Nanometric Hydroxyapatite Particles as Active Ingredient for Bioinks: A Review

Additive manufacturing (AM), frequently cited as three-dimensional (3D) printing, is a relatively new manufacturing technique for biofabrication, also called 3D manufacture with biomaterials and cells. Recent advances in this field will facilitate further improvement of personalized healthcare solutions. In this regard, tailoring several healthcare products such as implants, prosthetics, and in vitro models, would have been extraordinarily arduous beyond these technologies. Three-dimensional-printed structures with a multiscale porosity are very interesting manufacturing processes in order to boost the capability of composite scaffolds to generate bone tissue. The use of biomimetic hydroxyapatite as the main active ingredient for bioinks is a helpful approach to obtain these advanced materials. Thus, 3D-printed biomimetic composite designs may produce supplementary biological and physical benefits. Three-dimensional bioprinting may turn to be a bright solution for regeneration of bone tissue as it enables a proper spatio-temporal organization of cells in scaffolds. Different types of bioprinting technologies and essential parameters which rule the applicability of bioinks are discussed in this review. Special focus is made on hydroxyapatite as an active ingredient for bioinks design. The goal of such bioinks is to reduce the constraints of commonly applied treatments by enhancing osteoinduction and osteoconduction, which seems to be exceptionally promising for bone regeneration.

Comparison of Hydroxypropylcellulose and Hot-Melt Extrudable Hypromellose in Twin-Screw Melt Granulation of Metformin Hydrochloride: Effect of Rheological Properties of Polymer on Melt Granulation and Granule Properties

High-molecular-weight hypromellose (HPMC) and hydroxypropyl cellulose (HPC) are widely known, extended-release polymers. Conventional high-molecular-weight HPMCs are preferred in extended-release applications but not widely used in twin-screw melt granulation due to processability difficulties at low operating temperatures and potential drug degradation if high processing temperatures are used. Conversely, high-molecular-weight grade HPC (Klucel®) can be used in melt granulation processes. The purpose of this study was to evaluate the processability and dissolution behavior of HPC GXF ((Klucel® GXF) and a recently introduced type of hot-melt extrudable HPMC (Affinisol®) in extended-release metformin hydrochloride formulations using twin-screw melt granulation. Powder blends were prepared with 75% w/w metformin HCl and 25% w/w polymeric binder. Blends were granulated at processing temperatures of 160, 140, 120 and 100 °C. HPMC HME 4M (Affinisol® 4M) provided a fine powder, indicating minimum granulation at processing temperatures lower than 160 °C, and the tablets obtained with these granules capped during tableting. In contrast, acceptable tablets could be obtained with HPC GXF at all processing temperatures. Rheological studies including capillary rheometry to measure steady shear rate viscosity, and rotational rheometry to obtain time and temperature superposition data, showed that HPC GXF had a greater thermoplasticity than HPMC HME 4M, which made granulation possible with HPC GXF at low temperatures. Tablets compressed with granules obtained at 160 °C with both binders showed comparable dissolution profiles. High-molecular-weight HPC GXF provided a better processability at low temperatures and adequate tablet strength for the melt granulation of metformin HCl.

Composites of Vegetable Oil-Based Polymers and Carbon Nanomaterials

Owed to current environmental concerns and crude oil price fluctuations, the design of feasible substitutes to petroleum-based polymeric materials is a major challenge. A lot of effort has been focused on transforming natural vegetable oils (VOs), which are inexpensive, abundant, and sustainable, into polymeric materials. Different nanofillers have been combined with these bio-based polymer matrices to improve their thermal, mechanical, and antibacterial properties. The development of multifunctional nanocomposites materials facilitates their application in novel areas such as sensors, medical devices, coatings, paints, adhesives, food packaging, and other industrial appliances. In this work, a brief description of current literature on polymeric nanocomposites from vegetable oils reinforced with carbon nanomaterials is provided, in terms of preparation, and properties. Different strategies to improve the nanomaterial state of dispersion within the biopolymer matrix are discussed, and a correlation between structure and properties is given. In particular, the mechanical, thermal, and electrical properties of these natural polymers can be considerably enhanced through the addition of small quantities of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphene (G), or its derivatives such as graphene oxide (GO) or fullerenes (C60). Finally, some current and potential future applications of these materials in diverse fields are briefly discussed.

