Poly L-lactic Acid Surface Research Articles

Catalyst-Free Amino-Yne Click Reaction: An Efficient Way for Immobilizing Amoxicillin onto Polymeric Surfaces.

Surface modifications play a crucial role in enhancing the functionality of biomaterials. Different approaches can be followed in order to achieve the bioconjugation of drugs and biological compounds onto polymer surfaces. In this study, we focused on the immobilization of an amoxicillin antibiotic onto the surface of poly-L-lactic acid (PLLA) using a copper-free amino-yne click reaction. The utilization of this reaction allowed for a selective and efficient bioconjugation of the amoxicillin moiety onto the PLLA surface, avoiding copper-related concerns and ensuring biocompatibility. The process involved sequential steps that included surface activation via alkaline hydrolysis followed by an amidation reaction with ethylendiamine, functionalization with propiolic groups, and subsequent conjugation with amoxicillin via a click chemistry approach. Previous amoxicillin immobilization using tryptophan and fluorescent amino acid conjugation was carried out in order to determine the efficacy of the proposed methodology. Characterization techniques such as X-ray photoelectron spectroscopy (XPS), Attenuated Total Reflection (ATR)-Fourier Transform Infrared (FTIR) spectroscopy, surface imaging, water contact angle determination, and spectroscopic analysis confirmed the successful immobilization of both tryptophan and amoxicillin while maintaining the integrity of the PLLA surface. This tailored modification not only exhibited a novel method for surface functionalization but also opens avenues for developing antimicrobial biomaterials with improved drug-loading capacity.

Enhancement of Poly-L-lactic acid stents through polydopamine coating: Boosting endothelialization and suppressing inflammation

The utilization of Poly-L-lactic acid (PLLA) as a biodegradable material for biovascular scaffolds (BVS) stems from its superior mechanical attributes, biodegradability, and biocompatibility. However, PLLA's challenges, such as its lack of active surface functional groups and high hydrophobicity, impede endothelial cells' (ECs) attachment and growth. These factors subsequently amplify the risk of thrombosis and restenosis in PLLA implants. To counteract this problem, we've adapted the polydopamine (PDA) coating technique, a technique commonly used for metal stents. This method has demonstrated potential for promoting EC adhesion and proliferation on PLLA surfaces. Our study involved the application of PDA coating to PLLA, which resulted in improved EC attachment and proliferation while simultaneously inhibiting macrophage activation and the release of the inflammatory factor TNF-α. Additionally, the reactive functional groups on the PDA-coated surface provide a reactive platform for immobilizing therapeutic molecules onto PLLA, thereby further enhancing the biocompatibility of PLLA cardiovascular stents.

Investigating Cancerous Exosomes' Effects on CD8+ T-Cell IL-2 Production in a 3D Unidirectional Flow Bioreactor Using 3D Printed, RGD-Functionalized PLLA Scaffolds.

Exosomes from cancer cells are implicated in cancer progression and metastasis, carrying immunosuppressive factors that limit the antitumor abilities of immune cells. The development of a real-time, 3D cell/scaffold construct flow perfusion system has been explored as a novel tool in the study of T-cells and exosomes from cancer cells. Exosomes from human lung cancer (H1299 and A549) cells were co-cultured in a unidirectional flow bioreactor with CD8+ T-cells immobilized onto 3D-printed RGD-functionalized poly(L-lactic) acid (PLLA) scaffolds and assessed for IL-2 production. The IL-2 production was investigated for a wide range of T-cell to exosome ratios. With the successful incorporation of the RGD binding motif onto the PLLA surface at controllable densities, CD8+ T-cells were successfully attached onto 2D disks and 3D printed porous PLLA scaffolds. T-cell attachment increased with increasing RGD surface density. The diameter of the attached T-cells was 7.2 ± 0.2 µm for RGD densities below 0.5 nmoles/mm2 but dropped to 5.1 ± 0.3 µm when the RGD density was 2 nmoles/mm2 due to overcrowding. The higher the number of cancer exosomes, the less the IL-2 production by the surface-attached T-cells. In 2D disks, the IL-2 production was silenced for T-cell to exosome ratios higher than 1:10 in static conditions. IL-2 production silencing in static 3D porous scaffolds required ratios higher than 1:20. The incorporation of flow resulted in moderate to significant T-cell detachment. The portions of T-cells retained on the 3D scaffolds after exposure for 4 h to 0.15 or 1.5 mL/min of perfusion flow were 89 ± 11% and 30 ± 8%, respectively. On 3D scaffolds and in the presence of flow at 0.15 ml/min, both H1299 and A549 cancerous exosomes significantly suppressed IL-2 production for T-cell to exosome ratios of 1:1000. The much higher level of exosomes needed to silence the IL-2 production from T-cells cultured under unidirectional flow, compared to static conditions, denotes the importance of the culturing conditions and the hydrodynamic environment, on the interactions between CD8+ T-cells and cancer exosomes.

