Modification of Poly(lactic acid) by the Plasticization for Application in the Packaging Industry

Plastic products, especially in the packaging industry, have become the main commodities penetrating virtually every aspect of our lives. Unfortunately, their omnipresence is not neutral to the natural environment. Pollution in the form of microplastics is a global problem. Therefore, green technologies that enter into the circular economy become an important topic. As part of the research work, the modification of poly(lactic acid) has been studied for use in the packaging industry. Due to its intrinsic rigidity, plasticizing substances had to be introduced in PLA in order to improve its plastic deformability. Both high-molecular compounds such as ethoxylated lauryl alcohol, block copolymer of ethylene oxide and propylene oxide, and ethoxylated stearic acid as well as low-molecular compounds such as di-2-ethylhexyl adipate, di-2-ethylhexyl sebacate, and triethyl citrate were used. The samples extruded from plasticized polymers were characterized using differential scanning calorimetry, thermal gravimetric analysis, and mechanical properties including Young’s modulus. The melt flow rate (MFR) and molar mass distribution were determined. For all modified samples the glass transition temperature, depending on the plasticizer used, was shifted towards lower values compared to the base polymer. The best result was obtained for di-2-ethylhexyl adipate (ADO) and di-2-ethylhexyl sebacate (SDO). The elongation at break increased significantly for ADO at about 21%. The highest elongation was obtained for SDO (about 35%), although it obtained a higher glass temperature. The degradation of the polymer was not observed for both plasticizers. For these plasticizers (ADO and SDO) it also lowered Young’s module by about 26%, and at the infrared spectrum deformation of peaks were observed, which may indicate the interaction of the ester carbonyl group of PLA with plasticizers. Therefore it can be concluded that they are good modifiers. The selected plasticizers that are used in the production of food contact materials, in particular in the production of PVC (polyvinyl chloride) food films, also exhibited great potential to be applied to PLA food films, and exhibit better properties than the citrate, which are indicated in many publications as PLA plasticizers.

R/G Value-A Numeric Index of Individual Periodontal Health and Oral Microbiome Dynamics

The dysbiosis of oral microbiome (OM) precedes the clinical signs of periodontal disease. Its simple measure thus could indicate individuals at risk of periodontitis development; however, such a tool is still missing. Up to now, numerous microbial taxa were associated with periodontal health or periodontitis. The outputs of most studies could, nevertheless, be slightly biased from following two reasons: First, the healthy group is often characterized only by the absence of the disease, but the individuals could already suffer from dysbiosis without any visible signs. Second, the healthy/diseased OM characteristics are frequently determined based on average data obtained for whole groups of periodontally healthy persons versus patients. Especially in smaller sets of tested individuals the typical individual variability can thus complicate the unambiguous assignment of oral taxa to respective state of health. In this work the taxonomic composition of OM was evaluated for 20 periodontally healthy individuals and 15 patients with chronic periodontitis. The narrowed selection set of the most diseased patients (confirmed by clinical parameters) and the most distant group of healthy individuals with the lowest probability of dysbiosis was determined by clustering analysis and used for identification of marker taxa. Based on their representation in each individual oral cavity we proposed the numeric index of periodontal health called R/G value. Its diagnostic potential was further confirmed using independent set of 20 periodontally healthy individuals and 20 patients with periodontitis with 95 percent of samples assigned correctly. We also assessed the individual temporal OM dynamics in periodontal health and we compared it to periodontitis. We revealed that the taxonomic composition of the system changes dynamically but generally it ranges within values typical for periodontal health or transient state, but far from values typical for periodontitis. R/G value tool, formulated from individually evaluated data, allowed us to arrange individual OMs into a continuous series, instead of two distinct groups, thus mimicking the gradual transformation of a virtual person from periodontal health to disease. The application of R/G value index thus represents a very promising diagnostic tool for early prediction of persons at risk of developing periodontal disease.

Retention Mechanism of Branched Macromolecules in Size Exclusion Chromatography

The theory of Stockmayer in the modifications of Thurmond and Zimm has been used for the description of the size exclusion chromatography separation of randomly branched molecules with tetrafunctional branch points. It is assumed that free chain ends, created by the branching process, cause the molecules to be entrapped in the pores of the column packing with the time of their release given by the exponential law characteristic for the monomolecular reactions. Using this assumption, the anomalous elution behavior of such molecules can be modeled. With increasing elution volume, the average values of radius of gyration and, to a lesser degree, of molecular weight decrease and, after passing a minimum, again increase in the low-molecular weight region.

