent calcium channels

Voltage-gated calcium (Ca_v) channels malfunction may lead to Alzheimer's and cardiovascular disorders, thus a critical protein target for drug development and treatment against several diseases. Indeed, dihydropyridines (DHPs) as nifedipine and amlodipine are top-selling pharmaceuticals and, respectively, the 121st and 5th most prescribed drugs in the United States that have been used as successful selective blockers for L-type Ca2+ channels (LCC) and may be helpful model structures to compare with new DHP analogs. In this context, we have performed a structure-based drug design (SBDD) study of several fluorinated DHPs by using homology modeling, molecular docking, quantitative structure activity relationship (QSAR) and molecular dynamics calculations. Such approaches combined with molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) interaction energy results and screening of ADMET (absorption, distribution, metabolism, excretion and toxicity) properties indicate that all ligands in this study are potential new candidates to be tested experimentally for inhibition of LCC and may have higher affinities than the commonly used drugs, being convenient synthetic routes proposed for 11-16, which are among the ligands that showed the best theoretical results concerning LCC inhibition. Furthermore, the ligand interactions with the binding site were carefully examined using the topological noncovalent interactions (NCI) method, which highlighted specifically responsible amino acid residues that increase the spontaneity of the new proposed DHP ligands.Communicated by Ramaswamy H. Sarma.

Melissa officinalis: Composition, Pharmacological Effects and Derived Release Systems-A Review

Melissa officinalis is a medicinal plant rich in biologically active compounds which is used worldwide for its therapeutic effects. Chemical studies on its composition have shown that it contains mainly flavonoids, terpenoids, phenolic acids, tannins, and essential oil. The main active constituents of Melissa officinalis are volatile compounds (geranial, neral, citronellal and geraniol), triterpenes (ursolic acid and oleanolic acid), phenolic acids (rosmarinic acid, caffeic acid and chlorogenic acid), and flavonoids (quercetin, rhamnocitrin, and luteolin). According to the biological studies, the essential oil and extracts of Melissa officinalis have active compounds that determine many pharmacological effects with potential medical uses. A new field of research has led to the development of controlled release systems with active substances from plants. Therefore, the essential oil or extract of Melissa officinalis has become a major target to be incorporated into various controlled release systems which allow a sustained delivery.

Raynaud's phenomenon and digital ulcers: advances in evaluation and management

PURPOSE OF REVIEW

The aim of this review is to give an update on advances in evaluation and management of systemic sclerosis (SSc)-related Raynaud's phenomenon and digital ulceration, focusing on reports from the last 18 months. The increasing recognition of the huge impact of Raynaud's phenomenon and of digital ulceration on the everyday lives of patients with SSc has sparked enthusiasm internationally to develop better outcome measures and better treatments, and so a review is timely.

RECENT FINDINGS

There have been recent advances in the development of patient reported outcome instruments [e.g. the Hand Disability in Systemic Sclerosis-Digital Ulcers (HDISS-DU) instrument] and also in noninvasive imaging techniques, including thermography and laser Doppler methods. Improved outcome measures will facilitate future clinical trials, both early phase proof-of-concept and later phase trials. New insights have been gained into mechanisms of action and methods of administration of 'conventional' therapies, for example phosphodiesterase inhibitors and intravenous prostanoids. New treatment approaches are being investigated, including topical and procedural therapies.

SUMMARY

Clinicians can look forward to seeing these advances translating into clinical benefit over the next 5 years. To help ensure this, they should strive whenever possible to recruit patients with SSc-related digital vasculopathy into observational studies and clinical trials.

Raynaud's phenomenon

Raynaud's phenomenon (RP) is a common vasospastic condition which affects ~5% of the general population. The majority of individuals have primary RP; however, Raynaud's can also occur secondary to a broad range of underlying medical conditions and drug therapies. RP is a cardinal feature in patients with systemic sclerosis and is often the earliest symptom of the disease. Unlike primary RP, patients with secondary RP can develop persistent digital ischaemia, including ulcers and gangrene. Patients require a comprehensive clinical assessment and investigation, in particular, the detection of autoantibodies and nailfold capillaroscopic abnormalities. Non-pharmacological management is indicated in all patients. There are a wide range of available drug therapies to treat RP, including when complicated by digital ulceration, and surgical intervention is sometimes required. Future research is needed to understand the complex pathogenesis of RP and to measure the impact and severity of RP to develop optimised approaches to management.

Use of calcium channel blockers in dermatology: a narrative review

Introduction: Calcium channel blockers (CCB) are commonly used for cardiovascular diseases. The evidence supporting the use of CCB in dermatology is mostly anecdotal and limited to case reports or small case series.Areas covered: This review article is divided into two parts. The first part discusses the therapeutic use of CCB in dermatology. The second part focuses on mucocutaneous adverse reactions due to the administration of CCB.Expert opinion: The use of CCB in dermatology is mainly based on its properties as a vasodilator and the inhibition of muscle contractions, such as pernio, anal fissures, facial wrinkles, and painful leiomyoma. However, there remain other modes of action to explain its clinical use in calcinosis, keloid, pressure ulcer, and fibromatosis. Compared to oral CCB, the lack of systemic side effects would make topical use of CCB an attractive alternative in the treatment of skin diseases, but the evidence for topical CCB is still limited, and there is a lack of standardized topical formulation. The main mucocutaneous adverse effects of CCB include gingival hyperplasia, phototoxicity, eczema, psoriasis and risk of skin cancers. Plausible factors for these adverse events include CCB's photoinstability, aldosterone synthesis inhibition, disturbed calcium homeostasis and immunosuppressive properties.

Dissolution of amorphous nifedipine from micelle-forming carboxymethylcellulose derivatives

We show that a novel amphiphilic graft copolymer combining the biodegradability and biocompatibility of oxidized carboxymethylcellulose (CMC) with that of hydrophilic poly(ethylene glycol) (PEG), and hydrophobic dodecylamine (DDA), improves the solubility and dissolution performance of nifedipine (NIF), considered as a model hydrophobic drug. The hydrophobic components of the graft copolymer have the multiple effect of favouring micelle formation and loading. At the same time, the interaction between the hydrophobic core and NIF has the secondary effect to suppress drug crystallization, favouring its dissolution, and to increase photostability. Oxidized CMC-g-PEG-DDA micelles reached values of drug concentration, loading capacity and encapsulation efficiency as high as 340 μg mL^-1, 6.4 % and 34.1 %, respectively. Loaded micelles showed a good stability with a limited release profile at pH 1.2, whereas at pH 7.4 the swollen cores enable much higher and progressive release, that reaches 3.4 and 6.6 % after 3 and 5 h, respectively, corresponding to very competitive concentration of 34 and 66 μg mL^-1.