Nanosize and microsize clay effects on the kinetics of the thermal degradation of polylactides

Organomodified nanoclay with boron compounds is improving structural and antibacterial properties of nanofibrous matrices

In this study, nanofibrous polymeric matrices were successfully developed with nanoclay, montmorillonite (MMT) and various boron (B) compounds, which were known to have positive effects on the wound healing with elevated antibacterial properties. For this purpose, MMT was modified with quaternary ammonium salt, trimethyl octadecyl ammonium bromide (TMOD), and boron compounds, boron nitride (BN), zinc borate (ZB), or phenylboronic acid (PBA) were adsorbed on organomodified MMT (OMMT). Then, poly (lactic acid) (PLA) based nanofibrous PLA-OMMT/B composites were fabricated via electrospinning. Modification of MMT nanoparticles with TMOD occurred through ion-exchange reaction and led to better homogenous fibrous structures which exhibited dramatic inhibition for gram-positive bacteria. Moreover, composites with ZB and PBA demonstrated both bacteriostatic and bactericidal effects for gram-positive and gram-negative bacteria. The chemical structures of the matrices were evaluated through ATR-FTIR and supported the intercalated composite formation. The thermal and mechanical stabilities of PLA matrices were also enhanced after OMMT and B incorporation. The lowest breaking strain value was recorded for PLA-OMMT/PBA composite compared to other B composites. The 100% and 50% extracts of the PLA-OMMT matrices showed modest cytotoxic effect on the human dermal fibroblasts (NHDF) on the second day culture that probably originated from TMOD. These results demonstrated that PLA-OMMT/B matrices, especially PBA including matrices, can be used as replaceable wound dressings that have limited interaction with cells but exhibit antibacterial activity and support the early stages of wound healing both morphologically and chemically.

Combined Effects from Dual Incorporation of ATBC as Plasticizer and Mesoporous MCM-41 as Nucleating Agent on the PLA Isothermal Crystallization in Environmentally-Friendly Ternary Composite Systems

Different materials, based on an L-rich polylactide (PLA) as matrix, acetyl tri-n-butyl citrate (ATBC) as plasticizer, and mesoporous Mobile Crystalline Material.41 (MCM-41) particles as nucleating agent, were attained by melt extrusion. These materials are constituted by (a) binary blends of PLA and ATBC with different contents of the latest; (b) a dual compound of PLA and a given amount of MCM-41 silica (5 wt.%); and (c) ternary composites that include PLA, ATBC at several compositions and mesoporous MCM-41 at 5 wt.%. Influence of the incorporation of the plasticizer and nucleating particles has been comprehensively analyzed on the different phase transitions: glass transition, cold crystallization, melt crystallization and melting processes. Presence of both additives moves down the temperature at which PLA phase transitions take place, while allowing the PLA crystallization from the melt at 10 °C/min in the composites. This tridimensional ordering is not noticeable in the pristine PLA matrix and, accordingly, PLA crystallization rate is considerably increased under dynamic conditions and also after isothermal crystallization from either the melt or the glassy state. An important synergistic effect of dual action of ATBC and MCM-41 has been, therefore, found.

High-Pressure Depolymerization of Poly(lactic acid) (PLA) and Poly(3-hydroxybutyrate) (PHB) Using Bio-Based Solvents: A Way to Produce Alkyl Esters Which Can Be Modified to Polymerizable Monomers

The polyesters poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) used in various applications such as food packaging or 3D printing were depolymerized by biobased aliphatic alcohols-methanol and ethanol with the presence of para-toluenesulphonic acid (p-TSA) as a catalyst at a temperature of 151 °C. It was found that the fastest depolymerization is reached using methanol as anucleophile for the reaction with PLA, resulting in the value of reaction rate constant (k) of 0.0425 min^-1 and the yield of methyl lactate of 93.8% after 120 min. On the other hand, the value of constant k for the depolymerization of PHB in the presence of ethanol reached 0.0064 min^-1 and the yield of ethyl 3-hydroxybutyrate was of 76.0% after 240 min. A kinetics study of depolymerization was performed via LC-MS analysis of alkyl esters of lactic acid and 3-hydroxybutanoic acid. The structure confirmation of the products was performed via FT-IR, MS, ¹H NMR, and ¹³C NMR. Synthesized alkyl lactates and 3-hydroxybutyrates were modified into polymerizable molecules using methacrylic anhydride as a reactant and potassium 2-ethylhexanoate as a catalyst at a temperature of 80 °C. All alkyl esters were methacrylated for 24 h, guaranteeing the quantitative yield (which in all cases reached values equal to or of more than 98%). The methacrylation rate constants (k') were calculated to compare the reaction kinetics of each alkyl ester. It was found that lactates reach afaster rate of reaction than 3-hydroxybutyrates. The value of k' for themethacrylated methyl lactate reached 0.0885 dm³/(mol·min). Opposite to this result, methacrylated ethyl 3-hydroxybutyrate's constant k' was 0.0075 dm³/(mol·min). The reaction rate study was conducted by the GC-FID method and the structures were confirmed via FT-IR, MS, ¹H NMR, and ¹³C NMR.

