Ciprofloxacin-collagen conjugate in the wound healing treatment

The synthesis of a novel functional biomaterial for wound healing treatment was carried out by adopting a free-radical grafting procedure in aqueous media. With this aim, ciprofloxacin (CFX) was covalently incorporated into collagen (T1C) chains employing an ascorbic acid/hydrogen peroxide redox pair as biocompatible initiator system. The covalent insertion of CFX in the polymeric chains was confirmed by FT-IR and UV analyses, while an antibacterial assay demonstrated the activity of the synthesized conjugate against Staphylococcusaureus and Escherichia coli, microorganisms that commonly infect wounds. A catechin blended conjugate was also tested in order to evaluate the ability to influence fibroblast cell growth. The observed antibacterial activity and stimulation of fibroblast growth support the applicability of CFX-T1C conjugate in wound treatment encouraging the healing process.

Quercetin-imprinted nanospheres as novel drug delivery devices

In this work, molecularly imprinted nanospheres for controlled/sustained release of quercetin were synthesized employing methacrylic acid and ethylene glycoldymethacrylate as functional monomer and crosslinking agent, respectively. One pot precipitation polymerization was chosen as polymerization technique to obtain nanosized materials with spherical shape. Morphological and hydrophilic properties by scanning electron microscopy and water content measurements were determined, and recognition and selectivity properties of the imprinted materials were tested using the template quercetin and its structural analogue, the flavonoid catechin. Finally, the applicability of the obtained materials as drug delivery devices was evaluated by performing in vitro release studies in plasma simulating fluids and cytotoxicity testson HeLa cells.

Synthesis, characterization and in-vitro antitubercular activity of isoniazid-gelatin conjugate

OBJECTIVES

A novel and simple method to synthesize antitubercular-protein conjugate by solid phase synthesis was developed employing a carboxypolystyrene resin. The aim was to covalently bind a drug with antitubercular activity, isoniazid, to a biomacromolecule, gelatin, widely used in the pharmaceutical, cosmetic and food industry.

METHODS

Calorimetric and (1) H NMR analyses were performed to verify the bond formation between the antitubercular drug and gelatin. After absorption isoniazid delivers toxic metabolites and so an oxidation test with tert-butyl hydroperoxide was performed to assess the amount of toxic metabolites released from the prodrug (gelatin linked to isoniazid), compared with isoniazid itself.

KEY FINDINGS

  Spectrophotometric analysis revealed that the protein derivative was an excellent isoniazid prodrug since there was a 40% reduction in release of toxic metabolites (isonicotinic acid) by the prodrug. The results clearly showed that antitubercular moieties, covalently linked to a natural polymer, allowed the introduction of peculiar features for specific pharmaceutical applications into the macromolecule. In addition, antitubercular activity of the new polymer was determined by Middlebrook 7H11 medium against Mycobacterium tuberculosis complex.

CONCLUSIONS

The new isoniazid-gelatin conjugate showed significant antitubercular activity and for this reason should be useful as an efficacious tool in the treatment of tuberculosis.

Molecularly imprinted polymers in drug delivery: state of art and future perspectives

INTRODUCTION

Molecularly imprinted polymers (MIPs) are synthetic receptors, characterized by a high selectivity for the selected template. Among the different applications of MIPs, their use as controlled/sustained drug delivery devices has been extensively explored, even though the optimization of such devices needs to be performed before they are applied in clinical practice.

AREAS COVERED

Within drug delivery, one of the most promising fields is the possibility to modulate the drug release profile in response to a specific external stimulus; MIPs represent potentially suitable vehicles, because of the possibility to insert a stimuli-responsive co-monomer in their structure. This review discusses recent advances in the use of external stimuli to modulate drug release, as well as the synthetic strategies devoted to increase the water compatibility of these systems, which is a base requirement for their application in biomedicine.

EXPERT OPINION

Although it is easy to imagine imprinted polymers for biomedical applications, several aspects have to be further investigated, such as the in vivo studies, efficiency and biocompatibility. However, we think that in the next few years it will possible to see unprecedented progress in the preparation of such systems and the translational application of these intelligent structures in medicine.

Temperature-sensitive hydrogels by graft polymerization of chitosan and N-isopropylacrylamide for drug release

Thermo-responsive polysaccharidic hydrogels were designed and synthesized by a free radical induced grafting procedure. Chitosan was chosen as biopolymer to impart biocompatibility and biodegradability to the macromolecular systems, while N-isopropylacrylamide (NIPAAm) was selected as co-monomer responsive for the thermo-sensitive properties. Ammonium persulfate was the initiator system and different polymeric networks have been synthesized by modulating the amount of NIPAAm in the polymerization feed. The resulting hydrogels were proposed as drug delivery devices and their performance was evaluated by using Diclofenac sodium salt as a model drug. Hydrogels were carefully characterized by FT-IR spectrophotometry, calorimetric analyses and swelling behavior in a temperature range of 15-45°C. Finally, to verify the suitability of these hydrogels as thermo-responsive devices, the drug release profiles were studied performing in vitro experiments around the swelling-shrinking transition temperatures of the macromolecular systems.

