PCL System Research Articles

Compostable lignin grafted poly(ε-caprolactone) polyurethane biomedical materials: Shape memory, foaming capabilities, and biocompatibility

Biodegradable shape memory poly(e-caprolactone) (PCL)-based polyurethane (PU) have garnered substantial attention in biomedical applications, due to their unique properties that can recover their original shapes when exposed to temperature stimulus close to body temperature (∼35 °C). This study entails an in situ one-pot synthesis of a compostable shape memory PU system that uses PCL as soft chain segments, 1,4-butanediol (BDO) and glycerol (GLY) as chain extenders, which was then grafted with lignin hard segment and/or crosslinking nodes. The addition of renewable and sustainable lignin not only enhanced the mechanical properties of the PU, but also improved the resulting shape memory effects by increasing the shape fixing and recovery ratio. In PCL system containing BDO (PCL-BDO), 5 wt% lignin loading yields shape fixity and shape recovery ratios of 93.2 % and 81.4 %, respectively. Similarly, 5 wt% lignin in PCL systems containing GLY (PCL-GLY exhibited high shape fixity (64.4 %) and shape recovery ratio (81.4 %), respectively. Rheological characterizations showed strong evidence that the melt strength of both the PCL-BDO and PCL-GLY increased with the presence of lignin, which directly improved the physical foaming capabilities of PCL-based PU. The biocompatibility assessment also showed that the developed shape memory PCL-lignin based PU were not cytotoxic and capable of supporting cell adhesion and cell growth.

Star-shaped poly(ε-caprolactones) with well-defined architecture as potential drug carriers

The present study reports the potential application of star-shaped poly(?-caprolactones) with different number of arms as new drug delivery matrix. Linear and star-shaped PCL ibuprofen loaded microspheres were prepared using oil-in-water (o/w) solvent evaporation technique and characterized with FTIR, DSC, XRD and SEM analysis. High yield, encapsulation efficiency and drug loadings were obtained for all microspheres. FTIR analysis revealed the existence of interactions between polymer matrix and drug, while the DSC analysis suggested that drug was encapsulated in an amorphous form. SEM analysis confirmed that regular, spherical in shape star-shaped microspheres, with diameter between 80 and 90 ?m, were obtained, while quite larger microspheres, 110 ?m, were prepared from linear PCL. The advantage of using starshaped PCL microspheres instead of linear PCL was seen from drug release profiles which demonstrated higher amount of drug released from star-shaped polymer matrix as a consequence of their branched, flexible structure. Microspheres prepared from the polymers with the most branched structure showed the highest amount of the released drug after 24 h. Finally, cytotoxicity tests, performed using normal human fibroblasts (MRC5), indicated the absence of cytotoxicity at lower concentrations of microspheres proving the great potential of star-shaped PCL systems in comparison to linear ones.

Counter-Passive Coherent Locator (C-PCL)—A Method of Remote Detection of Passive Radars for Electronic Warfare Systems

Passive Coherent Location methods and techniques have an established position in the modern state-of-the-art radar. Inexpensive, easy to deploy and undetectable for other sensors, passive radars are growing in popularity. Due to that, a need arises to develop proper methods of any possible kind of countermeasure. In this work, a method of detection and localization of hidden PCL systems is proposed. Authors exploit certain physical features of an RF receiver in order to detect such a passive systems. Results of selected hardware measurements are presented as a proof of concept. Summarized findings are followed by an extensive discussion of conditions related with the method implementation in a real world scenarios.

PLC Control System of Pneumatic Manipulator Automatic Assembly Line Based on Cloud Computing Platform

With the development of science and technology, cloud computing, big data and artificial intelligence and other new technologies have been applied in all aspects of life. The traditional manual tracking and processing production process has many defects. The application of computer technology to the production line to realize automatic production has the characteristics of high efficiency and integration. This paper studies the PLC control system of pneumatic robot automatic assembly line based on cloud computing platform system. In the research, we use PCL system to scan the data of automatic assembly of pneumatic manipulator processed by cloud computing platform, and write the program into the memory of PCL. At the same time, we connect the field input signal and the controlled actuator to the input end of the input module and the output end of the output module. The user can realize the automatic assembly by running the program. Compared with the number of Pneumatic Manipulators produced by manual production line, the system in this paper has high efficiency and superior performance. Thus, the PLC control system of pneumatic manipulator automatic assembly line based on cloud computing platform can improve the production efficiency.