Processing Compostable PLA/Organoclay Bionanocomposite Foams by Supercritical CO2 Foaming for Sustainable Food Packaging

This article proposes a foaming method using supercritical carbon dioxide (scCO2) to obtain compostable bionanocomposite foams based on PLA and organoclay (C30B) where this bionanocomposite was fabricated by a previous hot melt extrusion step. Neat PLA films and PLA/C30B films (1, 2, and 3 wt.%) were obtained by using a melt extrusion process followed by a film forming process obtaining films with thicknesses between 500 and 600 μm. Films were further processed into foams in a high-pressure cell with scCO2 under constant conditions of pressure (25 MPa) and temperature (130 °C) for 30 min. Bionanocomposite PLA foams evidenced a closed cell and uniform cell structure; however, neat PLA presented a poor cell structure and thick cell walls. The thermal stability was significantly enhanced in the bionanocomposite foam samples by the good dispersion of nanoclays due to scCO2, as demonstrated by X-ray diffraction analysis. The bionanocomposite foams showed improved overall mechanical performance due to well-dispersed nanoclays promoting increased interfacial adhesion with the polymeric matrix. The water uptake behavior of bionanocomposite foams showed that they practically did not absorb water during the first week of immersion in water. Finally, PLA foams were disintegrated under standard composting conditions at higher rates than PLA films, showing their sustainable character. Thus, PLA bionanocomposite foams obtained by batch supercritical foaming seem to be a sustainable option to replace non-biodegradable expanded polystyrene, and they represent a promising alternative to be considered in applications such as food packaging and other products.

Bio-based thermoplastic natural rubber based on poly(lactic acid)/thermoplastic starch/calcium carbonate nanocomposites

Bio-based thermoplastic natural rubber (TPNR) has recently received much attention due to its sustainability. TPNR based on natural rubber (NR), poly(lactic acid) (PLA), thermoplastic starch (TPS), and nano-precipitated calcium carbonate (NPCC) was fabricated using a twin-screw extruder with two different mixing sequences: MI (NPCC was first compounded with PLA) and MII (NPCC was initially compounded with TPS), and then converted to a sheet through cast sheet extrusion. A constant weight ratio of NR:PLA:TPS at 30:40:30 and varying concentrations of NPCC at 0.5, 1, 3, and 5 wt% were employed. The effects of NPCC and mixing sequence on the properties of NR/PLA/TPS/NPCC nanocomposites were investigated. The NR and TPS phases were dispersed in the PLA matrix. The nanocomposites loaded with a small amount of NPCC (0.5 and 1 wt%) showed increased tensile strength and Young's modulus. NPCC enhanced melt flowability, slightly improved the water vapor barrier property of the NR/PLA/TPS blend and caused decreased T_g, T_cc, and T_m of PLA in the nanocomposites. The PLA phase of the MI nanocomposites contained a higher amount of NPCC, consequently having greater PLA chain scission and poorer tensile properties than that of the MII nanocomposites.

