Polyhydroxybutyrate-Based Nanocomposites for Bone Tissue Engineering

Bone-related diseases have been increasing worldwide, and several nanocomposites have been used to treat them. Among several nanocomposites, polyhydroxybutyrate (PHB)-based nanocomposites are widely used in drug delivery and tissue engineering due to their excellent biocompatibility and biodegradability. However, PHB use in bone tissue engineering is limited due to its inadequate physicochemical and mechanical properties. In the present work, we synthesized PHB-based nanocomposites using a nanoblend and nano-clay with modified montmorillonite (MMT) as a filler. MMT was modified using trimethyl stearyl ammonium (TMSA). Nanoblend and nano-clay were fabricated using the solvent-casting technique. Inspection of the composite structure revealed that the basal spacing of the polymeric matrix material was significantly altered depending on the loading percentage of organically modified montmorillonite (OMMT) nano-clay. The PHB/OMMT nanocomposite displayed enhanced thermal stability and upper working temperature upon heating as compared to the pristine polymer. The dispersed (OMMT) nano-clay assisted in the formation of pores on the surface of the polymer. The pore size was proportional to the weight percentage of OMMT. Further morphological analysis of these blends was carried out through FESEM. The obtained nanocomposites exhibited augmented properties over neat PHB and could have an abundance of applications in the industry and medicinal sectors. In particular, improved porosity, non-immunogenic nature, and strong biocompatibility suggest their effective application in bone tissue engineering. Thus, PHB/OMMT nanocomposites are a promising candidate for 3D organ printing, lab-on-a-chip scaffold engineering, and bone tissue engineering.

Defects and defect engineering in Soft Matter

Soft matter covers a wide range of materials based on linear or branched polymers, gels and rubbers, amphiphilic (macro)molecules, colloids, and self-assembled structures. These materials have applications in various industries, all highly important for our daily life, and they control all biological functions; therefore, controlling and tailoring their properties is crucial. One way to approach this target is defect engineering, which aims to control defects in the material's structure, and/or to purposely add defects into it to trigger specific functions. While this approach has been a striking success story in crystalline inorganic hard matter, both for mechanical and electronic properties, and has also been applied to organic hard materials, defect engineering is rarely used in soft matter design. In this review, we present a survey on investigations on defects and/or defect engineering in nine classes of soft matter composed of liquid crystals, colloids, linear polymers with moderate degree of branching, hyperbranched polymers and dendrimers, conjugated polymers, polymeric networks, self-assembled amphiphiles and proteins, block copolymers and supramolecular polymers. This overview proposes a promising role of this approach for tuning the properties of soft matter.

Effect of various formulation ingredients on thermal characteristics of PVC/clay nanocomposite foams: experimental and modeling

The effect of various ingredients – nanoclay (NC), azodicarbonamaide (ADCA), paraloeid K-400 and calcium stearate (Ca.St) – on thermal behavior of melt blended poly (vinyl chloride)/NC nanocomposites was investigated. Combinations of two artificial intelligence algorithms were performed for modeling of the systems. The formulation ingredients affect the thermal features of the compounds. Upon increasing the effect of various ingredients, i.e. NC, ADCA, K-400 and Ca.St, an increase in ash content was observed, hence, the thermal stability increased. The effect of ingredients on initial degradation temperature (T5%) and half degradation temperature (T50%) was not obvious. The artificial neural network (model) and the clonal selection algorithm (optimizer) were performed for proper modeling of the systems. These models were used to determine the role of T5%, T50% and char based on the contents of ingredients. The result successfully modeled the process parameters.

A study on obtaining nonwovens using polyhydroxyalkanoates and the melt-blown technique

Poly(3-hydroxybutyrate) [P(3HB)] nonwovens were obtained from polymers enriched with nucleants using the melt-blown technique. The most important physico-mechanical parameters, susceptibility to hydrolytic degradation (in neutral and alkaline medium) and to biodegradation, were analysed for the obtained nonwovens. It was determined that P(3HB) nonwovens, compared to popular polypropylene (PP) nonwovens, are characterized by elementary fibres with several times greater average diameter, greater mass per unit area and greater air permeability value. P(3HB) nonwovens are, on average, seven times more susceptible to breakage, and their elongation at maximum force is more than 50 times smaller than that for PP nonwovens. Hydrolysis of P(3HB) nonwovens is faster in an alkaline than in a neutral medium, and the observed relationships led to the conclusion that, at the start, short chains are subject to hydrolysis. Analysis of the weight loss associated with the degradation in bioreactors showed that P(3HB) nonwovens are more susceptible to biodegradation under anaerobic than under aerobic conditions.

Effect of Organo-Modified Nanoclay on the Thermal and Bulk Structural Properties of Poly(3-hydroxybutyrate)-Epoxidized Natural Rubber Blends: Formation of Multi-Components Biobased Nanohybrids

Multi-component nanohybrids comprising of organo-modified montmorillonite (MMT) and immiscible biopolymer blends of poly(3-hydroxybutyrate) (PHB) and epoxidized natural rubber (ENR-50) were prepared by solvent casting technique. The one and three dimensional morphology of PHB/ENR-50/MMT systems were studied using Polarizing Optical Microscopy (POM) and Scanning Electron Microscopy (SEM). Differential scanning calorimetry (DSC) technique was used to evaluate the thermal properties of the nanohybrids. The melting temperature (Tm) and enthalpy of melting (ΔHm) of PHB decrease with respect to the increase in ENR-50 as well as MMT content. The non-isothermal decomposition of the nanohybrids was studied using thermogravimetric (TG-DTG) analysis. FTIR-ATR spectra supported ring opening of the epoxide group via reaction with carboxyl group of PHB and amines of organic modifier. The reaction mechanism towards the formation of the nanohybrids is proposed.