3D-printed PLA/PEO blend as biodegradable substrate coating with CoCl2 for colorimetric humidity detection

This study aimed to fabricate biodegradable substrate with colorimetric humidity indicator for detective moisture in food packaging. The poor properties of poly(lactic acid) (PLA) were enhanced by melt blending PLA with non-toxic poly(ethylene oxide) PEO at 180 °C. Specifically, three-dimensional (3D) substrates of PLA/PEO blends were fabricated by solvent-cast 3D printing. Furthermore, cobalt chloride (CoCl2) solution was printed onto the substrate with an inkjet printer to serve as a colorimetric humidity sensing indicator. It found that the flexibility and thermal stability of the PLA were improved and the hydrophilicity was increased with an increase in PEO content. Color changes and the sensitivity of this material were confirmed using image analysis and total color difference. The CoCl2 indicator displayed color changes that ranged from blue to pink under ambient conditions (above 60%RH), revealing suitable potential for frozen food packaging material with aim to detect amount of moisture in the packaging

Thermo-Mechanical Properties of Stretchable Nanocomposites Based on Honeycomb Networks of Carbon Nanotubes.

Waterborne polymer colloidal particles (i.e. latex) have been used as a template to fabricate carbon nanotube (CNT) composites. Plasticized colloidal crystals are able to assemble CNTs into ordered hexagonal, or honeycomb-like, networks with periodicity defined by the size and deformability of the polymer latex spheres used to form the nanocomposite. In this work, two-dimensional hexagonal networks have been formed by spin-coating the latex nanocomposite dispersion onto a substrate. The resulting monolayer composites have very interesting thermal expansion behaviour. Due to the significantly lower thermal expansion (CTE) of single-walled CNTs (SWNTs) compared to polymers, nanotube networks act as static belts surrounding latex particles in the thin film plane. The matrix with considerably higher CTE is, therefore, restricted to expand in the film plane. The polymer particles, consequently, expand in the out-of-plane direction, thus displaying a higher CTE in that direction. Ultimately the monolayer films may find application as nanoscale thermal actuators. By using latex matrices with low and high glass transition temperature values, random and ordered honeycomb-like CNT networks can be formed in bulk composite samples, respectively. The ability to control CNT network formation results in a variation of thermal conductivity (K) of the nanocomposites. Compared to the composite with random CNT networks, a K enhancement has been found when ordered segregated nanotube networks are created, especially in the case of SWNT composites that offer higher K than the case of composites consisting of multi-walled CNTs. In addition, the thermal percolation threshold has been found to be markedly low due to large excluded volume of the polymer matrix in ordered networks of SWNTs. After spin-coating particle monolayers of CNT-latex blends onto a polymer substrate, the mechanics of the unusual monolayer elasticity has been investigated. Polarized Raman spectroscopy reveals a uniform alignment of the nanotube networks in the strained monolayers. Systematic changes in the resulting Raman spectra of the monolayer under strain indicate that stress is transferred from the colloidal matrix to SWNT inclusions as observed from the Raman G’-band shift. These are explained by strain and slippage of individual SWNTs in the bundles. Additionally, elastic recovery of the monolayer has been found after being strained beyond failure, which may be related to the inter-tube van der Waals forces pulling individual tubes back to their bundles and, therefore, latex particles back to original morphology

Thermo-Mechanical Properties of Stretchable Nanocomposites Based on Honeycomb Networks of Carbon Nanotubes.

Waterborne polymer colloidal particles (i.e. latex) have been used as a template to fabricate carbon nanotube (CNT) composites. Plasticized colloidal crystals are able to assemble CNTs into ordered hexagonal, or honeycomb-like, networks with periodicity defined by the size and deformability of the polymer latex spheres used to form the nanocomposite. In this work, two-dimensional hexagonal networks have been formed by spin-coating the latex nanocomposite dispersion onto a substrate. The resulting monolayer composites have very interesting thermal expansion behaviour. Due to the significantly lower thermal expansion (CTE) of single-walled CNTs (SWNTs) compared to polymers, nanotube networks act as static belts surrounding latex particles in the thin film plane. The matrix with considerably higher CTE is, therefore, restricted to expand in the film plane. The polymer particles, consequently, expand in the out-of-plane direction, thus displaying a higher CTE in that direction. Ultimately the monolayer films may find application as nanoscale thermal actuators. By using latex matrices with low and high glass transition temperature values, random and ordered honeycomb-like CNT networks can be formed in bulk composite samples, respectively. The ability to control CNT network formation results in a variation of thermal conductivity (K) of the nanocomposites. Compared to the composite with random CNT networks, a K enhancement has been found when ordered segregated nanotube networks are created, especially in the case of SWNT composites that offer higher K than the case of composites consisting of multi-walled CNTs. In addition, the thermal percolation threshold has been found to be markedly low due to large excluded volume of the polymer matrix in ordered networks of SWNTs. After spin-coating particle monolayers of CNT-latex blends onto a polymer substrate, the mechanics of the unusual monolayer elasticity has been investigated. Polarized Raman spectroscopy reveals a uniform alignment of the nanotube networks in the strained monolayers. Systematic changes in the resulting Raman spectra of the monolayer under strain indicate that stress is transferred from the colloidal matrix to SWNT inclusions as observed from the Raman G’-band shift. These are explained by strain and slippage of individual SWNTs in the bundles. Additionally, elastic recovery of the monolayer has been found after being strained beyond failure, which may be related to the inter-tube van der Waals forces pulling individual tubes back to their bundles and, therefore, latex particles back to original morphology