Target Tracking Initiation for Multi-Static Multi-Frequency PCL System

In multiple target tracking, one of the crucial techniques is how to estimate unknown initiation points of tracks by incorporating a set of measurements under noisy and cluttered environment. Due to unknown data association and false alarms, all possible track initiation points need to be evaluated, which suffers from computational complexity. In this paper, we propose a computationally efficient track initiation method for multi-static multi-frequency passive coherent localization systems, where bistatic measurements from different illuminators are incorporated at a receiver to find the most probable track initiation points. By the proposed likelihood utility function, our method resolves unknown data association between measurements and targets to reduce computational complexity. In addition, the proposed method can be extended to process a set of multi-scan measurements in association-free manner, which results in improved estimation accuracy. Simulation results are provided to validate the performance of our proposed method.

A Passive Radar System for Monitoring of Coastal Areas Ship Traffic Using Satellite Illumination Signals

Introduction. Increasing requirements for improving of information systems for ensuring navigation safety in coastal areas of marine waters determine the search of new engineering and scientific solutions. The creation of a passive coherent location systems (PCL), based on existing sources of electromagnetic radiation (in particular, global navigation satellite system (GNSS) signals) as radar illumination of the monitored space is of particular interest. During development and implementation of the systems, there are a number of problems related to the search of highly efficient processing algorithms, to the optimization of structure and functioning modes when the system is a part of a complex multi-position monitoring system in coastal areas. Aim. Rationale of the structure of bistatic PCL system with GNSS illumination signal, analysis of methods for increasing of the level of reflected signals, development of a general signal processing algorithm of the system receiver unit, formation of proposals for the creation of multi-position radar system (MP radar) for coastal areas navigation monitoring. Materials and methods. Mathematical modeling, theory of signals, methods of digital signal processing. Results. The structure of the bistatic PCL with GNSS illumination signal for monitoring in coastal areas of marine waters to ensure navigation safety has been developed. Methods for increasing the power level of satellite signals at the input of the receiving device have been proposed. General signal processing algorithm and the algorithm of CAF calculation in the bistatic PCL system using GPS C/A code satellite signal for sea surface coastal areas monitoring have been developed. Conclusion. The considered bistatic PCL system with GNSS illumination may be applied as a part of MP radar for monitoring in areas of heavy vessel traffic to ensure the safety, for operational control of marine operations in the high seas, for quick analysis of the situation at sea in an emergency.

FDOA 정보 기반 멀티스태틱 PCL 시스템 위치추정 성능 분석

FDOA 정보 기반 멀티스태틱 PCL 시스템 위치추정 성능 분석

Lessons learned in the development of sustained release penicillin drug delivery systems for the prophylactic treatment of rheumatic heart disease (RHD).

The current prophylactic treatment to prevent rheumatic heart disease requires four-weekly intramuscular injection of a suspension of the poorly soluble benzathine salt form of penicillin G (BPG) often for more than 10years. In seeking to reduce the frequency of administration to improve adherence, biodegradable polymer matrices have been investigated. Poly(lactide-co-glycolide) (PLGA)-based in situ forming precursor systems containing N-methyl-2-pyrrolidone as solvent and PLGA-based monolithic implants for surgical implantation containing BPG were developed. Long-term release studies indicated low and plateaued release of penicillin G, but continual favourable release profiles for the benzathine counterion, indicating degradation of the polymer and generation of acidic microenvironment being detrimental to penicillin stability. In order to avoid the issue of theacidic product, poly(caprolactone)(PCL) implants were also investigated, with favourable penicillin G release behaviour being achieved, and slow release over 180days. However, when taking into account the mass of polymer, and the total dose of drug calculated from literature pharmacokinetic parameters for penicillin G, we concluded that an implant size of over 7g would still be required. This may preclude clinical deployment of a polymer matrix type delivery system for this indication in children and adolescents. Therefore, we have learned that biodegradable PLGA-type systems are not suitable for development of sustained release BPG treatments and that although the PCL system provides favourable release behaviour, the total size of the implant may still present a hurdle for future development.