Getting Closer to Absolute Molar Masses of Technical Lignins

Determination of molecular weight parameters of native and, in particular, technical lignins are based on size exclusion chromatography (SEC) approaches. However, no matter which approach is used, either conventional SEC with a refractive index detector and calibration with standards or multi-angle light scattering (MALS) detection at 488 nm, 633 nm, 658 nm, or 690 nm, all variants can be severely erroneous. The lack of calibration standards with high structural similarity to lignin impairs the quality of the molar masses determined by conventional SEC, and the typical fluorescence of (technical) lignins renders the corresponding MALS data rather questionable. Application of MALS detection at 785 nm by using an infrared laser largely overcomes those problems and allows for a reliable and reproducible determination of the molar mass distributions of all types of lignins, which has been demonstrated in this study for various and structurally different analytes, such as kraft lignins, milled-wood lignin, lignosulfonates, and biorefinery lignins. The topics of calibration, lignin fluorescence, and lignin UV absorption in connection with MALS detection are critically discussed in detail, and a reliable protocol is presented. Correction factors based on MALS measurements have been determined for commercially available calibration standards, such as pullulan and polystyrene sulfonate, so that now more reliable mass data can be obtained also if no MALS system is available and these conventional calibration standards have to be resorted to.

C-reactive protein in patients with aggressive periodontitis

BACKGROUND/PURPOSE

The aim of this study was to evaluate and compare the systemic levels of C-reactive protein (CRP) in peripheral blood samples of patients with aggressive periodontitis during the first twelve months of periodontal treatment, at exactly six month interval measurements, and compare them with clinical periodontal parameters.

MATERIALS AND METHODS

All patients (N = 45) were examined prior to the initiation of periodontal treatment. Patients were divided into two groups GAgP (Generalised form of aggressive periodontitis, N = 23) and group LAgP (Localised form of aggressive periodontitis, N = 22). Control group (CON) included 60 individuals with healthy periodontium. The levels of CRP were determined in both groups GAgP and LAgP three times in 6 month intervals during the periodontal treatment.

RESULTS

CRP is a plasma protein that reflects the extent of the acute phase response to inflammation and is one of the markers of choice for monitoring this response. In our study, CRP levels decreased in course of periodontal treatment in both groups (GAgP and LAgP) in a similar way as bleeding on probing (BOP) and probing pocket depth (PPD) indices.

CONCLUSION

Our study results showed that CRP levels, as well as bleeding on probing (BOP) and probing pocket depth (PPD), indices decreased in course of periodontal treatment in patients with generalised and localised aggressive periodontitis. Therefore this marker might be exploitable as a means to evaluate periodontal health in patients with aggressive periodontitis.

Low-Level Laser Therapy After Wisdom Teeth Surgery: Evaluation of Immunologic Markers (Secretory Immunoglobulin A and Lysozyme Levels) and Thermographic Examination: Placebo Controlled Study

OBJECTIVE

The goal of this investigation is to analyze the effect of therapeutic low-level laser therapy (LLLT) to have a possibility to check pain and inflammation connected with surgical removal of impacted lower third molars in general anesthesia or even phobia [not accompanied by pain or fear of dental treatment, using immunologic markers-secretory immunoglobulin A (sIgA) and lysozyme]. The healing process was also monitored by infrared thermography.

BACKGROUND DATA

LLLT can accelerate the proliferation phase of healing and decrease the inflammatory reaction, but the effect is not really clear.

MATERIALS AND METHODS

The treatment group comprised 213 impacted third molars (144 laser group and 74 placebo group). Laser radiation (diode laser 830 nm) was applied. The effectivity of laser therapy was evaluated based on immunological tests, that is, before and after treatment with sIgA and lysozyme in nonstimulated saliva. Thermographic examination was performed by infrared camera.

RESULTS

After laser irradiation, the sIgA decreases from 546.91 mg/L (SD 354.58) to 304.91 mg/L (SD 191.96), and in the control group from 602.25 mg/L (SD 343.62) to 425.62 mg/L (SD 220.51); the differences were significant, the lysozyme value being lower. After laser therapy, the laser and placebo sides in the area of the third molars were differed in 0.2°C.