Characterisation and Modelling of PLA Filaments and Evolution with Time

The properties of polylactic acid (PLA) filaments have not yet been analysed in detail, and they are strongly affected by the extrusion process used in some additive manufacturing systems. Here we present the mechanical, thermal, physical, and fractographical properties of an extruded filament (not the bulk material or scaffolds), the basic building block of any PLA structure printed via material extrusion. This research aims to create a reference point for the modelisation of additively manufactured structures via extrusion processes, as the main building block is characterised in detail for a deep understanding. Furthermore, we investigated the natural ageing (up to one year), the effect of the printing (extruding) temperature (180 and 190 °C), and the effect of the crosshead speed during the tensile tests (10⁻¹ to 10² mm/min) to provide a deeper analysis of the material. The results showed that the material extruded at 190 °C performed better than the material extruded at 180 °C. However, after one hundred days of natural ageing, both materials behaved similarly. This was related to the flow-induced molecular orientation during the extrusion. The crosshead rate produced a logarithmic increase of the mechanical properties, consistent with the Eyring model. Additionally, the ageing produced significant changes in both the elastic modulus and the yield strength: from 2.4 GPa and 40 MPa, in one-day-aged samples, up to 4 GPa and 62 MPa once entirely aged. Finally, it was observed that the glass transition and the enthalpic relaxation increased with ageing, agreeing with the Kohlraushch–William–Watts model.

Polylactic acid/Gemini surfactant modified clay bio-nanocomposites: Morphological, thermal, mechanical and barrier properties

To improve PLA's properties and overcome its drawbacks such us poor thermal stability, resistance and gas barrier properties, several studies have been performed using different nanofillers. In this work, PLA nanocomposites reinforced by three organoclays, OMt(8-4-8), OMt(10-4-10) and OMt(12-4-12) at various weight percentages (1 and 3 wt%) were prepared by melt mixing using a twin-screw extruder. The organoclays were obtained from sodium montmorillionite and gemini surfactants bearing different hydrophobic chain lengths. The resulting nanocomposites have been characterized in terms of composition and morphology by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal stability and cold crystallization behavior were accessed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of clay composition and concentration on the mechanical and rheological properties of the nanocomposites as well as their water vapor permeability has been also investigated. The resulting nanocomposites exhibit a significantly reduced permeability as compared to unfilled PLA and an improved young modulus and toughness at the detriment of ductility.

The biopolymer ulvan from Ulva fasciata: Extraction towards nanofibers fabrication

As a biocompatible polymer, ulvan has applications in countless fields. Therefore, the following study intends to extract ulvan from Ulva fasciata, emphasizing its use for biomedical and industrial applications in the manufacture of nanofibrous webs. The extracted ulvan was characterized using FT-IR, DSC, XRD, GPC, and NMR. The extracted ulvan's FT-IR spectra confirmed that it is a sulfated polysaccharide. The HPLC analysis showed that the extracted ulvan is composed of rhamnose, xylose, glucose and glucuronic acid. NMR showed that the proton chemical shifts at 1.3 are due to methyl protons of rhamnose 3-sulfate in the ulvan samples. The X-ray diffractograms suggested that the extracted ulvan is semi-crystalline polymer with major crystalline reflection at 2θ of 29.4°. Deionized water has been successfully used to produce ulvan/polyvinyl alcohol (ulvan/PVA) nanofibers as an eco-friendly solvent. It was found that the ulvan-to-PVA (1:2) ratio results in nanofiber that is well handled and smooth. In addition to pretreated ones, the ulvan extracted without organic solvent pretreatment showed bead free nanofibers. It is concluded that pretreatment with organic solvent in ulvan extraction, particularly in the manufacture of nanofibers, is not recommended. In addition, the resulting nanofibrous mat has sufficient mechanical properties for various applications to be incorporated.

Kinetic Study of Depolymerization of Lactic and Glycolic Acid Oligomers in the Presence of Oxide Catalysts

For glycolic acid oligomers (GAO): l-lactic acid oligomers (LAO) mixtures, as an example, it was shown that the nature of the active sites of the catalysts significantly affect the depolymerization process. So, ZnO, which has mainly basic sites, leads to the highest yield of cyclic diesters. On the contrary, depolymerization in the presence of acidic γ-Al₂O₃ and without a catalyst is characterized by lower diester yields due to the prevalence of a side polycondensation reaction. Using GAO:LAO mixtures, it was shown that in the case of three studied systems (with ZnO, γ-Al₂O₃, and without catalyst), mixed interactions occurred, including homo-paired and hetero-paired intermolecular interactions, as well as intramolecular interactions of oligomeric molecules. Kinetic models of the processes under study were determined by isoconversional thermal analysis. In the case of depolymerization of oligomers in the presence of ZnO, the kinetic model was between the kinetic models of the first (F1) and second (F2) orders, while in depolymerization in the presence of γ-Al₂O₃ and without a catalyst, the process was described by diffusion models such as the Jander equation (D3) and Zhuravlev, Lesokin, Tempelman equation (D5).

