Nishter Nishad Fathima

Influence of PCL on the material properties of collagen based biocomposites and in vitro evaluation of drug release

Formulation of biodegradable collagen-poly-ε-caprolactone (PCL) based biomaterials for the sustained release of insulin is the main objective of the present work. PCL has been employed to modulate the physico-chemical behavior of collagen to control the drug release. Designed formulations were employed to statistically optimize insulin release parameter profile at different collagen to PCL molar ratios. Circular dichroism, thermoporometry, FTIR, impedance and scanning electron microscopy techniques have been employed to investigate the effect of PCL on hydration dynamics of the collagen molecule, which in turn changes the dissolution parameters of the drug from the systems. Drug entrapment efficiency has been found to be maximum for collagen to PCL molar ratio of 1:2 (>90%). In vitro dissolution test reveals that 99% of the drug was released from composite at collagen to PCL molar ratio of 1:3 and 1:4 within 2h, which indicates that hydrophobicity of the matrix results in weak interaction between lipophilic drug and carrier materials. The least burst release was observed for collagen to PCL molar ratio at 1:2 as synergistic interactions between collagen and PCL was maximum at that particular polymer-polymer ratios. The drug release data indicates super case-II transport of drug (n>1.0).

A gelatin based antioxidant enriched biomaterial by grafting and saturation: Towards sustained drug delivery from antioxidant matrix

Proteins grafted with antioxidant molecules have drawn much attention due to their increased life time and biocompatibility. When protein macromolecules are cross linked chemically and physically with antioxidant molecules, they can act as antioxidant biomaterials as well as scaffolds to release the antioxidant molecules by diffusion. In our work, we have attempted to release catechin molecules from the matrix of glutathione grafted gelatin. Conjugation of glutathione and cross linkage was done by carbodiimide method to achieve smaller pores in the gelatin matrix and the characterization was performed by means of FTIR-ATR and calorimetric analyses. The glutathione grafted gelatin (GGSH) has been shown to have more thermal stability and pores with lesser radii than blank gelatin (bGEL). Free radical scavenging activity of GGSH was also found to be more than that of bGEL. Catechin was added to GGSH and bGEL by physical blending in order to achieve short term release of antioxidant molecules. CD spectra revealed that significant conformational changes occurred in secondary structure of gelatin upon interaction with catechin. Slower rate of catechin release from GGSH reflected the influence of cross linkage and physical interactive forces on the drug release properties. We conclude that the mixture of catechin with GGSH can be a potent antioxidant biomaterial releasing catechin at slower rate than the mixture of catechin with bGEL.

Effect of UV irradiation on the physico-chemical properties of iron crosslinked collagen.

Collagen is the main component of connective tissue and finds immense applications as a biomaterial. In this study, effect of UV irradiation on collagen crosslinked with iron has been carried out. The physical and optical properties of crosslinked collagen affected by UV irradiation were analyzed using electrospectral and fluorescence studies. The electronic spectral studies showed that the photoproducts formed on UV radiation decrease in the presence of iron. Circular dichroic studies revealed that the conformational changes brought about in the protein due to UV irradiation have been reduced owing to the crosslinking with iron. However, prolonged irradiation does bring about conformational changes to the protein.

Elucidation of hydration dynamics of locust bean gum-collagen composites by impedance and thermoporometry.

The intricacy of the different parameters involved in the hydration dynamics of collagen influences its performance as biomaterials. This work presents the molecular motions of collagen originating from the solvents and locust bean gum (LBG), which reveal the changes in solvation dynamics of the biopolymers affecting the surface as well as interfacial properties. Water, as a probe liquid bound in collagen has been investigated using a combination of thermoporometry, ATR-FTIR, circular dichroic spectroscopy, dielectric spectroscopy and SEM to explore the influence of LBG on collagen with respect to static and dynamic behaviour. The relaxation process of collagen in the frequency range of 0.01 Hz to 10(5)Hz and thermoporometry results indicate that the interfacial hydration dynamics are dependent on the applied concentration of LBG. This investigation explicitly reflects the rearrangements of the structural water clusters around the charged amino acids of collagen. These results can be employed to redesign the approach towards the development of collagen based biomaterials.

Dielectric behavior of gelatine-glycosaminoglycans blends: an impedance analysis.

The dielectric behavior of the gelatine-GAGs based blend systems has been studied to understand the dynamic behavior of the water at the protein-GAGs interfaces which are relevant for tissue engineering application. Impedance (Z) and phase have been measured as a function of frequencies from 0.01 Hz to 100 kHz. GAGs tunes the ionic charge drift which initiates polarization mechanisms through charge accumulation at structural interfaces and creates conduction currents. The admittance results showed that at high frequency, the conductivity increases with increasing GAGs concentration indicating changes in hydration shell of the gelatine by the GAGs.

Dielectric behaviour and conformational stability of collagen on interaction with DNA.