CONCLUSIONS

The 830 nm wavelength penetrates to deep-seated tissues. A positive association was found between concentration of salivary sIgA and lysozyme in the saliva after LLLT application. The deep-seated wounds after wisdom teeth extraction had no effect on temperature rise in the face.

Enhanced multiparametric hyaluronan degradation for production of molar-mass-defined fragments

Hyaluronic acid (HA) is known to serve as a dynamic mediator intervening in many physiological functions. Its specific effect has been repeatedly confirmed to be strongly influenced by the molecular size of hyaluronan fragments. However common technological approaches of HA fragments production have their limitations. In many cases, the final products do not meet the strict pharmaceutical requirements, specifically due to size polydispersity and reaction contaminants. We present novel methodology based on combination of unique incidental ability of the plant-derived protease papain to split the glycosidic bonds and an indispensable advantages of biocompatible macroporous material with incorporated ferrous ions serving as carrier for covalent papain fixation. This atypical and yet unpublished highly efficient multiparametric approach allows enhanced HA fragmentation for easily and safely producing molar-mass-defined HA fragments with narrow size distribution. Native polyacrylamide gel electrophoresis (PAGE) and size exclusion chromatography/multi-angle light scattering (SEC-MALS) confirmed the effectiveness of our multiparametric approach.

Periodontitis as a risk factor of atherosclerosis

Over the last two decades, the amount of evidence corroborating an association between dental plaque bacteria and coronary diseases that develop as a result of atherosclerosis has increased. These findings have brought a new aspect to the etiology of the disease. There are several mechanisms by which dental plaque bacteria may initiate or worsen atherosclerotic processes: activation of innate immunity, bacteremia related to dental treatment, and direct involvement of mediators activated by dental plaque and involvement of cytokines and heat shock proteins from dental plaque bacteria. There are common predisposing factors which influence both periodontitis and atherosclerosis. Both diseases can be initiated in early childhood, although the first symptoms may not appear until adulthood. The formation of lipid stripes has been reported in 10-year-old children and the increased prevalence of obesity in children and adolescents is a risk factor contributing to lipid stripes development. Endothelium damage caused by the formation of lipid stripes in early childhood may lead to bacteria penetrating into blood circulation after oral cavity procedures for children as well as for patients with aggressive and chronic periodontitis.

Immune markers in oral discomfort patients before and after elimination of oral galvanism

BACKGROUND

An enhanced release of metals in the mouth due to galvanic cell formation is considered to be one of the causes of oral discomfort. The aim of this study was to investigate the influence of galvanic cell on salivary immune defense factors.

MATERIAL AND METHODS

The levels of IgA1, IgA2, sIgA, lysozyme and antiIgA/HSP60 were evaluated in representative samples from 159 patients with galvanism, from 177 patients without galvanism and in two control groups. All the participants underwent personal history taking, clinical examination, galvanic currents measurement and saliva collection.

RESULTS

Electro active dental materials were removed in 30 patients. There was a significant increase in IgA2 level, a significant decrease in antiIgA/HSP60 levels and an increase in IgA1, sIgA and lysozyme levels found after the removal of electro active restorations. Morphological symptoms disappeared in 70% of the treated patients.

CONCLUSION

The study confirmed that pathologic galvanic phenomena influences the immune defense reactions in the oral cavity and thus may cause the symptoms of oral discomfort. A measurement of the galvanism and a subsequent removal of electro active restorations should become a common therapeutic procedure in the patients with oral discomfort.

Influence of metals on cytokines production in connection with successful implantation therapy in dentistry

OBJECTIVES

In most of patients in need of implantation treatment in the oral cavity, implants heal well, nevertheless, there are some individuals, in whom titanium implants fail for reasons, which remain unclear.

DESIGN

The aim of our study was to determine if there is a difference between metal influenced IL-1β, IL-4, IL-6, TNF-α and IFN-γ cytokines production in patients with successfully healed implants compared to those, whose implant therapy was unsuccessful.

SETTING

The two study groups included 12 patients with failed dental titanium implants and 9 patients with successfully healed implants. In the subjects, cytokine production was established after lymphocyte cultivation with mercury, nickel and titanium antigens.

