Marco Consumi

A PVA/PVP hydrogel for human lens substitution: Synthesis, rheological characterization, and in vitro biocompatibility

To overcome opacification and absence of accommodation of human lens substitutes a new poly(vinyl alcohol) (PVA)/poly(N-vinyl-2- pyrrolidinone) (PVP) based hydrogel (PPS31075) was realised. The Infrared Spectroscopy and the mechanical spectra confirmed the successful occurrence of crosslinking reaction. The rheological analysis pointed out a behavior comparable with that of young human lens in terms of complex shear modulus and accommodation capability. Further analysis in terms of optical properties, water content measurements, diffusion coefficient, cytotoxicity, and human capsular cell adhesion confirmed the applicability of such a hydrogel as potential human lens substitute.

Dependence of water uptake and morphology of hyaluronan‐ and alginate‐based hydrogels on pH and degree of crosslinking

Hydrogels of alginate and hyaluronan with 5%, 50% and 100% crosslinking, (percentage of polysaccharide carboxylate groups involved in crosslinking) are synthesized. Crosslinking and stoichiometry were varied by appropriate addition of chloromethylpyridine iodide (CMPI) to activate the carboxylic groups. Crosslinking percentage was determined by potentiometry, i.e., titrating the free carboxylate groups of the polysaccharide. Water uptake by the gels is studied in relation to crosslinking and pH. Hydrogen bonds in the three-dimensional network, as shown by FT-IR spectroscopy, are used to explain differences in water uptake and their dependence on pH. Scanning electron microscopy (SEM) analysis of the gels is performed at different pHs and the morphologies are com- pared with their chemical structures.

In Vitro Biocompatibility of New PVA-Based Hydrogels as Vitreous Body Substitutes

In order to synthesize injectable hydrogels suitable as vitreous body substitutes, a new method based on the use of trisodium trimetaphosphate (STMP) to cross-link PVA was recently proposed. Hydrogels with different molar ratios between STMP and PVA were realised. The aim of the present study was the evaluation of the biocompatibility of the different STMP/PVA hydrogels synthesised by analysing the effects of their in vitro interaction with cultures of mouse fibroblasts NIH3T3, primary human microvascular endothelial cells adult (HMVECad) and human lens cells. Cytotoxicity of hydrogels was first evaluated by analysing cell density and proliferation. Morphological and morphometric analysis of cell in contact with hydrogels was then performed using light microscopy and scanning electron microscopy, respectively. Moreover, cell adhesion and growth onto the hydrogels surface was evaluated and correlated to the amount of adsorbed proteins. At last, the biocompatibility of the sheared STMP/PVA 1:8 hydrogel was tested. The in vitro data of all the STMP/PVA hydrogels demonstrated their good biocompatibility, and indicated that the 1:8 sample was the most promising as vitreous body substitute.

Different Factors Affecting Human ANP Amyloid Aggregation and Their Implications in Congestive Heart Failure

Aims Atrial Natriuretic Peptide (ANP)-containing amyloid is frequently found in the elderly heart. No data exist regarding ANP aggregation process and its link to pathologies. Our aims were: i) to experimentally prove the presumptive association of Congestive Heart Failure (CHF) and Isolated Atrial Amyloidosis (IAA); ii) to characterize ANP aggregation, thereby elucidating IAA implication in the CHF pathogenesis. Methods and Results A significant prevalence (85%) of IAA was immunohistochemically proven ex vivo in biopsies from CHF patients. We investigated in vitro (using Congo Red, Thioflavin T, SDS-PAGE, transmission electron microscopy, infrared spectroscopy) ANP fibrillogenesis, starting from α-ANP as well as the ability of dimeric β-ANP to promote amyloid formation. Different conditions were adopted, including those reproducing β-ANP prevalence in CHF. Our results defined the uncommon rapidity of α-ANP self-assembly at acidic pH supporting the hypothesis that such aggregates constitute the onset of a fibrillization process subsequently proceeding at physiological pH. Interestingly, CHF-like conditions induced the production of the most stable and time-resistant ANP fibrils suggesting that CHF affected people may be prone to develop IAA. Conclusions We established a link between IAA and CHF by ex vivo examination and assessed that β-ANP is, in vitro, the seed of ANP fibrils. Our results indicate that β-ANP plays a crucial role in ANP amyloid deposition under physiopathological CHF conditions. Overall, our findings indicate that early IAA-related ANP deposition may occur in CHF and suggest that these latter patients should be monitored for the development of cardiac amyloidosis.

Biological performance of two materials based on sulfated hyaluronic acid and polyurethane

Polyurethane bound with sulfated hyaluronic acid was synthesized by two different chemical routes. Both the materials obtained consist of a hydrophilic component, sulfated hyaluronic acid (HyalS 3.5 ), and a hydrophobic component, polyurethane (PU). In the material named Puhmdi, the HyalS 3.5 was cross-linked to the PU chains via hexamethylene diisocyanate (HMDI) while in that named Pubrac, the binding of HyalS 3.5 to the PU chains occurred only through a few carboxy groups viaN,N′-dicyclohexylcarbodiimide (DCC) and bromoacetic acid.The surface characteristics of the polymers were investigated by ATR FT-IR spectroscopy while the surface morphology was analyzed by scanning electron microscopy.There was a significant difference between the surface characteristics of the films in dry and hydrated environments. In both materials the hydrophilic component (HyalS 3.5 ) migrates from the bulk to the surface, thus minimizing the surface free energy of the polymer when exposed to the hydrated environment. The different biological behavior of the two materials was demonstrated with the thrombin time test and platelet adhesion test. Pubrac inhibits the coagulation process while Puhmdi does not.