Super-Adsorbent Hydrogels for Removal of Methylene Blue from Aqueous Solution: Dye Adsorption Isotherms, Kinetics, and Thermodynamic Properties

Removal of dyes through adsorption from wastewater has gained substantial interest in recent years, especially in development of hydrogel based adsorbents, owing to their easy use and economical nature. The aim of the present study was to design a super-adsorbent hydrogel based on sodium styrenesulfonate (NaSS) monomer for removal of dyes like methylene blue (MB). NaSS displays both an aromatic ring and strongly ionic group in its monomer structure that can enhance adsorption capacity. Poly(sodium styrenesulfonate-co-dimethylacrylamide) hydrogels were prepared by solution free radical polymerization using gelatin methacryloyl (GelMA) as crosslinker, creating a highly porous, three-dimensionally crosslinked polymer network contributing to higher swelling ratios of up to 27,500%. These super-adsorbent hydrogels exhibited high adsorption capacity of 1270 mg/g for MB adsorption with above 98% removal efficiency. This is the first report for such a high adsorption capacity for dye absorbance for NaSS-based hydrogels. Additionally, the adsorption kinetics using a pseudo-first-order and the Freundlich adsorption isotherm models for multilayer, heterogeneous adsorption processes has been reported. The adsorbents’ reusability was confirmed through 4 repeated cycles of desorption-adsorption. The results discussed herein illustrate that NaSS based chemistries can be used as an efficient option for removal of organic dyes from contaminated wastewater.

Aspects of the Synthesis of Poly(styrene-block-isobutylene-block-styrene) by TiCl4-Co-initiated Cationic Polymerization in Open Conditions

The cationic polymerization of isobutylene and its block copolymerization with styrene using DiCumCl/TiCl4/2,6-lutidine initiating system has been studied in open conditions. It was shown that a higher concentration of proton trap is required in open conditions as compared to the glove box technique in order to have good control over molecular weight and polydispersity. Polyisobutylenes with Mn ≤ 50,000 g mol−1 and low polydispersity (Đ ≤ 1.2) were prepared at [Lu] = 12 mM. The synthesis of poly(styrene-block-isobutylene-block-styrene) triblock copolymer (SIBS) in open conditions required the addition of proton trap into two steps, half at the beginning of the reaction and the second half together with styrene. Following this protocol, a series of triblock copolymers with different length of central polyisobutylene block (from Mn = 20,000 g mol−1 to 50,000 g mol−1) and side polystyrene blocks (Mn = 4000 g mol−1–9000 g mol−1) with low polydispersity (Đ ≤ 1.25) were synthesized. High molecular SIBS (Mn > 50,000 g mol−1) with low polydispersity (Đ < 1.3) containing longer polystyrene blocks (Mn > 6000 g mol−1) demonstrated higher tensile strength (~13.5 MPa).

Inter- and Intra-Hydrogen Bonding Strategy to Control the Fluorescence of Acylhydrazone-Based Conjugated Microporous Polymers and Their Application to Nitroaromatics Detection

Acylhydrazone-based fluorescent conjugated microporous polymers (CMPs) with inter-and intra-hydrogen bonding-controlled emissive properties were prepared. The synthesized CMPs (BH-CMP and ABH-CMP) were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, solid-state 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and photoluminescence spectroscopy. Interestingly, BH-CMP exhibited emission enhancement via adsorption of water molecules, whereas the emission of ABH-CMP, which possesses free amine groups, decreased upon the addition of water molecules. The differences in the emission trends of BH-CMP and ABH-CMP in the presence of water molecules originate from the formation of different hydrogen-bonding networks in each CMP. The acylhydrazone-based CMPs were applied to the detection of nitroaromatic compounds. As a result, ABH-CMP in DMF exhibited high selectivity for 1,3,5-trinitrotoluene (TNT) over other nitroaromatic compounds nitrobenzene, 1-chloro-4-nitrobenzene, 2,3-dichloronitrobenzene, and 2,4-dinitrotoluene.

