This work presents a thermal evolution study of gels obtained by chelation of aluminum sec-butoxide (Asb) with ethyl acetoacetate (Eaa) in various amounts. Samples were characterized by scanning electron microscopy (SEM), low angle laser light scattering (LALLS), differential thermal and thermo-gravimetric analysis (DTA/TGA), Fourier-transformed infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). It was established that samples with a low Eaa/Asb ratio are mainly amorphous, whilst the samples with greater Eaa/Asb ratio are predominantly chelate. The crystallization of γ-Al2O3 takes place between 600 and 1000 °C in two separate processes for all investigated samples. On the other hand, a complete transition to α-Al2O3 at 1200 °C occurs exclusively in samples with high Eaa/Asb ratio, while it is only partial for samples with low Eaa/Asb ratio. The observed mass loss is in concordance with the hypothesis that the overall gel content in the samples could be represented by a simplified formula Al(Eaa)xO(3−x)/2, where x is the Eaa/Asb ratio. In addition to thermal evolution, the gel-chelate duality of the samples is reflected in the morphology and particle size distribution.
Azithromycin (AZT) encapsulated into various types of liposomes (AZT-liposomes) displayed pronounced in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA) (1). The present study represents a follow-up to this previous work, attempting to further explore the anti-MRSA potential of AZT-liposomes when incorporated into chitosan hydrogel (CHG). Incorporation of AZT-liposomes into CHG (liposomal CHGs) was intended to ensure proper viscosity and texture properties of the formulation, modification of antibiotic release, and enhanced antibacterial activity, aiming to upgrade the therapeutical potential of AZT-liposomes in localized treatment of MRSA-related skin infections. Four different liposomal CHGs were evaluated and compared on the grounds of antibacterial activity against MRSA, AZT release profiles, cytotoxicity, as well as texture, and rheological properties. To our knowledge, this study is the first to investigate the potential of liposomal CHGs for the topical localized treatment of MRSA-related skin infections. CHG ensured proper viscoelastic and texture properties to achieve prolonged retention and prolonged release of AZT at the application site, which resulted in a boosted anti-MRSA effect of the entrapped AZT-liposomes. With respect to anti-MRSA activity and biocompatibility, formulation CATL-CHG (cationic liposomes in CHG) is considered to be the most promising formulation for the treatment of MRSA-related skin infections.
The widespread use of antibiotics can result in the release of a large number of residues into the environment. In order to reduce the exposure risk, considerable research has been carried out in the field of antibiotic residues. We aim to explore the possibilities of antibiotic amoxicillin biodegradation in laboratory scale by adding microbiological cultures, Pseudomonas aeruginosa (Gram-negative) and Bacillus subtilis (Gram-positive), which are a type of bacteria that are commonly found in the environment, such as in soil and water. Apart from the degradation itself, special attention was paid to the identification of antibiotic residues. The biodegradation process was investigated, revealing a 99.2 % degradation efficiency at amoxicillin concentration of 0.2 mg mL-1, and four degradation products were identified. For reaction monitoring and identification of degradation products, UHPLC and LC-MS analyses were performed. Furthermore, to provide additional evidence, the products were independently synthesized and then compared spectrometrically with the obtained biodegradation products. These results could provide new aspects to the behavior of amoxicillin, and pave the way for further monitoring and studies of its residues in the environment.
Procesna analitička tehnologija (PAT) sve se češće primjenjuje u procesu kristalizacije za kontinuirano praćenje neke od ključnih procesnih veličina i značajki kvalitete proizvoda. Vrlo bitne procesne varijable za kristalizaciju hlađenjem su temperatura i koncentracija otopine. Kontinuirano mjerenje koncentracije omogućeno je naprednim in situ spektroskopskim instrumentima. U takve metode spada i prigušena ukupna reflektancija Fourier transformacijske infracrvene spektroskopije (engl. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy, ATR-FTIR), primijenjena u ovom istraživanju. U ovom radu razvijeni su kemometrijski modeli za kontinuiranu procjenu koncentracije otopine u stvarnom vremenu metodama strojnog učenja. Cilj ovog rada bio je razviti i ispitati modele parcijalne regresije metodom najmanjih kvadrata (engl. Partial Least Squares Regression, PLSR) i modele neuronskih mreža (engl. Neural Networks, NN) za modeliranje ovisnosti koncentracije djelatne tvari, ksilometazolin hidroklorid, u n-butanolu, o temperaturi i spektralnim podatcima dobivenim mjerenjima ATR-FTIR spektrometrom. U radu je provedena predobrada prikupljenih podataka tehnikom MSC (engl. Multiplicative Scatter Correction) te je provedeno skaliranje podataka prema normalizacijama Min-Max i Z-score. Analiziran je broj neurona u prvom i drugom skrivenom sloju, broj skrivenih slojeva, vrsta primijenjenog algoritma učenja (ADAM, NADAM, RMSprop) kao i utjecaj vrste prijenosne funkcije (ReLU, sigmoid, tanh) na kvalitetu razvijenih neuronskih mreža. Razvijeni modeli na sva četiri skupa podataka dali su iznimno dobre rezultate s obzirom na iznose koeficijenta determinacije i srednje kvadratne pogreške. Modelom neuronske mreže dobiveni su koeficijenti determinacije u rasponu vrijednosti od 0,9979 do 0,9989, dok je srednja kvadratna pogreška od 0,0020 do 0,0011. PLSR modelom dobiveni su koeficijenti determinacije od 0,9990 do 0,9995, odnosno srednja kvadratna pogreška od 0,0009 do 0,0005. Dobiveni rezultati pokazali su da predobrada podataka i dodavanje drugoga skrivenog sloja neuronske mreže u ovoj studiji nisu imali velik utjecaj na konačne rezultate. Takav način praćenja i kontrole procesa rezultira efikasnijom proizvodnjom uz smanjenu vjerojatnost pogreške, što u konačnici farmaceutskoj industriji omogućuje brže plasiranje proizvoda na tržište.
The everyday use of various pharmaceuticals to treat humans or animals means that they are increasingly found in the environment. Contamination of the soil can cause the active ingredients to be strongly sorbed to the soil or sediment. In the worst case, they can also be expected to occur in the aquatic environment due to their different polarity. In this study, four drugs from different therapeutic classes (trimetoprim, memantine, cefdinir, praziquantel) were used in dissolved form in two sediment and three soil samples to obtain data that can describe their fate and behavior in the environment. The sorption affinities of the pharmaceuticals were described using linear, Freundlich and Dubinin-Radushkevich sorption isotherms. The highest Kd values were obtained for cefdinir, while memantine and praziquantel tended to be present in water due to their very low sorption coefficients. The studied influence of pH showed a negative trend for memantine and trimetoprim, while an increase in ionic strength resulted in higher Kd values for all drugs. The sorption mechanism for all tested samples was best described by the pseudo-secondary kinetic model (R2 > 0.9999).