Effect of resveratrol on platelet aggregation by fibrinogen protection

The effect of resveratrol (RSV) in inhibiting platelet adhesion and aggregation, as well as fibrinogen (FBG) conformational changes promoted by epinephrine (EP), were studied, by using complementary experimental techniques. NMR and IR spectroscopies were used to investigate possible protective effects by RSV towards FBG, in presence of EP. The protective effect of RSV towards FBG was highlighted by spin nuclear relaxation experiments that were interpreted for determining the thermodynamic equilibrium constants of FBG-EP interaction, and by infrared measurements, that showed EP-induced conformational changes of FBG. The ability of RSV in inhibiting platelet adhesion and aggregation promoted by EP was evaluated by scanning electron microscopy (SEM), measuring the platelet adhesion and aggregation degree, in comparison to data obtained for platelet aggregation in platelet rich plasma (PRP). The experimental combined approach pointed out that RSV is able to protect both FBG and platelets from the denaturant and aggregating action of EP at stress level concentration.

Protective effect of quercetin and rutin encapsulated liposomes on induced oxidative stress

Natural antioxidants show many pharmacological properties, but poor solubility and inability to cross cell membrane. Liposomes are biocompatible and phospholipid vesicles able to carry hydrophilic, hydrophobic, and amphiphilic molecules. This paper focus on the synthesis of anionic, cationic and zwitterionic liposomes, loaded with quercetin or rutin, and on the evaluation of their cytotoxicity and protective effects against oxidative stress. Chemical characterization was obtained by dynamic light scattering and z-potential experiments. In vitro cell behavior was evaluated by Neutral Red Uptake test. All liposomes, empty and loaded with antioxidants, are stable. The cytotoxicity of both quercetin and rutin encapsulated in zwitterionic and anionic liposomes is higher than that of their solutions. Quercetin and rutin loaded in cationic liposomes are able to inhibit the toxic effect of empty liposomes. The encapsulation of rutin at 5.0×10-5 and 5.0×10-4M, in zwitterionic and anionic liposomes, protects fibroblasts by H2O2 treatment, while the loading with quercetin does not have effect on improving cell viability. All data suggest that the tested liposomes are stable and able to include quercetin and rutin. The liposomes encapsulation of antioxidants makes easier their internalization by cells. Moreover, zwitterionic and anionic liposomes loaded with rutin protect cells by oxidative stress. Liposomes stability together with their good in vitro cytocompatibility, both empty and loaded with antioxidant molecules, makes these systems suitable candidates as drug delivery systems. Moreover, the encapsulation of rutin, is able to protect cells by oxidative stress.

Alginate–gelatin formulation to modify lovastatin release profile from red yeast rice for hypercholesterolemia therapy

AIM The preparation of a delivery system able to guarantee a delayed release of lovastatin from red yeast rice (RYR) is mandatory to counteract cholesterol biosynthesis effectively. MATERIALS & METHODS Polymeric formulations were prepared mixing alginate and gelatin, in different ratios, with RYR. The effect of different composition on stiffness, viscosity, swelling behavior and mesostructure of matrices was analyzed. RESULTS Formulations obtained combining polymers in comparable amount (i.e., 60/40 and 50/50) guaranteed a delayed release of lovastatin from RYR, a prolonged inhibitory activity toward 3-hydroxy-3-methylglutaryl-coenzyme A reductase and a decreased cholesterol synthesis. CONCLUSION The formulation obtained combining 60% gelatin and 40% of alginate showed physicochemical properties suitable to lead a lovastatin release profile compatible with cholesterol biosynthesis.

Homogentisic acid induces morphological and mechanical aberration of ochronotic cartilage in alkaptonuria: BERNARDINI et al.

Alkaptonuria (AKU) is a disease caused by a deficient homogentisate 1,2‐dioxygenase activity leading to systemic accumulation of homogentisic acid (HGA), that forms a melanin‐like polymer that progressively deposits onto connective tissues causing a pigmentation called “ochronosis” and tissue degeneration. The effects of AKU and ochronotic pigment on the biomechanical properties of articular cartilage need further investigation. To this aim, AKU cartilage was studied using thermal (thermogravimetry and differential scanning calorimetry) and rheological analysis. We found that AKU cartilage had a doubled mesopore radius compared to healthy cartilage. Since the mesoporous structure is the main responsible for maintaining a correct hydrostatic pressure and tissue homoeostasis, drastic changes of thermal and rheological parameters were found in AKU. In particular, AKU tissue lost its capability to enhance chondrocytes metabolism (decreased heat capacity) and hence the production of proteoglycans. A drastic increase in stiffness and decrease in dissipative and lubricant role ensued in AKU cartilage. Multiphoton and scanning electron microscopies revealed destruction of cell–matrix microstructure and disruption of the superficial layer. Such observations on AKU specimens were confirmed in HGA‐treated healthy cartilage, indicating that HGA is the toxic responsible of morphological and mechanical alterations of cartilage in AKU.

Hybrid PVA-xanthan gum hydrogels as nucleus pulposus substitutes

Abstract Hybrid hydrogels were synthesized mixing poly(vinyl alcohol) (PVA) and xanthan gum (XG) in different molar ratios and using trisodium trimetaphosphate, as crosslinking agent, to obtain potential nucleus pulposus substitutes. Human Nucleus Pulposus (NP) is a hydrogel-like tissue with peculiar properties, which determine its role in supporting and dissipating spinal loads. Hydrogel obtained mixing PVA and XG in molar ratio 4:1 (PX25) showed mechanical, swelling, and thermal properties, i.e., heat capacity, which make it a good candidate as a potential NP substitute. Preliminary cytotoxicity tests pointed out that the developed materials did not show any signs of cytotoxicity towards NIH3T3 cells. Graphical Abstract