3D printed polylactic acid and acrylonitrile butadiene styrene fluidic structures for biological applications: Tailoring bio-material interface via surface modification

Three-dimensional (3D) printing is a rapidly growing technology that best fits for cell culture and other biological applications due to its potential to build immensely complex structures from customized designs. However, use of 3D printed structures for cell adhesion, proliferation, and activation requires tailoring of surface characteristics. In this context, this work investigates the use of two biocompatible 3D printable polymer materials, Poly-L-lactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS) for bio applications, and the effect of their post-printing surface modification processes to achieve desired bio functionality. Three post-printing surface modification techniques, alkaline hydrolysis, ultraviolet ozone plasma irradiation and gold thin film deposition are performed with the objective of introducing useful levels of surface functionalities. Poly-L-lysine (PLL) labelled with FITC chromophore is immobilized on the surface modified samples following standard protocols. The effect of surface roughness and porosity of the 3D printed structures on the polypeptide immobilization is compared on as-printed versus mechanically polished surfaces. Different characterization methods, viz., Fluorescence microscopy, Raman Spectroscopy and UV–vis spectroscopy, are used to study the efficacy of the surface modification and PLL immobilization techniques. Our results demonstrated denser PLL attachment on polished hydrolyzed PLA and ABS surfaces which enables the use of these printable polymers for a range of applications such as tissue scaffolds and microfluidics.

Enhanced Bioactivity of Micropatterned Hydroxyapatite Embedded Poly(L-lactic) Acid for a Load-Bearing Implant.

Poly(L-lactic) acid (PLLA) is among the most promising polymers for bone fixation, repair, and tissue engineering due to its biodegradability and relatively good mechanical strength. Despite these beneficial characteristics, its poor bioactivity often requires incorporation of bioactive ceramic materials. A bioresorbable composite made of PLLA and hydroxyapatite (HA) may improve biocompatibility but typically causes deterioration in mechanical properties, and bioactive coatings inevitably carry a risk of coating delamination. Therefore, in this study, we embedded micropatterned HA on the surface of PLLA to improve bioactivity while eliminating the risk of HA delamination. An HA pattern was successfully embedded in a PLLA matrix without degeneration of the matrix’s mechanical properties, thanks to a transfer technique involving conversion of Mg to HA. Furthermore, patterned HA/PLLA’s biological response outperformed that of pure PLLA. These results confirm patterned HA/PLLA as a candidate for wide acceptance in biodegradable load-bearing implant applications.

Immobilizing hydrolytic active Papain on biodegradable PLLA for biofilm inhibition in cardiovascular applications

Abstract The use of biomaterials in medicine is becoming increasingly important. One of the main concerns is the foreign body associated infection caused by direct microbial contamination or clinical infections. The bacterial biofilm formation on biomaterials depends on their surface properties. Therefore, several anti-adhesive surface modifications were developed. Nevertheless, the demand for antimicrobial agents that prevent bacterial colonisation is still largely unmet. The immobilization of active antimicrobial agents, such as antibacterial peptides or enzymes, offers a potential approach to achieve long-lasting effectiveness. In this investigation, the hydrolytic enzyme papain with its published antibacterial activity was covalently immobilized on the well-established biodegradable biomaterial poly-L-lactic acid (PLLA). For the characterization of the enzymes on the PLLA surfaces, the protein content and enzyme activity were determined. A biofilm assay was performed to test the effect of the papain-modified PLLA samples on the biofilm-forming bacterial strain Clostridioides difficile, one of the most frequently occurring human nosocomial pathogens. The investigated hydrolytic enzyme papain could be immobilized by coupling via the crosslinker EDC to the PLLA surface. Detection was performed by determination of the amount of protein and the reduced biofilm growth after 24 h and 72 h compared to the reference.