A new method for the determination of biogenic amines in cheese by LC with evaporative light scattering detector

This paper presents a new LC method with evaporative light scattering detection (ELSD), for the separation and determination of the biogenic amines (histamine, spermidine, spermine, tyramine, putrescine and β-phenylethylamine) which are commonly present in cheese, as their presence and relative amounts give useful information about freshness, level of maturing, quality of storage and cheese authentication. The LC-ELSD method is validated by comparison of the results with those obtained through LC-UV determination, based on a pre-column dansyl chloride derivatisation step. The obtained data demonstrate that both methods can be interchangeably used for biogenic amines determination in cheese. The new LC-ELSD method shows good precision and permits to achieve, for standard solutions, limit of detection (LOD) values ranging from 1.4 to 3.6 mg L(-1) and limit of quantitation (LOQ) values ranging from 3.6 to 9.3 mg L(-1). The whole methodology, comprehensive of the homogenization-extraction process and LC-ELSD analysis, has been applied in the analysis of a typical Calabria (Southern Italy) POD cheese, known as Caciocavallo Silano. The most aboundant amine found was histamine, followed, in decreasing order, by tyramine, spermine, putrescine, β-phenylethylamine and spermidine, for a total amount of 127 mg kg(-1). This value does not represent a possible risk for consumer health, according to the toxicity levels reported in literature and regarded as acceptable.

A new approach for the evaluation of niosomes as effective transdermal drug delivery systems

The central motivation for this study was to evaluate if the increased hydrophilic drug permeation across the skin, which is always observed in presence of vesicular systems, is dependent on the structural organization of niosomes, that are used to transport the active molecules, or if it is only dependent on the surfactant dual nature. To answer this question, non-ionic surfactants belonging to the class of Pluronic and sucrose esters were used both as components of niosomal systems or in the form of sub-micellar solutions. The obtained niosomes were characterized by their entrapment efficiency, size and morphology. The enhancing effect of niosomes on the ex vivo percutaneous penetration of a model drug was investigated using a Franz-type diffusion chamber and compared to that obtained by using sub-micellar solution of surfactant or achieving pretreatment of the skin with surfactants' sub-micellar solution or empty niosomes. The results suggest that the surfactants used in this study could be considered as percutaneous permeation enhancers only when they are in the form of drug-loaded vesicular systems: no percutaneous promotion was achieved by using sub-micellar solution containing free Sulfadiazine sodium salt or performing pretreatment with empty niosomes or sub-micellar solutions of the surfactant. In our experiments, only niosomes act as effective transdermal drug delivery systems.

Selective determination of melamine in aqueous medium by molecularly imprinted solid phase extraction

A molecularly imprinted polymer able to recognize melamine in partially aqueous medium was synthesized using methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linking agent. The bound specificity and selectivity of the obtained material were verified by performing binding experiments with melamine and its structural analogue, 2,4,6-trimethoxy-1,3,5-triazine, respectively, using different aqueous binding media. Finally, the ability of MIP to selectively extract melamine from two real samples, a food supplement and a freeze-dried meat sample, was demonstrated.

Antioxidant multi-walled carbon nanotubes by free radical grafting of gallic acid: new materials for biomedical applications

OBJECTIVES

To prove the possibility of covalently functionalizing multi-walled carbon nanotubes (CNTs) by free radical grafting of gallic acid on their surface with the subsequent synthesis of materials with improved biological properties evaluated by specific in-vitro assays.

METHODS

Antioxidant CNTs were synthesized by radical grafting of gallic acid onto pristine CNTs. The synthesis of carbon nanotubes was carried out in a fixed-bed reactor and, after the removal of the amorphous carbon, the grafting process was performed. The obtained materials were characterized by fluorescence and Fourier transform infrared spectroscopy (FT-IR) analyses. After assessment of the biocompatibility and determination of the disposable phenolic group content, the antioxidant properties were evaluated in terms of total antioxidant activity and scavenger ability against 2,2'-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and peroxyl radicals. Finally the inhibition activity on acetylcholinesterase was evaluated.

KEY FINDINGS

  The covalent functionalization of CNTs with gallic acid was confirmed and the amount of gallic acid bound per g of CNTs was found to be 2.1±0.2 mg. Good antioxidant and scavenging properties were recorded in the functionalized CNTs, which were found to be able to inhibit the acetylcholinesterase with potential improved activity for biomedical and pharmaceutical applications.