Carvacrol encapsulation in starch or PCL based matrices by electrospinning

Carvacrol (CA) was encapsulated in polar (corn starch-Sodium caseinate, CS:NaCas) or non-polar (poly-ε-caprolactone, PCL) matrices by electrospinning (ES). Electrospunable formulations were prepared with CS:NaCas (9:1 w/w ratio), at 2, 4 and 6 wt % in water, or PCL at 5, 10 and 15 wt% in glacial acetic acid using different CA ratios (0, 5, 10 and 15 wt% with respect to the polymer). The liquid formulations were characterized for electrical conductivity, rheological behaviour and surface tension, and ES process conditions were established. The electrospun structures were analysed as to their nanostructure and CA retention. Geometry of the nanostructures obtained from the PCL systems was nanofibrillar with some beads, whereas it is particles that are mainly deposited for starch systems. PCL systems yielded better CA encapsulation efficiency (EE) than the polar ones, where greater variability was observed. The best EE (around 80%) was obtained for 15% PCL regardless of the CA ratio.

FM 신호 기반 PCL 시스템에서 간섭 신호 제거 알고리즘의 성능 분석

FM 신호 기반 PCL 시스템에서 간섭 신호 제거 알고리즘의 성능 분석

Characterization of chain dimensions of poly(ε-caprolactone) diols in THF by size-exclusion chromatography coupled with multi-angle light scattering (SEC-MALS)

In this work, we studied the chain dimensions, shape, and thermodynamic characteristics of poly(e-caprolactone) diols (HO-PCL-OH) in solution. PCL diol samples of different molecular weights and architectures were synthesized using immobilized Yarrowia lipolytica lipase as catalyst. Gel permeation chromatography (GPC) with online right-angle laser-light scattering (RALLS), differential viscometer (DV), and interferometric refractometer IRS detectors offered a proper way to obtain information on thermodynamic characteristics and chain flexibility. The weight-average molecular weights of the PCL diol samples (M w ) ranged from 2,750 to 13,120 uma. The z-average radius of hydrodynamic volume (<R h 2 > z 1/2 ) vs. z-average molecular weight curve (M z ) could be satisfactorily fitted to a power-law equation. Mark–Houwink–Sakurada parameters (K = 2.74 × 10−3 dL/g and a = 0.64) were derived from the plots of [η] w against M w . The overall results clearly suggest that a flexible geometry is present in tetrahydrofuran (THF) solution of PCL at 33 °C. Unlike other PCL systems, PCL diols are more hydrophilic and expected to form associated species. They behave differently from common hydrophobic polymers and do not strictly conform to thermodynamic relationships generally used in Polymer Science. A more compact geometry is present for Mn lower than 4,000 Da. For higher molecular weights, the chain expands and become more elongated. Plots of ln [η] w against ln M w (MHS equation) and of log R hz against log M z suggest that PCL diols behave as flexible chains in a good solvent.

Velocity measurement and traffic monitoring using a GSM passive radar demonstrator

The paper presented an idea for a new potential civilian application for passive radar utilizing a GSM transmitter as the illuminator of opportunity. The concept presented has been verified via the processing of the data recorded during a measurement campaign carried out in a real operational scenario. The results presented in the paper show that a GSM-based PCL system can be used successfully in the future as a new system dedicated to speed control and traffic monitoring, both in urban areas and on small roads and highways. The results presented in the paper show that the system is able to simultaneously distinguish different-sized objects, characterized by different RCSs, as in the example of the truck and cyclist. This result shows the high potential of the proposed system.

Novel semi-interpenetrating hydrogel networks with enhanced mechanical properties and thermoresponsive engineered drug delivery, designed as bioactive endotracheal tube biomaterials

Thermoresponsive polymeric platforms are used to optimise drug delivery in pharmaceutical systems and bioactive medical devices. However, the practical application of these systems is compromised by their poor mechanical properties. This study describes the design of thermoresponsive semi-interpenetrating polymer networks (s-IPNs) based on cross-linked p(NIPAA) or p(NIPAA-co-HEMA) hydrogels containing poly(ε-caprolactone) designed to address this issue. Using DSC, the lower critical solution temperature of the co-polymer and p(NIPAA) matrices were circa 34°C and 32°C, respectively. PCL was physically dispersed within the hydrogel matrices as confirmed using confocal scanning laser microscopy and DSC and resulted in marked changes in the mechanical properties (ultimate tensile strength, Young’s modulus) without adversely compromising the elongation properties. P(NIPAA) networks containing dispersed PCL exhibited thermoresponsive swelling properties following immersion in buffer (pH 7), with the equilibrium-swelling ratio being greater at 20°C than 37°C and greatest for p(NIPAA)/PCL systems at 20°C. The incorporation of PCL significantly lowered the equilibrium swelling ratio of the various networks but this was not deemed practically significant for s-IPNs based on p(NIPAA). Thermoresponsive release of metronidazole was observed from s-IPN composed of p(NIPAA)/PCL at 37°C but not from p(NIPAA-co-HEMA)/PCL at this temperature. In all other platforms, drug release at 20°C was significantly similar to that at 37°C and was diffusion controlled. This study has uniquely described a strategy by which thermoresponsive drug release may be performed from polymeric platforms with highly elastic properties. It is proposed that these materials may be used clinically as bioactive endotracheal tubes, designed to offer enhanced resistance to ventilator associated pneumonia, a clinical condition associated with the use of endotracheal tubes where stimulus responsive drug release from biomaterials of significant mechanical properties would be advantageous.