Immobilized Macrophage Colony-Stimulating Factor (M-CSF) Regulates the Foreign Body Response to Implanted Materials.

The functionality and durability of implanted biomaterials are often compromised by an exaggerated foreign body reaction (FBR). M1/M2 polarization of macrophages is a critical regulator of scaffold-induced FBR. Macrophage colony-stimulating factor (M-CSF), a hematopoietic growth factor, induces macrophages into an M2-like polarized state, leading to immunoregulation and promoting tissue repair. In the present study, we explored the immunomodulatory effects of surface bound M-CSF on poly-l-lactic acid (PLLA)-induced FBR. M-CSF was immobilized on the surface of PLLA via plasma immersion ion implantation (PIII). M-CSF functionalized PLLA, PLLA-only, and PLLA+PIII were assessed in an IL-1β luciferase reporter mouse to detect real-time levels of IL-1β expression, reflecting acute inflammation in vivo. Additionally, these different treated scaffolds were implanted subcutaneously into wild-type mice to explore the effect of M-CSF in polarization of M2-like macrophages (CD68+/CD206+), related cytokines (pro-inflammatory: IL-1β, TNF and MCP-1; anti-inflammatory: IL-10 and TGF-β), and angiogenesis (CD31) by immunofluorescent staining. Our data demonstrated that IL-1β activity in M-CSF functionalized scaffolds was ∼50% reduced compared to PLLA-only at day 1 (p < 0.01) and day 2 (p < 0.05) post-implantation. There were >2.6-fold more CD206+ macrophages in M-CSF functionalized PLLA compared to PLLA-only at day 7 (p < 0.001), along with higher levels of IL-10 at both day 7 (p < 0.05) and day 14 (p < 0.01), and TGF-β at day 3 (p < 0.05), day 7 (p < 0.05), and day 14 (p < 0.001). Lower levels of pro-inflammatory cytokines were also detected in M-CSF functionalized PLLA in the early phase of the immune response compared to PLLA-only: a ∼58% decrease at day 3 in IL-1β; a ∼91% decrease at day 3 and a ∼66% decrease at day 7 in TNF; and a ∼60% decrease at day 7 in MCP-1. Moreover, enhanced angiogenesis inside and on/near the scaffold was observed in M-CSF functionalized PLLA compared to PLLA-only at day 3 (p < 0.05) and day 7 (p < 0.05), respectively. Overall, M-CSF functionalized PLLA enhanced CD206+ macrophage polarization and angiogenesis, consistent with lower levels of pro-inflammatory cytokines and higher levels of anti-inflammatory cytokines in early stages of the host response, indicating potential immunoregulatory functions on the local environment.

Functionalization of PLLA with Polymer Brushes to Trigger the Assembly of Fibronectin into Nanonetworks.

Poly-l-lactic acid (PLLA) has been used as a biodegradable polymer for many years; the key characteristics of this polymer make it a versatile and useful resource for regenerative medicine. However, it is not inherently bioactive. Thus, here, a novel process is presented to functionalize PLLA surfaces with poly(ethyl acrylate) (PEA) brushes to provide biological functionality through PEA's ability to induce spontaneous organization of the extracellular matrix component fibronectin (FN) into physiological-like nanofibrils. This process allows control of surface biofunctionality while maintaining PLLA bulk properties (i.e., degradation profile, mechanical strength). The new approach is based on surface-initiated atomic transfer radical polymerization, which achieves a molecularly thin coating of PEA on top of the underlying PLLA. Beside surface characterization via atomic force microscopy, X-ray photoelectron spectroscopy and water contact angle to measure PEA grafting, the biological activity of this surface modification is investigated. PEA brushes trigger FN organization into nanofibrils, which retain their ability to enhance adhesion and differentiation of C2C12 cells. The results demonstrate the potential of this technology to engineer controlled microenvironments to tune cell fate via biologically active surface modification of an otherwise bioinert biodegradable polymer, gaining wide use in tissue engineering applications.