CONCLUSIONS

For the first time, a free radical grafting procedure was proposed as a synthetic approach for the covalent functionalization of CNTs with an antioxidant polyphenol.

Characterization of the S-denitrosylating activity of bilirubin

Bilirubin-IX-alpha (BR) is an endogenous molecule with a strong antioxidant feature due to its ability to scavenge free radicals. In this paper, we demonstrated that BR, at concentrations close to those found within the cell (0.1-2.5 microM), acted as a denitrosylating agent and increased the release of nitric oxide from S-nitrosoglutathione (GSNO) and S-nitrosocysteine (SNOC) (2.5 microM). The complexation of BR with saturating concentrations of human serum albumin (HSA, 2.5 microM) did not further increase nitric oxide release from GSNO and SNOC. At concentrations similar to those reached in plasma (5-20 microM), BR denitrosylated S-nitroso-HSA (2.5 microM), the main circulating S-nitrosothiol, and this effect was potentiated by the complexation of BR with saturating HSA (20 microM). Furthermore, the product(s) of the reaction between nitric oxide and BR were identified. Ultraviolet and mass spectrometry analysis revealed that nitric oxide binds to BR forming a N-nitroso derivative (BR-nitric oxide) with extinction coefficients of 1.393 mM(-1)cm(-1) and 2.254 mM(-1)cm(-1) in methanol and NaOH, respectively. The formation of BR-nitric oxide did not occur only in a reconstituted system, but was confirmed in rat fibroblasts exposed to pro-oxidant stimuli. These results provided novel insights on the antioxidant characteristic of BR through its interaction with nitric oxide, a gaseous neurotransmitter with a well-known dual effect, namely neuroprotective under physiological conditions or neurotoxic if produced in excess, and proposed BR-nitric oxide as a new biomarker of oxidative/nitrosative stress.

Synthesis of stimuli-responsive microgels for in vitro release of diclofenac diethyl ammonium

Thermal and dual stimuli-responsive microspheres (pH and temperature) were prepared by free radical polymerization of methacrylate bovine serum albumin (BSA-MA) as cross-linker and sodium methacrylate (NaMA) and/or N-isopropylacrylamide (NIPAAm), as hydrophilic/pH-sensitive and thermo-responsive monomers, respectively. Microgels were characterized by infrared spectroscopy, morphological analysis, particle size distribution and determination of swelling properties. The network density and the shape of the microgels were found to depend on the concentration of the reactive species in the polymerization feed. Thermal analyses were performed to determine lower critical solution temperature values, which become close to the body temperature by increasing the content of the hydrophilic moieties in the network. In order to test the preformed materials as drug carriers, in vitro release studies of Diclofenac diethyl ammonium salt were performed. For all the co-polymers, a predominant drug release in the collapsed state was observed, while below the microgel transition temperature, a drug release through the swollen network occurs. The data recorded during the release tests demonstrated that the pH of the surrounding environment influences the drug release more than the temperature of the imbibing medium.

Negative thermo-responsive microspheres based on hydrolyzed gelatin as drug delivery device

This paper deals with the synthesis of thermo-responsive microspheres with proteic structure exhibiting a transition temperature close to the body temperature. Temperature-sensitive hydrogels have attracted extensive interest due to their potential and promising applications in drug delivery field since they can undergo a rapid and reversible phase transition from a swollen to a shrunken state depending on environmental temperature. The hydrogels were synthesized by free-radical polymerization of hydrolyzed methacrylated gelatin (HGel-MA) and N,N'-methylenebisacrylamide as pro-hydrophilic multifunctional macromer and crosslinker, respectively, and N-isopropylacrylamide as thermo-responsive monomer. Thermal analyses showed negative thermo-responsive behavior for all compositions and, by increasing the content of the hydrophilic moieties in the network, the transition temperature raised to 36.9 degrees C, close to the physiological values. In order to test the materials as drug carriers, diclofenac sodium salt was chosen as model drug. Drug release profiles, in phosphate buffer solution (pH 7.0, 10(-3) M) at 25 and 40 degrees C, depend on the hydrogel's crosslinking degree and hydrophilic/hydrophobic balance in the polymeric network. For all formulations, in the shrunken state, the drug release percent values ranged from 80% to 100% after 24 h, and after 3 h, more than 60% of therapeutics was delivered. On the contrary, the swelling of the loaded microparticles produces, even after 30 h, a drug release percent of about 75%. By using semi-empirical equations, the release mechanism was extensively studied and the diffusional contribute was evaluated. The physico-chemical characteristics of thermo-responsive materials confirm the applicability of the microspheres as drug delivery device.