Oligopeptide-based molecular labelling of (bio)degradable polyester biomaterials

Nowadays, a very important motivation for the development of new functional materials for medical purposes is not only their performance but also whether they are environmentally friendly. In recent years, there has been a growing interest in the possibility of labelling (bio)degradable polymers, in particular those intended for specific applications, especially in the medical sector, and the potential of information storage in such polymers, making it possible, for example, to track the ultimate environmental fate of plastics. This article presents a straightforward green approach that combines both aspects using an oligopeptide, which is an integral part of polymer material, to store binary information in a physical mixture of polymer and oligopeptide. In the proposed procedure the year of production of polymer films made of poly(l-lactide) (PLLA) and a blend of poly(1,4-butylene adipate-co-1,4-butylene terephthalate) and polylactide (PBAT/PLA) were encoded as the sequence of the appropriate amino acids in the oligopeptide (PEP) added to these polymers. The decoding of the recorded information was carried out using mass spectrometry technique as a new method of decoding, which enabled the successful retrieval and reading of the stored information. Furthermore, the properties of labelled (bio)degradable polymer films and stability during biodegradation of PLLA/PEP film under industrial composting conditions have been investigated. The labelled films exhibited good oligopeptide stability, allowing the recorded information to be retrieved from a green polymer/oligopeptide system before and after biodegradation. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay) study of the PLLA and PLLA/PBAT using the MRC-5 mammalian fibroblasts was presented for the first time.

Designing of Drug Delivery Systems to Improve the Antimicrobial Efficacy in the Periodontal Pocket Based on Biodegradable Polyesters

Delivery systems for biologically active substances such as proanthocyanidins (PCANs), produced in the form of electrospun nonwoven through the electrospinning method, were designed using a polymeric blend of poly(L-lactide-co-glycolide) (PLGA)and poly[(R,S)-3-hydroxybutyrate] ((R,S)-PHB). The studies involved the structural and thermal characteristics of the developed electrospun three-dimensional fibre matrices unloaded and loaded with PCANs. In the next step, the hydrolytic degradation tests of these systems were performed. The release profile of PCANs from the electrospun nonwoven was determined with the aid of UV-VIS spectroscopy. Approximately 30% of the PCANs were released from the tested electrospun nonwoven during the initial 15-20 days of incubation. The chemical structure of water-soluble oligomers that were formed after the hydrolytic degradation of the developed delivery system was identified through electrospray ionization mass spectrometry. Oligomers of lactic acid and OLAGA oligocopolyester, as well as oligo-3-hydroxybutyrate terminated with hydroxyl and carboxyl end groups, were recognized as degradation products released into the water during the incubation time. It was also demonstrated that variations in the degradation rate of individual mat components influenced the degradation pattern and the number of formed oligomers. The obtained results suggest that the incorporation of proanthocyanidins into the system slowed down the hydrolytic degradation process of the poly(L-lactide-co-glycolide)/poly[(R,S)-3-hydroxybutyrate] three-dimensional fibre matrix. In addition, in vitro cytotoxicity and antimicrobial studies advocate the use of PCANs for biomedical applications with promising antimicrobial activity.

Development of Polyhydroxybutyrate-Based Packaging Films and Methods to Their Ultrasonic Welding

This study developed a technical task associated with the formation of welded joints based on biodegradable polymers and their subsequent physicochemical characterization. The primary objective was to establish the effect of the welding process and modification of natural poly(3-hydroxybutyrate) (PHB) with N,N-dibutylundecenoylamide (DBUA) as a plasticizing agent on the structure and properties of PHB-based biopolymer materials as well as the process and structure of welded joints formation using ultrasonic welding technique. The weldability of biodegradable layers based on PHB and PHB/DBUA mixture was ultrasonically welded and optimized using a standard Branson press-type installation. The effect of the DBUA plasticizer and welding process on the structure of PHB-based biodegradable material was investigated using scanning electron microscopy, X-ray diffraction, FT-IR spectroscopy, differential scanning calorimetry, and thermomechanical analysis. The results confirmed that the DBUA acted as an effective plasticizer of PHB, contributing to lower crystallinity of the PHB/DBUA mixture (63%) in relation to the crystallinity degree of pure PHB film (69%). Ultrasonic welding resulted in an additional increase (approximately 8.5%) in the degree of crystallinity in the PHB/DBUA in relation to the initial PHB/DBUA mixture. The significant shift toward lower temperatures of the crystallization and melting peaks of PHB modified with DBUA were observed using DSC concerning pure PHB. The melt crystallization process of PHB was affected by welding treatment, and a shift toward higher temperature was observed compared with the unwelded PHB/DBUA sample. The butt-welded joints of biodegradable PHB/DBUA materials made using the ultrasonic method tested for tensile strength have damaged the area immediately outside the joining surface.