Biocompatibility of a PLA-based composite containing hydroxyapatite derived from waste bones of dolphin Neophocaena asiaeorientalis

Natural hydroxyapatite (HA), derived from waste bones of several animal species, has received much attention as a material for bone grafts and fillers and has a role as a coating for metal implants because of its biocompatibility and non-toxicity. To investigate the applicability of HA derived from waste bones of novel animal sources, the biocompatibility and toxicity of a poly-l-lactic acid (PLA)-based composite containing HA derived from the backbone of the dolphin Neophocaena asiaeorientalis (HANA) were examined in Sprague-Dawley (SD) rats. HANA powder showed X-ray diffraction peak patterns that corresponded to those of standard HA. Among five composites prepared from different combinations of PLA and HANA (7:3, 6:4, 5:5, 4:6, and 3:7), a PLA/HANA composite manufactured with a 6:4 PLA:HANA ratio had high surface roughness (453 nm), 10.3 N of maximum load, and 451.9 MPa of module elasticity. After implantation in the subcutaneous region of SD rats for 8 weeks, the amount of confluent, aggregated structures of multilayered cells on the PLA/HANA implant surface was greater than that on the PLA surface, although both implants were completely covered with adhesive cells. During the implant period, the initial intact form of the PLA/HANA composite broke into small fragments with few inflammatory cells in the contact region and no indication of significant toxicity. Taken together, the results suggest that HANA may have good biocompatibility and be non-toxic as it did not induce an immune response in SD rats.

Polydopamine-mediated surface modifications of poly l-lactic acid with hydroxyapatite, heparin and bone morphogenetic protein-2 and their effects on osseointegration

Surface modified poly l-lactic acid (PLLA) samples with hydroxyapatite (HA), heparin and bone morphogenetic protein-2 (BMP-2) mediated by polydopamine (pDA) coating (PLLA/pDA/HA/Hep/BMP-2) were prepared, and their effects on the enhancements of bone formation and osseointegration were evaluated in vitro and in vivo as compared to PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. The changes in surface chemical compositions, morphologies and wettabilities were observed by X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and water contact angle measurements. Pre-coating of HA particles with pDA provided uniform and homogeneous anchoring of particles to PLLA surface. In addition, the strong ionic interaction between heparin and pDA led PLLA surface readily heparinized for loading of BMP-2. In vitro experiments revealed that the levels of alkaline phosphatase (ALP) activity, calcium deposition, and osteocalcin (OCN) gene expression were higher in MG-63 human osteosarcoma cell lines grown on PLLA/pDA/HA/Hep/BMP-2 than on control PLLA, PLLA/pDA/HA, and PLLA/pDA/Hep/BMP-2. In vivo studies using micro-computed tomography (micro-CT) also showed that PLLA/pDA/HA/Hep/BMP-2 screw exhibited greatest value of bone volume (BV) and bone volume/tissue volume (BV/TV) among samples. Histological evaluations with H&E and Von Kossa staining demonstrated that a combination of HA and BMP-2 contributed to the strong osseointegration.

Surface Modification of PLLA Electrospun Nanofiber Materials for Biomedical Applications

Three dimensional nanofiber materials made of poly-L-lactic acid (PLLA) and produced by electrospinning are commonly used in regenerative medicine and as a base for drug delivery systems. Surface modification of such materials allows manipulating their chemical, physical, and biological properties. Previously, our group reported a number of modification strategies for thin PLLA films, based on the “solvent/non-solvent” technique. Most biologically active agents may not be adsorbed on the surface of PLLA. Proposed treatment allows partially dissolving the polymer surface in order to adsorb biologically active molecules or linkers. The aim of this work was to investigate the influence of solvent/non-solvent mixture composition on the morphology and crystal structure of the electrospun PLLA scaffolds and to select the solvent system for further scaffolds modification in order to impart them biological activity. PLLA scaffolds were treated with mixtures of toluene and ethanol in different compositions. By means of scanning electron microscopy, it was shown that solvent/non-solvent treatment had no critical effect on the morphology of the scaffolds. The results of X-ray diffraction analysis revealed that treatment of the scaffolds with investigated solvent systems did not lead to the formation of the additional phases and the size of the polymer crystallites as well. Thus, selected solvent system will be used for modification of the PLLA electrospun nanofiber material for biomedical application.