Targeting Delivery System for Lactobacillus Plantarum Based on Functionalized Electrospun Nanofibers

With the increased interest in information on gut microbes, people are realizing the benefits of probiotics to health, and new technologies to improve the viability of probiotics are still explored. However, most probiotics have poor resistance to adverse environments. In order to improve the viability of lactic acid bacteria, polylactic acid (PLA) nanofibers were prepared by coaxial electrospinning. The electrospinning voltage was 16 kV, and the distance between spinneret and collector was 15 cm. The feed rates of the shell and core solutions were 1.0 and 0.25 mL/h, respectively. The lactic acid bacteria were encapsulated in the coaxial electrospun nanofibers with PLA and fructooligosaccharides (FOS) as the shell materials. Scanning electron microscopy, transmission electron microscopy, and laser scanning confocal microscopy showed that lactic acid bacteria were encapsulated in the coaxial electrospun nanofibers successfully. The water contact angle test indicated that coaxial electrospun nanofiber films had good hydrophobicity. An in vitro simulated digestion test exhibited that the survival rate of lactic acid bacteria encapsulated in coaxial electrospun nanofiber films was more than 72%. This study proved that the viability of probiotics can be improved through encapsulation within coaxial electrospun PLA nanofibers and provided a novel approach for encapsulating bioactive substances.

Thermal and thermo-oxidative degradation kinetics and characteristics of poly (lactic acid) and its composites

Thermal degradation behavior and kinetics of starch/PLA composites in an inert and oxygen atmosphere were investigated by TG and TG-FTIR techniques. It is shown that the thermal degradation process can be divided into three stages, and a significant difference between thermal and thermo-oxidative degradation is the third stage in which the residual chars are further cracked for the thermo-oxidative degradation. The activation energy was calculated using the iso-conversional Flynn-Wall-Ozawa (FWO) method. The lower activation energy for thermo-oxidative degradation indicated that oxygen had an accelerated effect on thermal degradation. The variation of activation energy indicated that the decomposition of all the samples was a complex process that included at least two different mechanisms. Evolution of the evolved gaseous products with temperature was studied to understand the thermal and thermo-oxidative decomposition comprehensively. According to the TG-FTIR analysis, the gaseous products mainly contained lactide, cyclic oligomers, aldehydes, CO₂, CO, and H₂O.

Understanding thermal decomposition kinetics of flame-retardant thermoset polylactic acid

The Flynn–Wall–Ozawa method was applied to study the local activation energy of flame retardant thermoset PLA, and the results showed that with an increase of conversion of thermal degradation, the local activation energy was increased slowly. When the conversion of thermal degradation was under 15%, the activation energy of flame retardant thermoset PLA was lower than that of thermoset PLA, attributed to the low bond energy of P–C bond. When the conversion of thermal degradation exceeded 15%, the dehydration charcoal effect of phosphorous compound slowed down the process of thermal degradation, and the activation energy of flame retardant thermoset PLA was higher than that of thermoset PLA, indicating that the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) enhances the thermal stability of thermoset PLA. The Coats–Redfern method and invariant kinetic parameters method were used to understand kinetics details about this process including the activation energy and apparent pre-exponential factor, and estimated contribution ratios for the 18 kinetic functions. The results showed that the addition of DOPO didn't impact the most important mechanism of thermal degradation but changed the contribution ratios of the 18 kinetic functions. According to the functional relationship between decomposition rate with temperature and quality conversion rate, three-dimension surface plots were made to understand the change regulation of decomposition rate. We found that the addition of DOPO reduced the decomposition rate of thermoset PLA, attributing to the dehydration charcoal effect of phosphorous compound which restrained the interesterification of PLA, and thus enhancing the thermal stability of thermoset PLA.

The Flynn–Wall–Ozawa method was applied to study the local activation energy of flame retardant thermoset PLA, and the results showed that with an increase of conversion of thermal degradation, the local activation energy was increased slowly.