Surface Modification of PHBV Fibrous Scaffold via Lithium Borohydride Reduction

In this study, lithium borohydride (LiBH₄) reduction was used to modify the surface chemistry of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibers. Although the most common reaction employed in the surface treatment of polyester materials is hydrolysis, it is not suitable for fiber modification of bacterial polyesters, which are highly resistant to this type of reaction. The use of LiBH₄ allowed the formation of surface hydroxyl groups under very mild conditions, which was crucial for maintaining the fibers' integrity. The presence of these groups resulted in a noticeable improvement in the surface hydrophilicity of PHBV, as revealed by contact angle measurements. After the treatment with a LiBH₄ solution, the electrospun PHBV fibrous mat had a significantly greater number of viable osteoblast-like cells (SaOS-2 cell line) than the untreated mat. Moreover, the results of the cell proliferation measurements correlated well with the observed cell morphology. The most flattened SaOS-2 cells were found on the surface that supported the best cell attachment. Most importantly, the results of our study indicated that the degree of surface modification could be controlled by changing the degradation time and concentration of the borohydride solution. This was of great importance since it allowed optimization of the surface properties to achieve the highest cell-proliferation capacity.

From Anionic Ring-Opening Polymerization of β-Butyrolactone to Biodegradable Poly(hydroxyalkanoate)s: Our Contributions in This Field

The feasibility of synthesis of functionalized poly(3-hydroxybutanoic acid) analogue and its copolymers via ring-opening polymerization of β-butyrolactone mediated by activated anionic initiators is presented. Using these new synthetic approaches, polyesters with a defined chemical structure of the end groups, as well as block, graft, and random copolymers, have been obtained and characterized by modern instrumental techniques, with special emphasis on ESI-MS. The relationship between the structure and properties of the prepared polymeric materials is also discussed.

Towards Advances in Molecular Understanding of Boric Acid Biocatalyzed Ring-Opening (Co)Polymerization of δ-Valerolactone in the Presence of Ethylene Glycol as an Initiator

Following our previous studies on the molecular level structure of (co)oligoesters obtained via anionic homo- and co-polymerization of novel β-substituted β-lactones, prepared by the atmospheric pressure carbonylation reaction of respective epoxides, the boric acid biocatalyzed ring-opening (co)polymerization of δ-valerolactone has been studied. As a co-monomer the 6-methy-ε-caprolactone, prepared by the one-pot oxidation of respective alcohol, and ethylene glycol as polymerization initiator were used. The obtained copolymers were characterized by 1H-NMR, GPC and ESI-MS, respectively in order to confirm their chemical structures and identity. Subsequently, tandem mass spectrometry (MS-MS studies) via collision-induced dissociation were utilized to characterize the fragmentation pattern. ESI-MS and NMR analyses confirmed the formation of random linear copolymer chains composed of different polyester repeat units. MS-MS experiments showed that fragmentation proceeds via ester bound cleavage along the (co)polyester chains. The innovative aspect of this contribution is related to the elaboration of the telechelic (co)polymers end-capped with hydroxyl end groups and well-defined molecular architectures, which could facilitate the development of new flexible macromolecular systems for potential biomedical applications.

Gellan gum hydrogels cross-linked with carbodiimide stimulates vacuolation of human tooth-derived stem cells in vitro

The natural polysaccharides are promising compounds for applications in regenerative medicine. Gellan gum (GG) is the bacteria-derived polysaccharide widely used in food industry. Simple modifications of its chemical properties make GG superior for the development of biocompatible hydrogels. Beside reversible cationic integration of GG chains, more efficient binding is accomplished with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). However, the side-products of polymer cross-linking might affect viability and differentiation of stem cells introduced into the hydrogels. We found that O-acylisourea (EDU) stimulates autophagy-based vacuolation in both periodontal ligament and dental pulp stem cells. 24-h treatment of cells with GG extracts cross-linked with 15 mM EDC developed large cytoplasmic vacuoles. Freshly prepared EDU (2-6 mM) but not 15 mM EDC solutions initiated vacuole development with concomitant reduction of cell viability/metabolism. Most of the vacuoles stained with acridine orange displayed highly acidic environment further confirmed by flow cytometric analysis. Western blot of the LC3 autophagy marker followed by a transmission electron microscopy indicated the process is autophagy-dependent. We propose that the high reactivity of EDU with intracellular components initiates autophagy, although the targets of EDU remain unknown. Nevertheless, a burst release of EDU from GG hydrogels might modulate negatively cellular processes and final effectiveness of tissue regeneration.

Forensic Engineering of Advanced Polymeric Materials-Part VII: Degradation of Biopolymer Welded Joints

Welding technology may be considered as a promising processing method for the formation of packaging products from biopolymers. However, the welding processes used can change the properties of the polymer materials, especially in the region of the weld. In this contribution, the impact of the welding process on the structure and properties of biopolymer welds and their ability to undergo hydrolytic degradation will be discussed. Samples for the study were made from polylactide (PLA) and poly(3-hydroxyalkanoate) (PHA) biopolymers which were welded using two methods: ultrasonic and heated tool welding. Differential scanning calorimetry (DSC) analysis showed slight changes in the thermal properties of the samples resulting from the processing and welding method used. The results of hydrolytic degradation indicated that welds of selected biopolymers started to degrade faster than unwelded parts of the samples. The structure of degradation products at the molecular level was confirmed using mass spectrometry. It was found that hydrolysis of the PLA and PHA welds occurs via the random ester bond cleavage and leads to the formation of PLA and PHA oligomers terminated by hydroxyl and carboxyl end groups, similarly to as previously observed for unwelded PLA and PHA-based materials.