Morphological study of dynamic culture of thermosensitive collagen hydrogel in constructing tissue engineering complex

ABSTACTThe purpose of this study is to research the morphologies and functional characteristics of the cell-scaffold complex in vitro constructed under dynamic culture conditions. BMSCs were isolated from the long bones of Fischer344 rats, and performed in vitro amplification to the third generation as seed cells, together with thermosensitive collagen hydrogel (TCH) as cell adhesion matrix, and poly-L-lactic acid (PLLA) as scaffold, to construct cell-scaffold complex. The cell-scaffold complexes in the experiment group and the control group were then performed dynamic culture and static culture. After 7 d of in vitro culture, the complexes in the 2 groups were performed gross observation and SEM; meanwhile, the total DNA content in the complex was detected on D0,1,3, and 7 of culture. After cultured using these 2 ways, collagen could both wrap the PLLA scaffold, forming dense film-like structures on the PLLA surface. The total DNA contents in the cell-scaffold complex of the experiment group on D1,3, and 7 were significantly higher than the control group (P < 0.05). Compared with D0, the total DNA contents on D1,3, and 7 in both groups were gradually increased, but only the total DNA contents on D7 showed statistically significant difference than D0 (P < 0.05). TCH -PLLA fiber joint-constructed complex extracellular matrix had good biocompatibility, and dynamic culture could promote the distribution of BMSCs on the surface and inside the structure, thus promoting cell proliferation, so it could be used for the in vitro construction of tissue engineering complex.

Low-fouling electrospun PLLA films modified with zwitterionic poly(sulfobetaine methacrylate)-catechol conjugates

In this work, we modified a hydrophobic electrospun poly (l-lactic) acid (PLLA) film with poly (sulfobetaine methacrylate) (pSBMA)-catechol conjugates of different molecular weights to improve the biocompatibility of the film. These conjugates were synthesized via atom transfer radical polymerization. They consist of an ultra-low fouling pSBMA zwitterionic polymer with a surface-adhesive catechol moiety. X-ray photoelectron spectroscopy, contact angle and scanning electron microscopy experiments were performed to characterize films before and after modification with pSBMA-catechol conjugates. Enzyme-linked immunosorbent and fluorescently-labeled bovine serum albumin were used to study the interactions of proteins with these films. Results showed that low molecular weight zwitterionic pSBMA-catechol conjugates greatly discouraged protein adsorption as shown by use of single protein solutions on PLLA films when the modification was performed in ethanolic Tris-HCl solution. This work offers a convenient and effective method to modify electrospun PLLA films for biomedical applications. Statement of SignificanceIn this work, we report a convenient and effective method to modify electrospun PLLA films using pSBMA-catechol conjugates via “graft-to” for biomedical applications. After pSBMA modification, the PLLA surface becomes hydrophilic with low contact angle and protein adsorption. Results showed that lower molecular weight zwitterionic pSBMA-catechol conjugate led to lower contact angles and better nonfouling properties on PLLA films when the coating was performed in a solution containing ethanol.

