Christo Tzachev

Prof. Dr. Christo Tzachev


Research Focus & Metrics

Academic Career Length

3Years (2024-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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6 April 2024 in Molecules
Verified
Journal Article
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TSTsveta Sarafska
Tsveta Sarafska
SIStanislava Ivanova
Stanislava Ivanova
Todor DoudevTodor Doudev
Todor Doudev
CTChristo Tzachev
Christo Tzachev
VPVesselin Petrov
Vesselin Petrov
Tony SpassovTony Spassov
Tony Spassov
The ability of β-CD to form inclusion complexes with ibuprofen (IBU) and at the same time to make a two-phase system with citric acid was explored in the present study for achieving improved solubility and dissolution rate of IBU. Mechanical milling as well as mechanical milling combined with thermal annealing of the powder mixtures were applied as synthetic methods. Solubility and dissolution kinetics of the complexes were studied in compliance with European Pharmacopoeia (ICH Q4B). β-CD and citric acid (CA) molecules were shown to interact by both ball milling (BM), thermal annealing, as well as BM with subsequent annealing. Complexes were also formed by milling the three compounds (β-CD, CA and IBU) simultaneously, as well as by a consecutive first including IBU into β-CD and then binding the formed β-CD/IBU inclusion complex with CA. As a result, ternary β-CD/IBU/CA complex formed by initial incorporation of ibuprofen into β-CD, followed by successive formation of a two-phase mixture with CA, exhibited notably improved dissolution kinetics compared to the pure ibuprofen and slightly better compared to the binary β-CD/IBU system. Although the addition of CA to β-CD/IBU does not significantly increase the solubility rate of IBU, it must be considered that the amount of β-CD is significantly less in the ternary complex compared to the binary β-CD/IBU.

25 March 2025 in Gels
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Journal Article
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MSMarin Simeonov
Marin Simeonov
YYYoanna Yildirim
Yoanna Yildirim
CTChristo Tzachev
Christo Tzachev
EVElena Vassileva
Elena Vassileva
Hydrogels with tunable properties are of great interest for the development of advanced drug delivery systems. In this study, novel hydrogels with an interpenetrating polymer network (IPN) structure were obtained from the pH-responsive poly(methacrylic acid) (PMAA) and the neutral poly(N,N-dimethylacrylamide) (PDMAM). The newly synthesized IPN hydrogels were shown to be pH responsive with a 1.5 to 2.5 fold increase in their equilibrium swelling ratio at a pH above 5 which makes them appropriate for targeted intestine drug delivery. Moreover, their pH responsiveness was found to be strongly influenced by the IPN’s composition. The IPN hydrogels were loaded with PMH via swelling and the drug entrapment efficiency was found to depend on their swelling characteristic varying with the IPN’s composition from 20% to 60%. The drug release profiles were investigated under conditions resembling the oral route of drug application. The PMH release profiles appeared to follow Fickian diffusion at a stomach-like pH = 1.2 and sub-diffusion mechanism at an intestine-like pH = 6.8. The results from this study reveal that IPN hydrogels of PMAA and PDMAM are promising candidates for oral delivery of promethazine hydrochloridee demonstrating pH responsiveness and controllable swelling dependent on their composition. Further investigations are planned to fully reveal their potential as smart drug delivery systems.

31 August 2024 in Pharmaceuticals
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Journal Article
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IKIskra Z. Koleva
Iskra Z. Koleva
CTChristo Tzachev
Christo Tzachev
Herein, we present an elegant and simple method for significant improvement of eugenol water solubility using the polymers Soluplus® and Lutrol F 127 as carriers and spray drying as an encapsulation method. The formulations were optimized by adding myo-inositol—a sweetening agent—and Aerosil® 200 (colloidal, fumed silica)—an anticaking agent. The highest encapsulation efficiency of 97.9–98.2% was found for the samples containing 5% eugenol with respect to the mass of Soluplus®. The encapsulation efficiencies of the spray-dried samples with 15% eugenol are around 90%. Although lowering the yield, the addition of Lutrol F 127 results in a more regular particle shape and enhanced powder flowability. The presence of Aerosil® 200 and myo-inositol also improves the rheological powder properties. The obtained formulations can be used in various dosage forms like powders, granules, capsules, creams, and gels.