Effective Control against Broadleaf Weed Species Provided by Biodegradable PBAT/PLA Mulch Film Embedded with the Herbicide 2-Methyl-4-Chlorophenoxyacetic Acid (MCPA)

Biodegradable mulches are considered a promising alternative to polyethylene-based, nonbiodegradable mulch for sustainable agriculture. In the present study, a bioactive 2-methyl-4- cholorophenoxyacetic acid/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (MCPA-PHBV) conjugate blended with biodegradable poly(butylene adipate-co-terephthalate/polylactide (PBAT/PLA) was developed and used as mulch under controlled condition greenhouse pot experiment with fava bean (Vicia faba) as the nontarget crop species. The objectives were to examine the effectiveness of sustained-release of MCPA herbicide from biodegradable mulch for broadleaf weed suppression and to assess any adverse effects of the herbicide on the nontarget species (fava bean). The energy-dispersive X-ray spectroscopy analysis (EDS) suggests that a substantial quantity of the herbicide was released from the biodegradable mulch which effectively killed the broadleaf weed species even at 1% MCPA concentration. However, the higher concentrations of the herbicide adversely affected several physiological parameters of fava bean growth and development. Stomatal conductance decreased, while leaf temperature subsequently rose (at MCPA concentrations 5, 7.5, and 10%). The quantum yield of the Photosystem II (PSII) indicates that the photosynthetic efficiency was also restricted at concentrations 7.5% and 10%. Evidently, this slow-release herbicide system worked efficiently for broadleaf weed control but at higher concentrations, resulted in adverse physiological effects on the nontarget crop species. This study has demonstrated that biodegradable mulches containing MCPA herbicide are able to effectively inhibit the growth of broad leaf weed species and may be of potential importance in a wide variety of horticultural and agricultural applications.

Prediction studies of environment-friendly biodegradable polymeric packaging based on PLA. Influence of specimens' thickness on the hydrolytic degradation profile

Application of new biodegradable polymer packaging based on polylactide (PLA), susceptible to organic recycling, can help in the waste reduction in landfills. In this paper, the results of the study on abiotic degradation of PLA and its blend containing 15 mol% of poly[(R,S)-3-hydroxybutyrate], as a model for the first step of organic recycling were presented. The samples used for this study have different shapes and thicknesses: rigid films and cuboid-bars. Particular emphasis was placed on determining the pattern of degradation products released into the medium. Originally, the results of present study revealed that the application of electrospray ionization mass spectrometry supported by high performance liquid chromatography allowed envisaging the differences in the degradation products pattern released from the studied PLA-based samples differing in thickness. The significant differences in degradation products pattern were predominately observed in the first steps of incubation process and are caused by an autocatalytic effect, which occurs mainly during degradation of the large size PLA samples. Although, the thickness of PLA-based packaging changes the degradation product patterns, however this does not increase the total amounts of acids released to the medium. Thus, it may be concluded that thickness should not affect significantly organic recycling of the packaging.

Tandem mass spectroscopy as a tool for investigation of complexes of PNP-lariat ether derivative with metal ions

The novel PNP-lariat ether L with cyclotriphosphazene ring incorporated in the macrocyclic structure was synthesized and checked by the electrospray mass spectrometry (ESI-MS) method for the ability to bind different types of ions Ag⁺ , Ca²⁺ , Cd²⁺ , Cu²⁺ , and Pb²⁺ . Furthermore, the stability constants of the abovementioned ion complexes with the investigated ligand have been determined by direct and competitive potentiometric methods. To evaluate the stability of various complex types and to confirm the way of metal cation binding, the tandem mass spectra of the investigated ligand and its complexes were taken. As a result, we obtained quite a good relationship between the number and main types of complex species observed in ESI-MS experiments and the forms of complexes for which the stabilization constants were determined by potentiometric methods. Moreover, we also concluded that in case of big discrepancies of stability constants, ESI-MS experiments could provide information about the most stable form of the complexes, but they fail when the differences between the strength of the coordination binding are slightly different.

The Synthesis and Structural Characterization of Graft Copolymers Composed of γ-PGA Backbone and Oligoesters Pendant Chains

The novel copolymers composed of poly-γ-glutamic acid (γ-PGA) and oligoesters have been developed. The structures of the obtained copolymers including variety of end groups were determined at the molecular level with the aid of electrospray ionization multistage mass spectrometry (ESI-MSⁿ). The fragmentation experiment performed for the selected sodium adducts of the copolymers confirmed that the developed methods lead to the formation of graft copolymers composed of poly-γ-glutamic acid (γ-PGA) backbone and oligoesters pendant chains. Moreover, it was established that fragmentation of selected sodium adducts of graft copolymers proceeded via random breakage of amide bonds along the backbone and ester bonds of the oligoesters pendant chains. Considering potential applications of the synthesized copolymers in the area of biomaterials, the hydrolytic degradation under laboratory conditions and in vitro cytotoxicity tests were performed. The ESI-MSⁿ technique applied in this study has been proven to be a useful tool in structural studies of novel graft copolymers as well as their degradation products. Graphical Abstract ᅟ.