Collagen-DNA interaction studies will aid in improving the stability of DNA against nucleases. In the present study, the effect of DNA on different physico-chemical properties of collagen like viscosity, conformation and dielectric behaviour has been studied. Increase of DNA concentration leads to the increment of viscosity of collagen at the pH 4 and 5, but the trend is reversed at the pH of 6 and 7 due to the formation of collagen fibrils. The temperature dependent CD spectroscopic studies for collagen-DNA conjugate showed that thermal stability of collagen is modulated with increasing molar concentration of DNA. It also shows that DNA interactions with collagen did not result in change in the triple helical structure of collagen. Impedance measurements show that the strength of ion pairs for different molar concentrations of collagen-DNA conjugates has changed. Nyquist plot for collagen-DNA conjugate posses higher Y″ at DNA concentration of 1:25 and 1:50 whereas at 1:1 and 1:10 lower Y″ than the native collagen have been observed. An understanding of this nature of the collagen-DNA interactions is helpful for gene delivery applications.

Thermoporometry and impedance analysis to study dynamics of water and polymer present in hydrogel

Though various conventional methods are available to explore hydrogels, they have drawbacks such as analysis in solid state and failure to give insights into individual components of hydrogel viz. water (dispersion medium) and hydrophilic polymers (dispersed phase). The combined study of porosity and dielectric nature of hydrogel succeeds, in this context, as it investigates both the components individually. In this study, we have taken well-known hydrogel system gelatin-polyvinyl alcohol (PVA) cross linked with genipin. Thermoporometry has been used to investigate the state of water and porosity whereas Alternative Current (AC) impedance analysis has been used to study about nature of polymers through dielectric properties in hydrogel. The influence of physic-chemical properties was examined with SEM and in vitro drug release using catechin. The study revealed that increasing concentration of PVA to gelatin has retained excessive bound water molecules exhibiting high polarity in each polymeric component. Further, it is shown that reduction in pore size and high reactivity with drug molecules have led to lower initial release and increase total amount of release. We conclude that non-conventional methods such as thermoporometry and AC impedance analysis yield more valuable information about hydrogel, which can aid in designing appropriate biomaterial for intended drug release.

Microfabrication of gelatin–polycaprolactone composites for customized drug delivery

Dynamic properties of water molecules present in the vicinity of protein are sensitive to its local conformational motions. Water mobility at the protein surface/interfaces is affected by its polar and charged groups, which are capable of anchoring water molecules through H-bonds. Differential scanning calorimetry, ATR-FTIR spectroscopy and circular dichroic analysis have been employed to substantiate the changes in hydration of gelatin, interacting with polycaprolactone. Enthalpy of denaturation and decrease in melting temperature indicate alteration in water-bridges around gelatin. In vitro drug release studies substantiate the influence of hydration on its release kinetics. These studies would aid in exploration of potential drug carrier.

Anti-oxidant enriched hybrid nanofibers: Effect on mechanical stability and biocompatibility

Despite being a favorable candidate in wound dressing, collagen based biomaterials possess inferior mechanical properties which limit their usage. Collagen based hybrid nanofibers with other polymers can enhance their mechanical strength as well as their biological properties. Herein, we report collagen-silk fibroin hybrid nanofibers incorporated with fenugreek, an antioxidant, as a bioactive wound dressing material. The nanofiber mats were characterized using various experimental techniques. From the results, it was found that an increase in silk fibroin content in nanofibers improves the fiber diameter and tensile strength. The nanofibers also showed good antioxidant properties estimated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay. Presence of collagen in the nanofibers enhanced the biocompatibility of the nanofibers. Fenugreek released from the matrix enhanced the migration of fibroblasts in vitro. In vivo studies showed that collagen-silk fibroin-fenugreek nanofibers enhanced the wound closure via minimal inflammation and early epithelialization than the untreated and silk fibroin-fenugreek nanofibers treated wounds. Our study suggests that the fenugreek incorporated collagen-silk fibroin nanofibers is a potential candidate for wound dressings in clinical applications.

An emulsion of pigmented nanoceria as a medicinal cosmetic

Formulating nanoparticle based cosmetics with medicinal values to protect skin from environmental stress is a challenging task nowadays. In our work, we have prepared an emulsion of bluish pigmented cerium oxide nanoparticles (nanoceria) with potent free radical scavenging activity. The nanoceria were prepared by conventional thermal decomposition, and encapsulated by the amine-containing polyethylenimine. Characterizations such as Nuclear Magnetic Resonances (NMR), Dynamic Light Scattering (DLS), Atomic Force Microscope (AFM), Transmission Electron Micrographs (TEM) and X-ray Diffractograms (XRD) showed that the nanoceria were near spherical, monodispersed and sized 3–10 nm. UV-vis analysis confirmed that the particles were pigmented whereas circular dichroism revealed that the secondary structure of collagen, a fibrillar protein present in skin, was not affected by the presence of these pigmented nanoceria. In vitro anti-oxidant assays showed that the pigmented nanoceria were more effective than non-pigmented nanoceria against nitrile and peroxy radicals, with their activity depending on the concentration of CeO2. Thus, the emulsion of pigmented nanoceria can be evaluated, in future, as a medicinal cosmetic for protecting the skin.