The Effect of Substances of Plant Origin on the Thermal and Thermo-Oxidative Ageing of Aliphatic Polyesters (PLA, PHA)

The stabilization efficiency of flavonoids (rutin and hesperidin) in polyester (polylactide (PLA) and polyhydroxyalkaonate (PHA)) composites under oxygen at high temperature was investigated. The polymer was homogenized with three antioxidants then processed by extrusion. The effects of stabilizers on the following physicochemical properties were investigated: melt flow, Vicat softening temperature, surface energy, and color change (Cie-Lab space). The aim of this study was to improve the stability of aliphatic polyesters by extending and controlling their lifetime. Differential Scanning Calorimetry DSC and Thermogravimetric analysis DTG methods were used to confirm the stabilizing effects (the inhibition of oxidation) of flavonoids (rutin and hesperidin) on the ageing process of biodegradable polymers. The levels of migration of plant antioxidants from PLA and PHA were determined and compared to the industrial stabilizer (Chimassorb 944 UV absorber). Based on this study, a comparable-to-higher efficiency of the proposed flavonoids for the stabilization of polyesters was found when compared to the commercial stabilizers. Thus, in the future, natural plant-derived substances may replace toxic hindered amines, which are commonly used as light stabilizers (HALS-Hindered Amine Light Stabilizers) in the polymer industry.

PLA Melt Stabilization by High-Surface-Area Graphite and Carbon Black

Small amounts of carbon nanofillers, specifically high-surface-area graphite (HSAG) and more effectively carbon black (CB), are able to solve the well-known problem of degradation (molecular weight reduction) during melt processing, for the most relevant biodegradable polymer, namely poly(lactic acid), PLA. This behavior is shown by rheological measurements (melt viscosity during extrusion experiments and time sweep-complex viscosity) combined with gel permeation chromatography (GPC) experiments. PLA's molecular weight, which is heavily reduced during melt extrusion of the neat polymer, can remain essentially unaltered by simple compounding with only 0.1 wt % of CB. At temperatures close to polymer melting by compounding with graphitic fillers, the observed stabilization of PLA melt could be rationalized by scavenging traces of water, which reduces hydrolysis of polyester bonds. Thermogravimetric analyses (TGA) indicate that the same carbon fillers, on the contrary, slightly destabilize PLA toward decomposition reactions, leading to the loss of volatile byproducts, which occur at temperatures higher than 300 °C, i.e., far from melt processing conditions.

Triethyl Citrate (TEC) as a Dispersing Aid in Polylactic Acid/Chitin Nanocomposites Prepared via Liquid-Assisted Extrusion

The production of fully bio-based and biodegradable nanocomposites has gained attention during recent years due to environmental reasons; however, the production of these nanocomposites on the large-scale is challenging. Polylactic acid/chitin nanocrystal (PLA/ChNC) nanocomposites with triethyl citrate (TEC) at varied concentrations (2.5, 5.0, and 7.5 wt %) were prepared using liquid-assisted extrusion. The goal was to find the minimum amount of the TEC plasticizer needed to enhance the ChNC dispersion. The microscopy study showed that the dispersion and distribution of the ChNC into PLA improved with the increasing TEC content. Hence, the nanocomposite with the highest plasticizer content (7.5 wt %) showed the highest optical transparency and improved thermal and mechanical properties compared with its counterpart without the ChNC. Gel permeation chromatography confirmed that the water and ethanol used during the extrusion did not degrade PLA. Further, Fourier transform infrared spectroscopy showed improved interaction between PLA and ChNC through hydrogen bonding when TEC was added. All results confirmed that the plasticizer plays an important role as a dispersing aid in the processing of PLA/ChNC nanocomposites.

Physical and mechanical properties of PLA, and their functions in widespread applications - A comprehensive review

Poly(lactic acid) (PLA), so far, is the most extensively researched and utilized biodegradable aliphatic polyester in human history. Due to its merits, PLA is a leading biomaterial for numerous applications in medicine as well as in industry replacing conventional petrochemical-based polymers. The main purpose of this review is to elaborate the mechanical and physical properties that affect its stability, processability, degradation, PLA-other polymers immiscibility, aging and recyclability, and therefore its potential suitability to fulfill specific application requirements. This review also summarizes variations in these properties during PLA processing (i.e. thermal degradation and recyclability), biodegradation, packaging and sterilization, and aging (i.e. weathering and hygrothermal). In addition, we discuss up-to-date strategies for PLA properties improvements including components and plasticizer blending, nucleation agent addition, and PLA modifications and nanoformulations. Incorporating better understanding of the role of these properties with available improvement strategies is the key for successful utilization of PLA and its copolymers/composites/blends to maximize their fit with worldwide application needs.