Forensic Engineering of Advanced Polymeric Materials-Part V: Prediction Studies of Aliphatic⁻Aromatic Copolyester and Polylactide Commercial Blends in View of Potential Applications as Compostable Cosmetic Packages

The main aim of the present study was to determine the behavior of the specimens from Ecovio, in the form of dumbbell-shaped samples and films, during degradation in selected cosmetic ingredients such as water and paraffin. The (bio)degradation test of the prototype cosmetic package (sachet) made from a PBAT (poly[(1,4-butylene adipate)–co–(1,4-butylene terephthalate)]) and PLA (polylactide) blend was investigated under industrial composting conditions, and compared with the sample behavior during incubation in cosmetic media at 70 °C. During the degradation tests, the changes of the samples were evaluated using optical microscopy, ¹H NMR (proton nuclear magnetic resonance) and GPC (gel permeation chromatography) techniques. The structures of the degradation products were investigated using ESI-MSⁿ (mass spectrometry with electrospray ionization on positive and negative ions) analysis. The thermal properties of selected materials were determined by DSC (differential scanning calorimetry) and TGA (thermogravimetric analysis) analysis. It was concluded that the PBAT and PLA blend studied had a good stability during aging in cosmetic media, and could be recommended for long-shelf-life compostable packaging of cosmetics, especially with oily ingredients.

Intraocular Transplantation of E1A-Immortalized Retinal Precursor Cells

The purpose of this study was to examine the effect of the ocular environment on the survival, tumorigenicity, and phenotypic marker expression of immortalized retinal precursor cells transplanted into immunocompetent adult and neonatal Sprague–Dawley rats. E1A-NR.3, a rat immortalized retinal precursor cell culture, was used as an inexhaustible source of experimental graft material. These cells were prelabeled with the fluorescent marker diI (1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate) and transplanted intravitreally (50,000 cells per μL) into 11 adult and 31 neonatal Sprague–Dawley rat eyes. At 1 mo posttransplant, animals were sacrificed and retinal tissue sections examined histologically for the presence of grafted cells, signs of tumor formation, and retinal phenotypic marker expression. No obvious signs of tumor formation or rejection were seen in a total of 42 eyes in the immunocompetent hosts. Our results indicate that E1A-NR.3 cells survive at least 1 month in vivo, and can migrate from the vitreous into neuroretinal cell layers. Subpopulations of surviving grafted cells were seen to express photoreceptor markers rhodopsin and recoverin comparably between in vitro and in vivo conditions. However, the number of cells immunoreactive for vimentin and E1A decreased significantly under in vivo conditions. This report represents the first experimental intravitreal transplantation of E1A-immortalized retinal precursor cells into adult and neonatal rats. The intraocular location and environment appears to affect phenotypic expression of surviving grafted cells, especially with respect to vimentin and E1A expression. The fact that E1A-NR.3 cells survived intraocularly at least 1 mo without tumor formation suggests that the cells may continue to be useful for further in vivo studies of experimental retinal transplantation, and effects of histological location on retinal cell phenotype and histogenesis in immunocompetent hosts. © 1998 Elsevier Science Inc.

Biocompatible terpolyesters containing polyhydroxyalkanoate and sebacic acid structural segments – synthesis and characterization

A convenient synthetic route of poly(3HB-co-3HH-co-SEB) terpolyesters has been reported.

Synthesis and Structural Characterization of Bioactive PHA and γ-PGA Oligomers for Potential Applications as a Delivery System

The (trans)esterification reaction of bacterial biopolymers with a selected bioactive compound with a hydroxyl group was applied as a convenient method for obtaining conjugates of such compound. Tyrosol, a naturally occurring phenolic compound, was selected as a model of a bioactive compound with a hydroxyl group. Selected biodegradable polyester and polyamide, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) and poly-γ-glutamic acid (γ-PGA), respectively, were used. The (trans)esterification reactions were carried out in melt mediated by 4-toluenesulfonic acid monohydrate. The structures of (trans)esterification products were established at the molecular level with the aid of ESI-MS² (electrospray ionization tandem mass spectrometry) and/or ¹H NMR (nuclear magnetic resonance) techniques. Performed analyses confirmed that the developed method leads to the formation of conjugates in which bioactive compounds are covalently bonded to biopolymer chains. The amount of covalently bonded bioactive compounds in the resulting conjugates depends on the type of biopolymers applied in synthesis.

Mass spectrometry for the elucidation of the subtle molecular structure of biodegradable polymers and their degradation products

Contemporary reports by Polish authors on the application of mass spectrometric methods for the elucidation of the subtle molecular structure of biodegradable polymers and their degradation products will be presented. Special emphasis will be given to natural aliphatic (co)polyesters (PHA) and their synthetic analogues, formed through anionic ring-opening polymerization (ROP) of β-substituted β-lactones. Moreover, the application of MS techniques for the evaluation of the structure of biodegradable polymers obtained in ionic and coordination polymerization of cyclic ethers and esters as well as products of step-growth polymerization, in which bifunctional or multifunctional monomers react to form oligomers and eventually long chain polymers, will be discussed. Furthermore, the application of modern MS techniques for the assessment of polymer degradation products, frequently bearing characteristic end groups that can be revealed and differentiated by MS, will be discussed within the context of specific degradation pathways. Finally, recent Polish accomplishments in the area of mass spectrometry will be outlined.