Performance test of Nano-HA/PLLA composites for interface fixation

Objective: By in situ polymerization of poly-L-lactic acid (PLLA) and nano-hydroxyapatite (Nano-HA), and finding the best proportion of composite, so as to get ideal interface fixation material. Methods: According to a certain ratio (the mass fraction of Nano-HA, respectively, is 0%, 10%, 20%, 30% and 40%), composite PLLA and Nano-HA by in situ polymerization, and test the performance of this kind of new type of interface fixation such as, bending strength,compressive strength, elastic modulus, scanning electron microscopy (SEM) and degradation experiments in vitro. Then observe its mechanical properties, microstructure, the dispersion of Nano-HA in the PLLA and degradation rate of composite materials. Results: 1. Mechanical tests show that with the increase of Nano-HA content, the tensile strength decreases and the elastic modulus increases; with Nano-HA content of 20%, the bending strength of composite materials presents the peak value (156.8 MPa). 2. SEM scan shows the fracture surface of pure PLLA is relatively smooth; with Nano-HA content of 10%, the fracture surface shows a large number of dimples, and is obvious rough; with Nano-HA content of 20%, the fracture surface is uneven, forming a large number of dimples; with Nano-HA content of 30% or more, the fracture surface becomes more flat, and there are some small dimples. 3. Degradation experiments in vitro show the following: as the degradation time goes on, the pH values of degradation liquid is gradually reduced and the mechanical properties of composite materials also gradually have some decay. Conclusion: With Nano-HA content of 20%, the interface fixation material has a better mechanical properties and degradation properties. According to the best ratio, prepare Nano-HA/PLLA composite artificial materials with good performance.

Controlled biopolymer roughness induced by plasma and excimer laser treatment

A new method for biopolymer poly-L-lactic-acid (PLLA) surface nanostructuring with surface plasmon reso- nance appearance is proposed. The motivation of this work is to determine optimal conditions for rough or flat biopolymer surface which may find broad application in tissue engineering as biocompatible carrier for various types of cell lines. A combination of plasma pre-treatment with consequent excimer laser exposure is proposed as a method for increasing the roughness of PLLA surface and changing its morphology. The focus of this paper is to determine morphology changes in combination with mass loss changes. The ablation loss and morphology of PLLA was induced by excimer laser exposure of plasma pre-treated PLLA with different laser fluencies and number of pulses. The combination of a certain input parameters of plasma pre-treatment together with laser exposure induces extensive physico-chemical changes (morphology, contact angle, optical properties) on polymer surface with dramatic roughness increase. Gravimetric studies have revealed an extensive polymer ablation after excimer laser application. The effect of surface plasmon resonance was observed in laser modified PLLA. Conditions for PLLA surface flattening are also proposed.

The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA

Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment.

Heterofunctional nanosheet controlling cell adhesion properties by collagen coating

Recently, biomaterials have been widely used in a variety of medical applications. We previously reported that a poly-l-lactic acid (PLLA) nanosheet shows anti-adhesive properties and constitutes a useful biomaterial for preventing unwanted wound adhesion in surgical operations. In this article, we examine whether the PLLA nanosheet can be specifically modified with biomacromolecules on one surface only. Such an approach would endow each side of the nanosheet with discrete functions, that is anti-adhesive and pro-healing properties. We fabricated two distinct PLLA nanosheets: (i) collagen cast on the surface of a PLLA nanosheet (Col-Cast-PLLA) and (ii) collagen spin-coated on the nanosheet (Col-Spin-PLLA). In the Col-Spin-PLLA nanosheet, the collagen layer had a thickness of 5-10 nm on the PLLA surface and displayed increased hydrophilicity compared to both PLLA and Col-Cast-PLLA nanosheets. In addition, atomic force microscopy showed disorganized collagen fibril formation on the PLLA layer when covered using the spin-coating method, while apparent bundle formations of collagen were formed in the Col-Cast-PLLA nanosheet. The Col-Spin-PLLA nanosheet provided a microenvironment for cells to adhere and spread. By contrast, the Col-Cast-PLLA nanosheet displayed reduced cell adhesion compared to the Col-Spin-PLLA nanosheet. Consistent with these findings, immunocytochemical analysis clearly showed fine networks of actin filaments in cells cultured on the Col-Spin-PLLA, but not the Col-Cast-PLLA nanosheet. Therefore, the Col-Spin-PLLA nanosheet was shown to be more suitable for acting as a scaffold. In conclusion, we have succeeded in developing a heterofunctional nanosheet comprising a collagen modified side, which has the ability to rapidly adhere cells, and an unmodified side, which acts as an adhesion barrier, by using a spin-coating technique.