21 December 2024 in Molecules
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Journal Article
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NINikolay Ishkitiev
Nikolay Ishkitiev
MMMaria Micheva
Maria Micheva
Marina Valerieva MitevaMarina Valerieva Miteva
Marina Valerieva Miteva
SGStefaniya Gaydarova
Stefaniya Gaydarova
CTChristo Tzachev
Christo Tzachev
AVAleksey Vasilev
Aleksey Vasilev
The development of fluorescence-based methods for bioassays and medical diagnostics requires the design and synthesis of specific markers to target biological microobjects. However, biomolecular recognition in real cellular systems is not always as selective as desired. A new concept for creating fluorescent biomolecular probes, utilizing a fluorogenic dye and biodegradable, biocompatible nanomaterials, is demonstrated. The synthesis of a new dicationic asymmetric monomethine cyanine dye with benzo[d]thiazolium-N-propionamide and chloroquinoline end groups is presented. The photophysical properties of the newly synthesized dye were examined through the combined application of spectroscopic and theoretical methods. The applicability of the dye as a fluorogenic nucleic acid probe was proven by UV-VIS spectroscopy and fluorescence titration. The dye–nucleic acid interaction mode was investigated by UV-Vis and CD spectroscopy. The newly synthesized dicationic dye, like other similar fluorogenic structures, limited permeability, which restricts its use as a probe for RNA and DNA. To enhance cellular delivery, we utilized a patented technology that employs solid, insoluble lipid nanoparticles. This method ensures the complete introduction of the dye into cells while minimizing activity outside the cells. In our study involving two human cell lines, we observed improved penetration through the cell membrane and distinctive selectivity in visualizing nucleic acids within the cytoplasm and nucleus.

28 July 2025 in ChemRxiv
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Preprint
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EBEva Bittrich
Eva Bittrich
SBSusanne Boye
Susanne Boye
ZNZanelle Van Niekerk
Zanelle Van Niekerk
ZSZahn Stanvliet
Zahn Stanvliet
APArthur Portfetye
Arthur Portfetye
ALAlbena Lederer
Albena Lederer
Precise mapping of structural heterogeneity at the sub-10 nm scale is pivotal for rational nanoparticle design, yet convention-al analytical workflows remain inadequate. Here we integrate dilution-controlled asymmetric flow field-flow fractionation (AF4) with small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) to interrogate ellipsoidal solid–liquid lipid nanoparticles (LNPs). The dilution-controlled AF4 mode amplifies scattering contrast, enabling robust, shape-resolved analysis across entire elution profiles. Coupling AF4 to SANS in D₂O further sharpens resolution for the smallest fractions by reducing particle diffusion through increased solvent viscosity. Comparative sizing shows that SAXS/SANS accurately capture primary particles down to ~5 nm, whereas multi-angle light scattering chiefly detects loosely associated aggregates. Morphology profiling reveals that surfactant identity governs particle shape, polydispersity, and overall architec-ture. Joint SAXS/SANS modelling uncovers a 2–3 nm polar shell enveloping the hydrophobic lipid core. Together, these insights refine our understanding of LNP size and morphology and establish dilution-controlled AF4-SAXS/SANS as a high-resolution platform for dissecting complex nanoparticle systems relevant to biomedical applications.

23 June 2025 in Pharmaceuticals
Verified
Journal Article
Open access
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IKIskra Z. Koleva
Iskra Z. Koleva
KKKatya Kamenova
Katya Kamenova
Petar Dimitrov PetrovPetar Dimitrov Petrov
Petar Dimitrov Petrov
CTChristo Tzachev
Christo Tzachev
Background/Objectives: In this study, we present a green, scalable platform for the production of water-dispersible powders co-encapsulating the lipophilic bioactives curcumin (Cur) and eugenol (Eug) within the amphiphilic polymer Soluplus® (SP) via low-temperature spray drying. Methods: The amount of Cur (1%, 5%, and 10%) and Eug (5%, 10%, 15%, and 20%) was varied to achieve single- and double-loaded water-soluble powders with the maximum amount of active substances. The powders containing a higher loading of Cur, 5% and 10% (and Eug), were obtained from water/ethanol mixtures (2:1 and 5:1 v/v ratio), while the formulation with 1% of Cur was spray-dried by using water as a solvent. Results: By leveraging aqueous or aqueous–ethanolic feed systems, we achieved high loading of the bioactive substances—up to 10% Cur and 20% Eug (w/w)—while minimizing organic solvent use. Myo-inositol was incorporated as a stabilizing excipient to modulate particle morphology, improve powder flowability, and enhance redispersibility. Physicochemical characterization revealed nanoscale micellization (53–127 nm), amorphization of both actives as confirmed by XRD and DSC, and the absence of crystalline residue. Encapsulation efficiencies exceeded 95% for Cur and 93% for Eug. Dissolution tests demonstrated a rapid release from the 5% Cur/5% Eug formulation (>85% in 5 min), while higher-loaded single-formulations showed progressively slower release (up to 45 min). Conclusions: This work demonstrates a robust and environmentally responsible encapsulation strategy, suitable for delivering poorly water-soluble phytochemicals with potential applications in oral nutraceuticals and pharmaceutical dosage forms.