Molecular architecture of novel potentially bioactive (co)oligoesters containing pesticide moieties established by electrospray ionization multistage mass spectrometry

RATIONALE

Pesticides are commonly used in agriculture to ensure high crop yield; however, because of their low resistance to environmental conditions, a large amount of pesticides does not reach target pests and becomes an environmental pollutant. One of the ways to reduce these drawbacks is synthesis of polymeric systems, which allows for controlled release of pesticides for a prolonged period of time. Herein we report the synthesis and characterization of novel potentially bioactive (co)oligoesters with bioactive moieties (selected from pesticides) which are covalently linked along an oligoester backbone.

METHODS

The delivery systems of pesticides were prepared via anionic ring-opening polymerization of β-substituted β-lactones containing bioactive moieties as a pendant group selected from pesticides and their copolymerization with β-butyrolactone in the presence of carboxylates as initiators. Electrospray ionization multistage mass spectrometry (ESI-MS(n)) supported by (1)H NMR were applied in order to establish the structure, at a molecular level, of the new biodegradable oligomeric release system of selected pesticides.

RESULTS

Based on ESI-MS(n) analyses, the structures of the resulting (co)oligoesters were established at the molecular level. The ESI-MS/MS allowed to confirm the structures of end groups and to determine the composition of individual (co)oligoester molecules which contained one, two or three bioactive molecules per (co)oligomer. Additionally, it was shown that fragmentation of selected ions of potentially bioactive (co)oligoesters proceeded via random breakage of ester bonds along the oligomer chain and ester bonds of the bioactive pendant group.

CONCLUSIONS

An analytical method for detailed structural characterization at the molecular level of potentially bioactive (co)oligoesters has been developed. These results are important in the analysis of designed biodegradable polymeric controlled-release systems of pesticides with potential agricultural applications.

Transesterification of PHA to oligomers covalently bonded with (bio)active compounds containing either carboxyl or hydroxyl functionalities

This manuscript presents the synthesis and structural characterisation of novel biodegradable polymeric controlled-release systems of pesticides with potentially higher resistance to weather conditions in comparison to conventional forms of pesticides. Two methods for the preparation of pesticide-oligomer conjugates using the transesterification reaction were developed. The first method of obtaining conjugates, which consist of bioactive compounds with the carboxyl group and polyhydroxyalkanoates (PHAs) oligomers, is "one-pot" transesterification. In the second method, conjugates of bioactive compounds with hydroxyl group and polyhydroxyalkanoates oligomers were obtained in two-step method, through cyclic poly(3-hydroxybutyrate) oligomers. The obtained pesticide-PHA conjugates were comprehensively characterised using GPC, 1H NMR and mass spectrometry techniques. The structural characterisation of the obtained products at the molecular level with the aid of mass spectrometry confirmed that both of the synthetic strategies employed led to the formation of conjugates in which selected pesticides were covalently bonded to PHA oligomers via a hydrolysable ester bond.

Molecular level structure of novel synthetic analogues of aliphatic biopolyesters as revealed by multistage mass spectrometry

The present study focuses on electrospray ionisation (ESI) tandem mass spectrometry of novel copolyesters obtained by anionic ring-opening copolymerisation of β-substituted β-lactones. Detailed analysis of these copolyesters, including molecular chain architecture as well as the structures of the end groups, was performed using ESI-MS/MS collision-induced dissociation spectra. The random arrangement of comonomeric units along the copolyester chains was demonstrated by comparison of ESI-MS(n) fragmentation spectra and fragmentation pathways. Sequence distribution analysis of comonomeric units confirmed the copolymer's random structure. ESI-MS(n) proved to be a promising technique for structural analysis of copolyesters obtained via anionic ROP.

Selective reduction of PHA biopolyesters and their synthetic analogues to corresponding PHA oligodiols proved by structural studies

A highly selective method is described for controlling the degradation of polyhydroxyalkanoates, PHA, via a reduction reaction that uses lithium borohydride. Using this method, oligo(hydroxyalkanoate)diols derived from a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) biopolyester [poly(3HB-co-4HB)] and from synthetic atactic poly[(R,S)-3-hydroxybutyrate] (a-PHB) were obtained. The structural characterization of the oligo(hydroxyalkanoate)diols was conducted using NMR and ESI-mass spectrometry analyses, which confirmed that oligomers that were terminated by two hydroxyl end groups were formed. The reduction of the ester groups occurred in a statistical way regardless of the chemical structure of the comonomer units or of the microstructure of the polyester chain. The presented method can be used to synthesize various PHA oligodiols that are potentially useful in the further synthesis of tailor-made biodegradable materials.

Electrospray ionisation mass spectrometry molecular-level structural characterisation of novel phenoxycarboxylic acid-oligo(3-hydroxybutyrate) conjugates with potential agricultural applications

RATIONALE

Due to the low resistance of forms of pesticides to environmental conditions, agrochemicals frequently do not reach their objective, which may cause environmental pollution. The minimisation of the adverse effects of pesticides requires the development of a system for their long-term controlled release. In the present work, we report the synthesis and structural studies of novel controlled-release pesticide-oligo-3-hydroxybutyrate systems with potential agricultural applications.