Biodegradable ceramic-polymer composites for biomedical applications: A review

The present work focuses on the state-of-the-art of biodegradable ceramic-polymer composites with particular emphasis on influence of various types of ceramic fillers on properties of the composites. First, the general needs to create composite materials for medical applications are briefly introduced. Second, various types of polymeric materials used as matrices of ceramic-containing composites and their properties are reviewed. Third, silica nanocomposites and their material as well as biological characteristics are presented. Fourth, different types of glass fillers including silicate, borate and phosphate glasses and their effect on a number of properties of the composites are described. Fifth, wollastonite as a composite modifier and its effect on composite characteristics are discussed. Sixth, composites containing calcium phosphate ceramics, namely hydroxyapatite, tricalcium phosphate and biphasic calcium phosphate are presented. Finally, general possibilities for control of properties of composite materials are highlighted.

Formulation of benzoxaborole drugs in PLLA: from materials preparation to in vitro release kinetics and cellular assays

A complete investigation on the incorporation of simple benzoxaboroles into PLLA-based films was carried out.

Preparation and characterization of polyurethane-imide/kaolinite nanocomposite foams

A novel PUI/kaolinite nanocomposite foam was prepared byin situpolymerization, and intercalated and exfoliated structures of the modified kaolinite were formed in the PUI foams.

Using water to modify the localization of clay in immiscible polymer blends

The injection of water during melt blending modified the localization of clay in immiscible polymer blends from one phase to the other and improved their dispersion state.

Elaboration of poly(lactic acid)/halloysite nanocomposites by means of water assisted extrusion: structure, mechanical properties and fire performance

This study shows the interest of elaborating polylactide/halloysite nanocomposites by means of water assisted extrusion (WAE). Besides, WAE gives access to materials with improved fire properties and prevents molecular degradation.

Biodegradation assessment of PLA and its nanocomposites

Poly(lactic acid) nanocomposites containing Cloisite 15A, Cloisite 30B, and Dellite 43B were prepared by melt-mixing in a batch mixer and were exposed to UV radiation, temperature, and microorganism in solution and in a compost. Exposed samples, collected along the time, were characterized by several techniques. While the addition of organoclays had a positive effect on thermal stability, the degradation rate of nanocomposites increased when exposed to UV radiation and microorganism. Moreover, the degradation rate depends on the organoclay type. Even though the degradation rate is higher for nanocomposites, Fourier transform infrared spectrometry and gel permeation chromatography results demonstrated that the degradation mechanism is the same.

Improved percutaneous delivery of ketoprofen using combined application of nanocarriers and silicon microneedles

Objectives

The aim of our study was to evaluate the effect of designing ketoprofen-loaded nanosized spheres and combining them with solid silicon microneedles for enhanced and sustained percutaneous drug delivery.

Methods

Ketoprofen-loaded nanoparticles (KET-NP) were designed by modified solvent displacement method, using poly (D, L-lactic acid) (PDLLA). All prepared nanoparticles were characterised with regard to their particle size distribution, morphology, surface properties, thermal behaviour, drug content, drug release and stability. In-vitro skin permeation studies were conducted on Franz-type diffusion cells using porcine skin treated with ImmuPatch silicon microneedles (Tyndall Nation Institute, Cork, Ireland).

Key findings

The study showed that uniform nanospheres were prepared with high encapsulation efficiency and retained stable for 2 months. After an initial burst release, the PDLLA nanoparticles were capable of sustaining and controlling ketoprofen release that followed Korsmeyer–Peppas kinetics. An enhanced flux of ketoprofen was observed in the skin treated with silicon microneedles over a prolonged period of time.

Conclusions

Following application of silicon microneedle arrays, KET-NP were able to enhance ketoprofen flux and supply the porcine skin with drug over a prolonged (24 h) period of time. Our findings indicate that the delivery strategy described here could be used for the further development of effective and painless administration systems for sustained percutaneous delivery of ketoprofen.