A Study of the Electrospinning of an H2O–Acetone–PCL Ternary System

The aim of this study was to investigate the electrospinning of a ternary system consisting of water, acetone, and poly(e-caprolactone) (PCL) in order to prepare bead/block-type nano/microfibres as innovative cell-growth scaffolds with potentially controllable drug-releasing capabilities. Experimental cloud point data were obtained by cloud point titration. The phase diagram for the ternary H2O–acetone–PCL system was determined from the cloud point data. The ternary phase diagram can be used to investigate the mechanism of fibre formation, which is unlike that of traditional electrospun fibres. Bead-like nano/microfibres of the given ternary system were successfully fabricated by electrospinning.

Mesoporous Carbons from Poly(acrylonitrile)-b-poly(ε-caprolactone) Block Copolymers

A series of degradable block copolymers, poly(acrylonitrile)-b-poly(ε-caprolactone) (PAN−PCL), have been synthesized by sequential living polymerization in this study. Well-defined, microphase-separated PAN−PCL microdomains can be efficiently achieved in the bulk by using appropriate solvents. The microphase-separated lamellar samples were then used as templates to produce mesoporous carbons at which large amounts of porous texture in carbonized PAN matrix were formed after degradation of PCL due to randomly oriented lamellar texture (namely, interconnection of PCL microdomains). The thermal profiles for efficient stabilization were examined by differential scanning calorimetry and thermogravimetric analyses as well as Fourier transform infrared spectroscopy. Consequently, mesoporous carbon materials might be prepared as evidenced by transmission electron microscopy, field emission scanning electron microscopy, and small-angle X-ray scattering. The formation of carbonized materials was identified in accordance with the presence of carbon diffractions by wide-angle X-ray diffraction. In contrast to the thermal stability of the carbonization of PAN homopolymers, it is noted that the carbonization procedure can be achieved in the PAN−PCL system regardless of the stretching process (that is an essential process to improve the thermal stability of PAN carbonization). We speculate that this unique feature for the carbonization of PAN copolymers might be attributed to the stretched chains of PAN under nanoscale confined environment.

Synthesis of star-shaped poly(ε-caprolactone) by samarium-based tetrafunctional initiator and its dilute-solution properties

An in situ–generated tetrafunctional samarium enolate from the reduction of 1,1,1,1-tetra(2-bromoisobutyryloxymethyl)methane with divalent samarium complexes [Sm(PPh2)2 and SmI2] in tetrahydrofuran has proven to initiate the ring-opening polymerization of ϵ-caprolactone (CL) giving star-shaped aliphatic polyesters. The polymerization proceeded with quantitative conversions at room temperature in 2 h and exhibited good controllability of the molecular weight of polymer. The resulting four-armed poly(ϵ-caprolactone) (PCL) was fractionated, and the dilute-solution properties of the fractions were studied in tetrahydrofuran and toluene at 30°C. The Mark–Houwink relations for these solvents were [η] = 2.73 × 10−2Mw0.74 and [η] = 1.97 × 10−2Mw0.75, respectively. In addition, the unperturbed dimensions of the star-shaped PCL systems were also evaluated, and a significant solvent effect was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 175–182, 2006

A novel gene transfer strategy that combines promoter and transgene activities for improved tumor cell inhibition