METHODS

The novel controlled-release pesticide-oligo(3-hydroxybutyrate) systems were obtained via the anionic ring-opening oligomerisation of (R,S)-β-butyrolactone initiated by the potassium salt of selected pesticides. Electrospray ionisation mass spectrometry (ESI-MS(n)) analyses in positive-ion mode, supported by (1)H NMR results, were used for the structural characterisation of the obtained conjugates. The presence of the respective pesticides in an unchanged form associated with oligo-3-hydroxybutyrate chains was confirmed by ESI-MS/MS experiments performed for selected pesticide-oligo(3-hydroxybutyrate) ions and by the subsequent investigation of their fragmentation pathways.

RESULTS

The structures of the resulting conjugates were established at the molecular level with the aid of ESI-MS(n). The presence of one and two chlorine atoms (derived from MCPA and 2,4-D pesticides) in the conjugates studied was confirmed by comparison of the calculated and experimental isotopic profiles for the selected ions of the respective conjugates. The fragmentation of the selected ions of the resulting conjugates confirmed that the respective pesticides are covalently bonded with oligo(3-hydroxybutyrate) through a hydrolysable ester bond.

CONCLUSIONS

An analytical method has been developed for the characterisation of new pesticide-oligo(3-hydroxybutyrate) conjugates. A detailed NMR and MS structural characterisation of the designed controlled-release system of the pesticides was performed. These results are important in the analysis of designed biodegradable polymeric conjugates with potential agricultural applications.

Paraneoplastic Vitelliform Retinopathy Associated with Cutaneous or Uveal Melanoma and Metastases

PURPOSE

To report unusual vitelliform fundus findings in three cases of paraneoplastic retinopathy associated with metastasised cutaneous or uveal melanoma and in one case, a unique immunoreactivity response.

PATIENTS AND METHODS

Observational case series. The histories of three patients with MAR-like paraneoplastic retinopathy were reviewed. Electroretinography, Goldmann perimetry, fluorescein angiography, and in one case optical coherence tomography, immunohistochemistry and Western blotting were performed.

RESULTS

All patients revealed similar paraneoplastic vitelliform retinal abnormalities. Symptoms in two cases differed from the classical MAR syndrome. In one case, western blotting and immunohistochemistry demonstrated antibodies against 120-kDa, a soluble photoreceptor protein. No immunoreactivity to retinal bipolar cells was detected.

CONCLUSION

The clinical, electrophysiological, and immunological findings in our patients suggest a melanoma associated paraneoplastic origin, like in MAR syndrome. However contrary to MAR syndrome, this paraneoplastic vitelliform retinopathy exhibits a peculiar fundus picture, consisting of serous macular detachment and nummular vitelliform lesions in the posterior pole. This could be an unusual presentation of MAR or a separate paraneoplastic entity.

Synthesis of poly(2-methyl-3-hydroxyoctanoate) via anionic polymerization of alpha-methyl-beta-pentyl-beta-propiolactone

Synthesis of an alpha,beta-alkyl branched polyester, i.e., poly(2-methyl-3-hydroxyoctanoate), has been accomplished via anionic polymerization of alpha-methyl-beta-pentyl-beta-propiolactone mediated by supramolecular complexes of potassium methoxide or potassium hydroxide, respectively. The structure of resulting polymers has been established by electrospray ionization multistage mass spectrometry (ESI-MSn), FT-IR, NMR, and GPC analyses. Previously proposed addition-elimination mechanism of the polymerization of beta-lactones containing alpha-hydrogen by alkoxide anion has been confirmed to operate also in the case of beta-lactone having alkyl substituents in both alpha and beta positions.

Water-soluble L-alanine and related oligopeptide conjugates with poly[(R,S)-3-hydroxybutanoic acid] oligomers, synthesis and structural studies by means of electrospray ionization multistage mass spectrometry

The reactions of (R,S) beta-butyrolactone with L-alanine and related oligopeptides (Ala-Ala-Ala) were investigated. The resulting water-soluble oligomers were composed of poly[(R,S)-3-hydroxybutanoic acid] (a-PHB) covalently conjugated to L-alanine and Ala-Ala-Ala oligopeptide. The other chain end was of the carboxylic acid type. The structure of the obtained oligomers was assessed by electrospray ionization multistage mass spectrometry (ESI-MSn) and the respective structural information was completed by IR, NMR, and GPC analyses. The molecular weight and structure of the products could be controlled through reaction conditions. Using this new synthetic approach. a-PHB oligomers with well-defined end groups, as well as respective block copolymers, can be prepared via regioselective ring-opening oligomerization of (R,S) beta-butyrolactone induced by amino acids under their zwitterionic form.

Expression of CC chemokines and their receptors in the eye in autoimmune anterior uveitis associated with EAE

PURPOSE

To determine the pattern of expression of CC chemokines and their receptors in the eyes of Lewis rats and to establish their role in autoimmune anterior uveitis (AU) associated with experimental autoimmune encephalomyelitis (EAE).