Insights into Biodegradable Polymer-Supported Titanium Dioxide Photocatalysts for Environmental Remediation

During the past two decades, immobilization of titanium dioxide (TiO2), a well-known photocatalyst, on several polymeric substrates has extensively gained ground since it limits the need of post-treatment separation stages. Taking into account the numerous substrates tested for supporting TiO2 photocatalysts, the use of biodegradable polymer seems a hopeful option owing to its considerable merits, including the flexible nature, low price, chemical inertness, mechanical stability and wide feasibility. The present review places its emphasis on recently published research articles (2011–2021) and exhibits the most innovative studies facilitating the eco-friendly biodegradable polymers to fabricate polymer-based photocatalysts, while the preparation details, photocatalytic performance and reuse of the TiO2/polymer photocatalysts is also debated. The biodegradable polymers examined herein comprise of chitosan (CS), cellulose, alginate, starch, poly(lactid acid) (PLA), polycaprolactone (PCL) and poly(lactide-co-glycolide) (PLGA), while an emphasis on the synthetical pathway (dip-coating, electrospinning, etc.) of the photocatalysts is provided.

Poly(2-oxazoline)-Based Amphiphilic Gradient Copolymers as Nanocarriers for Losartan: Insights into Drug–Polymer Interactions

The current study is focused on the development of highly stable drug nanocarriers by encapsulating losartan potassium (LSR) into an amphiphilic biocompatible poly(2-methyl-2-oxazoline)-grad-poly(2-phenyl-2-oxazoline) (PMeOxz72-grad-PPhOxz28) gradient copolymer (GC). Based on dynamic light scattering (DLS), the PMeOxz72-grad-PPhOxz28 (where the subscripts denote %wt composition of the components) GC formed micelles and aggregates of 13 nm and 96 nm in aqueous milieu. The presence of hydrophobic LSR molecules altered the structural characteristics of the GC, modulating the organization of the polymeric components and revealing the formation of hyper micellar nanostructures in addition to micelles. The 2D-NOESY experiments evidenced intermolecular interactions between the phenyl ring of LSR with the phenyl group of PPhOxz and eminent correlations between the butyl chain of LSR with the phenyl group of PPhOxz and methylene group of PMeOxz, respectively. Additionally, NMR studies as a function of temperature demonstrated that the presence of hydrophilic PMeOxz segments in the gradient core of PMeOxz72-grad-PPhOxz28 nanoassemblies induced an increased fluidity of the core matrix, especially upon heating, thus causing water penetration, resulting in increased proton mobility. Lastly, the ultrasound release profile of LSR signified that a great amount of the encapsulated LSR is tightly bound to the PMeOxz72-grad-PPhOxz28 nanoassemblies.

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Current Research on Polyelectrolyte Nanostructures: From Molecular Interactions to Biomedical Applications

Polyelectrolytes have been at the center of interdisciplinary research for many decades. In the field of polymer science and soft matter, they have provided the dimensions of electrostatic interactions, which opens a vast variety of opportunities for new physical properties and applications. In biological matter, polyelectrolytes are present in many forms, from extracellular polysaccharides to complex DNA molecules and proteins. This review discusses the recent research on polyelectrolytes covering the fundamental level of their conformations and nanostructures, their molecular interactions with materials that have close relevance to bioapplications and their applications in the biomedical field. This approach is motivated by the fact that the polyelectrolyte research is constantly active in all the aforementioned levels and continually affects many critical scientific areas.