Typically, gene transfer strategies utilize a promoter/transgene arrangement that treat these elements independently and do not offer any interplay between them. Our goal was to establish a promoter/transgene combination that would result in improvement in both expression and therapeutic effect by utilizing the transcriptional properties of p53 to drive its own expression as well as act as a tumor suppressor. The pCL retroviral system was modified in the U3 region of the 3' LTR by the addition of a p53-responsive sequence (the PG element), creating the pCLPG system. Upon reverse transcription, the 5' LTR is converted, as shown here, to a p53-dependent promoter. We also show, using a temperature-sensitive model, that the pCLPG system could be driven by p53 encoded within the virus construct and expression was modulated depending on the p53 phenotype, demonstrating a regulatory feedback loop. Moreover, the pCLPG system was shown to express the transgene at a higher level and to inhibit tumor cell proliferation more robustly than the original pCL system. This novel system employs the transgene to serve two purposes, drive viral expression and inhibit tumor cell proliferation. The pCLPG vectors represent a new gene transfer strategy of synergizing the promoter and transgene activities.

Exploration of critical parameters for transient retrovirus production

The pCL system was developed to aid in the production of retrovirus that encodes cytotoxic or cytostatic cDNA's. A principal feature of this system is the transient production of virus after co-transfection of the viral and packaging vectors in the 293T cell line. This approach obviates the need for selection of the producer cells, thus minimizing potential affects of the encoded genes. However, the transient nature of this system also creates a number of experimental variables. In this study we have examined and optimized elements related to the production of the pCL retrovirus. For example, co-transfection of the packaging sequence along with the viral vector has been optimized in terms of both the total amount of DNA transfected and the relative proportion of each plasmid. We have also tested the affect of increased synthesis of viral proteins in the producer cells and the kinetics of virus accumulation in the supernatant. These findings may be of interest to those who use pCL or any transient packaging system in their gene transfer studies. In addition, these studies may aid in the validation and development of transient retrovirus production systems for clinical applications.

Glass transitions and interactions in polymer blends containing poly(4-hydroxystyrene) brominated

The miscibility and interactions of binary blends of poly(4-hydroxystyrene) brominated (P4HSBR) with poly(ϵ-caprolactone) (PCL), poly(vinyl acetate) (PVA) and poly(vinyl methylether) (PVME) are investigated by means of differential scanning calorimetry (DSC). Glass transition temperatures, T gs, are used to assess the miscibility of these systems. All of them were found to be miscible over the whole composition range. T gs of the blends are lower than Fox predictions, in contrast to the results previously obtained for systems involving poly(4-hydroxystyrene) (P4HS). The melting of PCL in the blends was studied. From the melting temperature depression of PCL in the blends the polymer–polymer interaction parameter was obtained and compared with the ones obtained for P4HS/PCL and poly(4-hydroxystyrene-co-methoxystyrene) (P4HSM)/PCL systems. The best interactions are achieved in P4HS/PCL and the bromination or methoxylation of the P4HS worsen the interactions with the PCL. The presence of a cusp in the T g-composition curve was analysed in terms of the Kovacs' theory in systems with P4HS and P4HSBR.

The pCL vector system: rapid production of helper-free, high-titer, recombinant retroviruses.

We describe the construction and characterization of retroviral vectors and packaging plasmids that produce helper-free retrovirus with titers of 1 X 10(6) to 5 X 10(6) within 48 h. These vectors contain the immediate early region of the human cytomegalovirus enhancer-promoter fused to the Moloney murine leukemia virus long terminal repeat at the TATA box in the 5' U3 region, yielding the pCL promoter. By selecting vectors designed to express genes from one of four promoters (dihydrofolate reductase, Rous sarcoma virus, long terminal repeat, or cytomegalovirus), the pCL system permits the investigator to control the level of gene expression in target cells over a 100-fold range, while maintaining uniformly high titers of virus from transiently transfected producer cells. The pCL packaging plasmids lack a packaging signal (delta-psi) and include an added safety modification that renders them self-inactivating through the deletion of the 3' U3 enhancer. Ecotropic, amphotropic (4070A), and amphotropic-mink cell focus-forming hybrid (10A1) envelope constructions have been prepared and tested, permitting flexible selection of vector pseudotype in accordance with experimental needs. Vector supernatants are free of helper virus and are of sufficiently high titer within 2 days of transient transfection in 293 cells to permit infection of more than 50% of randomly cycling target cells in culture. We demonstrated the efficacy of these vectors by using them to transfer three potent cell cycle control genes (the p16(INK4A), p53, and Rb1 genes) into human glioblastoma cells.