METHODS

EAE/AU was induced in Lewis rats with myelin basic protein in complete Freund's adjuvant (CFA). The rats were scored for the development of clinical EAE and AU. The expression of CCL5/regulated on activation normal T-cell expressed and secreted (RANTES), CCL2/monocyte chemotactic protein (MCP)-1, CCL3/macrophage inflammatory protein (MIP)-1alpha, and CCL4/MIP-1beta and their receptors was examined at the preclinical stage, onset, peak, and recovery by RT-PCR and ELISA. EAE/AU rats were treated with neutralizing polyclonal antibodies against CCL3/MIP-1alpha, CCL4/MIP-1beta, CCL2/MCP-1, and CCL5/RANTES and tested for the suppression of onset of clinical AU and EAE. The control group received normal rabbit IgG at the same dose.

RESULTS

The gene expression of those chemokines was upregulated concurrently with symptom onset of EAE/AU and correlated with the intensity of inflammatory changes in the eye and central nervous system (CNS). The highest expression of CCL4/RANTES, CCL2/MCP-1, and CCL3/MIP-1alpha in the eye was detected at onset of clinical uveitis, whereas CCL4/MIP-1beta was elevated at the peak of AU. The expression of chemokine receptors associated with T-helper (Th)1-type response, CCR1 and CCR5, correlated with their appropriate ligands and was the highest at the peak of AU, whereas CCR2, the receptor for CCL2/MCP-1, was present before the onset of the disease. Treatment of anti-MIP-1beta and anti-MCP-1 significantly delayed the onset and shortened the duration of AU and EAE. Anti-MIP-1alpha treatment had no effect on clinical EAE but inhibited the clinical signs of AU. Although CCL5/RANTES expression was observed during the entire course of the disease, anti-RANTES treatment had no effect on clinical disease progression.

CONCLUSIONS

The data suggest that CCL2/MCP-1, CCL3/MIP-1alpha, and CCL4/MIP-beta contribute to the recruitment of inflammatory cells into the eye and CNS and to disease activity.

A new type of thermoalkalophilic hydrolase of Paucimonas lemoignei with high specificity for amorphous polyesters of short chain-length hydroxyalkanoic acids

A novel type of hydrolase was purified from culture fluid of Paucimonas (formerly Pseudomonas) lemoignei. Biochemical characterization revealed an unusual substrate specificity of the purified enzyme for amorphous poly((R)-3-hydroxyalkanoates) (PHA) such as native granules of natural poly((R)-3-hydroxybutyrate) (PHB) or poly((R)-3-hydroxyvalerate) (PHV), artificial cholate-coated granules of natural PHB or PHV, atactic poly((R,S)-3-hydroxybutyrate), and oligomers of (R)-3-hydroxybutyrate (3HB) with six or more 3HB units. The enzyme has the unique property to recognize the physical state of the polymeric substrate by discrimination between amorphous PHA (good substrate) and denatured, partially crystalline PHA (no substrate). The pentamers of 3HB or 3HV were identified as the main products of enzymatic hydrolysis of native PHB or PHV, respectively. No activity was found with any denatured PHA, oligomers of (R)-3HB with five or less 3HB units, poly(6-hydroxyhexanoate), substrates of lipases such as tributyrin or triolein, substrates for amidases/nitrilases, DNA, RNA, casein, N-alpha-benzoyl-l-arginine-4-nitranilide, or starch. The purified enzyme (M(r) 36,209) was remarkably stable and active at high temperature (60 degrees C), high pH (up to 12.0), low ionic strength (distilled water), and in solvents (e.g. n-propyl alcohol). The depolymerase contained no essential SH groups or essential disulfide bridges and was insensitive to high concentrations of ionic (SDS) and nonionic (Triton and Tween) detergents. Characterization of the cloned structural gene (phaZ7) and the DNA-deduced amino acid sequence revealed no homologies to any PHB depolymerase or any other sequence of data banks except for a short sequence related to the active site serine of serine hydrolases. A classification of the enzyme into a new family (family 9) of carboxyesterases (Arpigny, J. L., and Jaeger, K.-E. (1999) Biochem. J. 343, 177-183) is suggested.

Retinal anti-bipolar cell antibodies in a patient with paraneoplastic retinopathy and colon carcinoma

PURPOSE

To describe clinical, electrophysiologic, and immunologic features of a unique paraneoplastic retinopathy with characteristics of cancer-associated and melanoma-associated retinopathy.

METHODS

Serial assessment of clinical visual function, electroretinography, and assays of anti-retinal antibodies.

RESULTS

A 51-year-old woman with progressive visual glare for 1 year had normal visual acuity and color vision, paracentral scotomas, and a normal-appearing retina. Electroretinography revealed no responses of the right eye and attenuated responses of the left eye, especially those recorded under scotopic conditions. Anti-bipolar antibodies were detected. Subsequent evaluation uncovered adenocarcinoma of the colon. Several months after resection of the tumor and chemotherapy, no evidence existed of cancer or anti-bipolar cell antibodies, and electroretinography responses were markedly improved.

CONCLUSION

The presence of anti-bipolar cell antibodies in a patient with retinal dysfunction is not specific of melanoma-associated retinopathy. Effective treatment of cancer may result in elimination of associated anti-retinal antibodies and improved retinal function.

Biomimetic polyesters and their role in ion transport across cell membranes

Syntheses of biomimetic low-molecular weight poly-(R)-3-hydroxybutanoate mediated by three types of supramolecular catalysts are presented. The utility of these synthetic polyesters for preparation of artificial channels in phospholipid bilayers capable of sodium and calcium ion transport across cell membranes, is discussed. Further studies on possible applications of these bio-polymers for manufacturing drugs of prolonged activity are under way.