Toughening Polylactide Stereocomplex by Injection Molding with Thermoplastic Starch and Chain Extender

The high cost, low heat resistance, and brittleness of poly(L-lactide) (PLLA) is a significant drawback that inhibits its diffusion into many industrial applications. These weaknesses were solved by forming a polylactide stereocomplex (ST) and blending it with thermoplastic starch (TPS). We blended poly (L-lactide)(PLLA), up to 30% thermoplastic starch, and a chain extender (2%) in an internal mixer, which was then hand-mixed with poly (D-lactide)(PDLA) and injection molded to form specimens, in order to study mechanical, thermal, and crystallization behavior. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (XRD) demonstrated that the stereocomplex structures were still formed despite the added TPS and showed melting points ~55 °C higher than neat PLLA. Furthermore, stereocomplex crystallinity decreased with the increased TPS content. Dynamic mechanical analysis revealed that ST improved PLLA heat resistance, and tensile testing suggested that the TPS improved the elongation-at-break of ST. Moreover, the chain extender reduced the degradation of ST/TPS blends and generally improved ST/TPS composites’ mechanical properties

Enhancement of Poly(vinyl alcohol) Hydrogel Properties by N-Succinyl Chitosan and Mesona chinensis Extract for Use as Wound Dressings

Hydrogels composed of different ratios of poly(vinyl alcohol), N-succinyl chitosan (NSC), and Mesona chinensis extract, for use as a wound dressing, were synthesized via thermal polymerization. Potassium persulfate was chosen as the initiator and glutaraldehyde as the crosslinking agent. NSC was prepared by modification of chitosan with succinic anhydride. It was found that this preparation method gave a high gel fraction percentage. The structures of the prepared hydrogels were characterized by Fourier-transform infrared spectroscopy, and their morphology by scanning electron microscopy (SEM). In addition, water transport properties, mechanical properties and cytotoxicity were also studied. The SEM results show that the hydrogels exhibited porous structures and that pore size and size distribution increased with increasing NSC content. Hydrogel-water interactions and water transport properties were also studied in terms of swelling ratio, equilibrium water retention, and water vapour transmission rate. These showed an increase, from 637 to 1240 %, 17.8 to 21.4 %, and 110 to 121 g h−1 m−2 respectively with an increase in NSC content. These gels exhibit a lower water vapour transmission rate compared to that of second and third degree burns but higher than normal skin. Similarly, NSC improved the mechanical properties, presented in terms of stress and percentage strain, of the hydrogels. The stress, percentage strain, and Young’s modulus were found to increase from 15 to 32 kPa, 197 to 294 %, and 0.078 to 0.133 kPa respectively. The hydrogels can be considered to be non-toxic based on the in vitro cytotoxicity assay results. In conclusion, the results showed that, by varying composition, hydrogel properties can be tuned to the specific requirements of an ideal wound dressing

HPMC/PVP K90 Dissolving Microneedles Fabricated from 3D-Printed Master Molds: Impact on Microneedle Morphology, Mechanical Strength, and Topical Dissolving Property

Three-dimensional (3D) printing can be used to fabricate custom microneedle (MN) patches instead of the conventional method. In this work, 3D-printed MN patches were utilized to fabricate a MN mold, and the mold was used to prepare dissolving MNs for topical lidocaine HCl (L) delivery through the skin. Topical creams usually take 1–2 h to induce an anesthetic effect, so the delivery of lidocaine HCl from dissolving MNs can allow for a therapeutic effect to be reached faster than with a topical cream. The dissolving-MN-patch-incorporated lidocaine HCl was constructed from hydroxypropyl methylcellulose (HPMC; H) and polyvinyl pyrrolidone (PVP K90; P) using centrifugation. Additionally, the morphology, mechanical property, skin insertion, dissolving behavior, drug-loading content, drug release of MNs and the chemical interactions among the compositions were also examined. H51P2-L, H501P2-L, and H901P2-L showed an acceptable needle appearance without bent tips or a broken structure, and they had a low % height change (80%). These three formulations exhibited a drug-loading content approaching 100%. Importantly, the composition-dependent dissolving abilities of MNs were revealed. Containing the lowest amount of HPMC in its formulation, H901P2-L showed the fastest dissolving ability, which was related to the high amount of lidocaine HCl released through the skin. Moreover, the results of an FTIR analysis showed no chemical interactions among the two polymers and lidocaine HCl. As a result, HPMC/PVP K90 dissolving microneedles can be used to deliver lidocaine HCl through the skin, resulting in a faster onset of anesthetic action