Biodegradable polymer solar cells

Polymer photovoltaic devices were prepared using a biodegradable poly- l-lactic acid (PLLA) substrate loaded with nanoclay in an attempt to improve the thermal properties and possibly reduce permeation of water and oxygen. The nanoclay-loaded PLLA substrates were prepared by compounding and extrusion. The substrate thickness was 200 μm and the substrates had good transparency in the range 300–800 nm of, respectively, >80% for PLA and >60% for PLLA loaded with nanoclay. Devices were realized by application of a conducting transparent anode comprising an aluminium grid with a thin overlayer of silver and spin-coated PEDOT:PSS. The active layer consisted of microfibrillar P3HT and PCBM to encompass the low processing temperatures for PLLA and finally an evaporated aluminium cathode. It was found that PLLA as a substrate holds potential, but there are several challenges beyond the photovoltaic itself which must be met before general application within this field can be envisaged. The most important aspects are the planarity of the PLLA surface, the mechanical stresses induced by the extrusion process, the limitation in processing temperature, and the limitation in the available range of solvents for solution processing.

Surface modification of poly-L-lactic acid films by electrostatic self-assembly to promote vascular smooth muscle cells growth

The intention of this study was to surface modify the poly-L-lactic acid (PLLA) film and evaluate the effects of the surfaces on the growth of vascular smooth muscle cells (VSMCs) in vitro. Collagen and hyaluronic acid (HA) were utilized as polycation and polyanion in this study. Layer-by-layer (LBL) self-assembly technique was used to lead to the formation of multilayer moleculer on the poly-L-lactic acid (PLLA) film surfaces. Collagen/HA layers was overcasted coating on the PLLA surface after the activation layers by poly-(ethyleneimine) (PEI). The structure and morphology of the multilayer molecular were examined by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrophotometer and atomic force microscope (AFM), respectively. The ATR-FTIR analysis illuminated the presence of collagen on the PLLA surface. The AFM results showed the multilayer appeared on PLLA surface. The VSMCs were adopted to evaluate the cyto-compatibility of the modified PLLA films. It was found that the viability of VSMCs on the modified PLLA films were greater than that on original PLLA films and tissue culture plastic after ten days culture (p < 0.05). Scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) data also confirmed the homogeneous results. These data suggest that collagen/HA coat can be successfully adopted in the surface modification of PLLA film through LBL technique, and also can enhance its cell compatibility.

Rapid hepatic cell attachment onto biodegradable polymer surfaces without toxicity using an avidin–biotin binding system

Efficient cell attachment to biodegradable polymer scaffolds is a necessary prerequisite in tissue engineering. However, it is difficult to evenly cover scaffold surfaces with cells because scaffolds are generally highly porous, with complex three-dimensional (3D) surfaces. In this article, we demonstrate the efficiency of avidin-biotin binding systems (ABBS) for the initial attachment of biotinylated Hep G2 cells to avidin adsorbed flat, two-dimensional (2D) and highly porous 3D poly L-lactic acid (PLLA) surfaces. The potential toxicity of biotinylation and/or strong ABBS binding forces was also investigated. ABBS assisted Hep G2 cells to adhere to a flat PLLA surface within 10min; the proliferation of these attached cells was comparable with control intact cells cultured on collagen. Hepatic functions of the attached cells, such as albumin secretion, induction of CYP1A1 and CYP1A2 genes, and metabolic capacity of CYP1A1/2 as measured by the ethoxyresorufin O-deethylase assay, were not significantly changed. Also, a stimulus of a cytokine: oncostatin M (OSM) phosphorylated an intracellular signaling molecule, extracellular signal-related kinase 1 (ERK1) via transmembrane receptor complex, at 24h after inoculation by ABBS. In addition, efficient attachment of Hep G2 cells to a highly porous PLLA 3D scaffold was demonstrated. These results clearly show that ABBS is useful for rapidly trapping cells in both biodegradable, polymer-based, flat 2D surfaces, and in highly porous 3D scaffolds. Furthermore, binding hepatic cells by this technique has only small effects on liver-specific functions, or on signal transfer ability of transmembrane receptor complexes.