Importance of cryptic myelin basic protein epitopes in the pathogenicity of acute and recurrent anterior uveitis associated with EAE

Lewis rats immunized with myelin basic protein (MBP) develop experimental autoimmune encephalomyelitis (EAE) and associated anterior uveitis (AU), which can relapse without recurring of EAE. In this study, we analyzed the repertoire of MBP epitopes that play a role in acute and recurrent AU by injection of MBP synthetic peptides. In addition to the encephalitogenic epitopes 69-89 and 87-99, several cryptic epitopes were found to be strongly uveitogenic in Lewis rats upon immunization with synthetic peptides, including 100-120, 121-140 and 142-167. However, the peptide corresponding to the MBP residues 1-20 was uniquely capable of inducing AU without EAE. Immunization with intact MBP was not essential for the induction of the recurrence of AU. The responses of T cells from lymph nodes and spleens showed a dominant response to the original disease-induced epitope with responses to secondary epitopes. In conclusion, the analysis of pathogenic determinants important for the induction of uveitis provides further evidence that MBP-specific T cells also contribute to the pathogenesis of anterior uveitis. Moreover, this also suggests that a distinct immunoregulatory mechanism exists in the eye and spinal cord because of the uniqueness of the epitope 1-20 in AU but not EAE, and the capability of MBP-specific T cells of inducing AU without EAE.

Epitope recognition and T cell receptors in recurrent autoimmune anterior uveitis in Lewis rats immunized with myelin basic protein

Lewis rats immunized with myelin basic protein (MBP) develop experimental autoimmune encephalomyelitis (EAE) and associated anterior uveitis (AU). Rats recover and become resistant to further reinduction of EAE. We investigated whether the resistance to reinduction of EAE was associated with the resistance to AU in LEW rats reinjected with MBP. We demonstrated that while rats remained resistant to EAE, they become susceptible to uveitis after recovery, and suffered a second episode of disease. The susceptibility to reinduced disease was associated with the recognition of new MBP epitopes. In contrast to the initial episode of AU, TCR Vbeta8.2 predominance was not observed in the iris/ciliary body. Our results suggest that T cells specific for MBP, which are rapidly reactivated when re-exposed to antigen, are sufficient to induce clinical uveitis in LEW rats. This process may involve a shifting of T cell specificity from the major encephalitogenic peptide utilizing the Vbeta8.2 receptor to a more diverse cell repertoire.

The role of T cells in autoimmune uveitis

Autoimmune diseases result from the activation of self-reactive T cells recognizing autoantigens or foreign antigens cross-reactive with an autoantigen. T cells are thought to play a major role in autoimmune diseases in different organs, including the eye. This review focuses on the role of T cells in autoimmune uveitis in humans and in animal models of experimental autoimmune uveitis. Since rheumatoid arthritis is an autoimmune disease that has been studied far more extensively than uveitis, we have also included a review of clinical and experimental observations relevant to that disease.

Biomimetic polyesters and their role in ion transport across cell membranes

Syntheses of biomimetic low-molecular weight poly-(R)-3-hydroxybutanoate mediated by three types of supramolecular catalysts are presented. The utility of these synthetic polyesters for preparation of artificial channels in phospholipid bilayers capable of sodium and calcium ion transport across cell membranes, is discussed. Further studies on possible applications of these bio-polymers for manufacturing drugs of prolonged activity are under way.

Electrospray multistep ion trap mass spectrometry for the structural characterisation of poly

Electrospray 'soft' ionisation (ESI) and multistep mass spectrometry (MS(n)) techniques enable characterisation of a bioactive polymer, poly[(R,S)-3-hydroxybutanoic acid] (a-PHB), containing covalently bonded benzylpenicillin. The chemical structures of individual mass-selected bioactive macromolecules have been determined, and their fragmentation mechanisms have been compared with those of pure penicillin G. Copyright 2000 John Wiley & Sons, Ltd.

Novel synthesis of functionalized poly(3-hydroxybutanoic acid) and its copolymers

Novel feasibility of fuctionalized poly(3-hydroxybutanoic acid), PHB, and its copolymers synthesis via ring-opening of beta-butyrolactone (ROP) mediated by activated anionic initiators or enzymes in vitro is presented. Using these new synthetic approaches, PHB with defined chemical structure of the end groups as well as block, graft and random copolymers have been obtained and characterized by IR, NMR, ESI-MS and GPC techniques. The relationship between the structure and properties of the novel polymeric materials prepared is discussed.

Electrospray ionisation tandem mass spectrometry of poly

Evaluation of polymer end-capping reactions with the aid of electrospray ionisation tandem mass spectrometry techniques (ESI-MS(n)) allows characterisation of novel poly[(R, S)-3-hydroxybutanoic acid]-(a-PHB) telechelics, containing primary hydroxyl groups at both polymer chain ends. The chemical structures of individual mass-selected macromolecules of the well-defined a-PHB telechelics have been defined in this way, and fragmentation mechanisms have been proposed. Copyright 1999 John Wiley & Sons, Ltd.