Preparation and Characterization of PLG Microparticles by the Multiple Emulsion Method for the Sustained Release of Proteins

Rapid release and diminished stability are two of the limitations associated with the growth factors that are essentially used in dental applications. These growth factors are employed to enhance the quality and quantity of tissue or bone matter during regeneration. Therefore, drug delivery devices and systems have been developed to address these limitations. In this study, bovine serum albumin (BSA), as a representative growth factor, was successfully sustained by encapsulation with the medium-absorbable copolymer, poly(L-lactide-co-glycolide) (PLG) 70:30% mol, via the multiple emulsion method. Different PLG, PVA, and BSA concentrations were used to investigate their effects on the BSA encapsulation efficiency. The suitable ratios leading to a better characterization of microparticles and a higher encapsulation efficiency in producing encapsulated PLG microparticles were 8% (w/v) of PLG, 0.25% (w/v) of PVA, and 8% (w/v) of BSA. Furthermore, an in vitro release study revealed a bursting release of BSA from the encapsulated PLG microsphere in the early phase of development. Subsequently, a gradual release was observed over a period of eight weeks. Furthermore, to encapsulate LL-37, different proteins were used in conjunction with PLG under identical conditions with regard to the loading efficiency and morphology, thereby indicating high variations and poor reproducibility. In conclusion, the encapsulated PLG microparticles could effectively protect the protein during encapsulation and could facilitate sustainable protein release over a period of 60 days. Importantly, an optimal method must be employed in order to achieve a high degree of encapsulation efficiency for all of the protein or growth factors. Accordingly, the outcomes of this study will be useful in the manufacture of drug delivery devices that require medium-sustained release growth factors, particularly in dental treatments

Low cytotoxicity, antibacterial property, and curcumin delivery performance of toughness-enhanced electrospun composite membranes based on poly(lactic acid) and MAX phase (Ti3AlC2)

MXenes, synthesized from their precursor MAX phases, have been extensively researched as additives to enhance the drug delivery performance of polymer matrices, whereas there is a limited number of previous reports on the use of MAX phases themselves for such applications. The use of MAX phases can exclude the complicated synthesis procedure and lessen resultant production and environmental costs required to convert MAX phases to MXenes. Herein, electrospun membranes of poly(lactic acid) (PLA) and a MAX phase (Ti3AlC2) have been fabricated for curcumin delivery. The composite membrane exhibits significantly higher toughness (8.82 MJ m-3) than the plasticized PLA membrane (0.63 MJ m-3) with low cytotoxicity, supporting proliferation of mouse fibroblast L929 cells. The curcumin-loaded composite membrane exhibits high water vapor transmission (~7350 g m-2 day-1), porosity (~85 %), water wettability, and antibacterial properties against E. coli and S. aureus. Seven-day curcumin release is enhanced from 45 % (PLA) to 67 % (composite) due to curcumin diffusion from the polymer fibers and MAX phase surface that contributes to overall increased curcumin adsorption and release sites. This work demonstrates the potential of the MAX phase to enhance both properties and curcumin delivery, promising for other eco-friendly systems for sustainable drug delivery applications

Reactive Blending of Modified Thermoplastic Starch Chlorhexidine Gluconate and Poly(butylene succinate) Blending with Epoxy Compatibilizer

Biodegradable starch-based polymers were developed by melt-blending modified thermoplastic starch (MTPS) with poly(butylene succinate) (PBS) blended with epoxy resin (Er). A modified thermoplastic starch blend with chlorhexidine gluconate (MTPSCh) was prepared by melt-blending cassava starch with glycerol and chlorhexidine gluconate (CHG) 1.0% wt. The Er was melt-blended with PBS (PBSE) at concentrations of 0.50%, 1.0%, 2.5%, and 5.0% (wt%/wt%). The mechanical properties, water resistance, and morphology of the MTPSCh/PBSE blends were investigated. The MTPSCh/PBSE2.5% blend showed an improvement in tensile strength (8.1 MPa) and elongation at break (86%) compared to the TPSCh/PBS blend (2.6 MPa and 53%, respectively). In addition, water contact angle measurements indicated an increase in the hydrophobicity of the MTPSCh/PBSE blends. Thermogravimetric analysis showed an improvement in thermal stability when PBS was added to the MTPSCh blends. Fourier transform infrared spectroscopy data confirmed a new reaction between the amino groups of CHG in MTPSCh and the epoxy groups of Er in PBSE, which improved the interfacial adhesion of the MTPSCh/PBSE blends. This reaction improved the mechanical properties, water resistance, morphology, and thermal stability of the TPSCh/PBSE blends