RESULTS

IL-1β levels were significantly increased in all patients after stimulation with titanium and in patients with accepted implants compared to patients with failed implants after the stimulation with mercury and titanium. Titanium caused significantly increased IL-6 production in all patients. TNF-α and IFN-γ levels were also significantly increased after the stimulation with titanium. Significantly increased TNF-α levels were found in patients with accepted implants as compared to patients with failed implants.

CONCLUSIONS

Increased production of IL-1β a IL-6 cytokines in reaction to titanium and increased production of TNF-α and IFN-γ cytokines in reaction to mercury, which is very often present in the form of amalgam in the oral cavity of persons in need of implant therapy, can play an important role in immune reactions during implant healing process. In patients with failed titanium implants, decreased production of these cytokines may participate in implant failure.

The influence of galvanic currents and voltage on the proliferation activity of lymphocytes and expression of cell surface molecules

Release of metal ions from dental metal fillings supported by galvanism can cause local or general pathological problems in sensitive and genetically susceptible individuals. We aimed to investigate in vitro lymphocyte responses and expression of surface molecules influenced by galvanic currents and voltage. Human peripheral blood lymphocytes were influenced by galvanic currents and voltages and lymphocyte proliferation was measured. Control samples were not exposed to the influence of galvanism. We also studied the expression of surface molecules by the FACS analysis. A 15-h and shorter influence of almost all tested currents and voltages caused a significant decrease in lymphocyte proliferation and the 15-h influence of 20 microA currents significantly increased expression of surface molecules CD 19, 11a/18, 19/69 and 19/95. An influence of 10 and 3 microA currents led to a significant decrease in the expression of surface molecules CD 3, 11a/18, 3/69 and 3/95 and to a significant increase in CD 19 expression. An 80 mV voltage influence led to a significant decrease in the expression of surface molecules CD 3, 11a/18, 3/69, 3/95, 19/69 and 19/95, and 200 and 300 mV voltages significantly decreased the expression of surface molecules CD 3, 19, 11a/18, 3/95 and 19/95 and significantly increased CD 19/69 expression. A long-lasting influence of galvanism can, in sensitive and genetically susceptible individuals, influence lymphocyte proliferation and surface molecule expression. The threshold for pathological values of 5 microA for galvanic currents and 100 mV for galvanic voltage was confirmed.

Sensitization to inorganic mercury could be a risk factor for infertility

INTRODUCTION

Heavy metals can negatively influence the reproduction due to the fact that they are able to impair the immune reactions including autoantibody production in susceptible individuals. In such a way the infertility could be also caused by altered pathologic immune reaction.

AIM OF THE STUDY

To investigate the in vitro lymphocyte reaction after stimulation with metals and production of gamma interferon and antisperm antibodies in supernatants after lymphocyte stimulation in patients with infertility and with proven antisperm antibodies in their serum. The cause of antisperm antibodies presence was not determined.

METHODS

The diagnosis of metal allergy was performed by the lymphocyte proliferation method modified for metals (MELISA) in supernatants of tissue cultures of lymphocytes without the antigen stimulation and after stimulation with mercury chloride, the in vitro production of gamma interferon and antisperm antibodies was studied by ELISA.

RESULTS

More than 50% of patients were reacting to mercury, iron, aluminium and silver as mean by lymphocyte reactivity. When compared the lymphocyte reaction in patients with and without mercury allergy we found that the lymphocytes of patients with mercury intolerance produced less gamma interferon and more antisperm antibodies in supernatants after mercury stimulation of their lymphocytes.

CONCLUSION

In patients with metal intolerance diagnosed by the MELISA test the release of metal ions from dental materials can be one of the stimulating factors which may adversely affect fertility.

[Effect of heavy metals on immune reactions in patients with infertility]

BACKGROUND

Heavy metals can negatively influence reproduction because in sensitive persons they are able to alter the immune reactions including autoantibodies production. The altered immune reaction can then cause infertility.

METHODS AND RESULTS

The in vitro lymphocyte reaction after stimulation with metals, the production of interferon (IFN-gamma) and antisperm antibodies in supernatants after lymphocyte stimulation in patients with infertility and with the antisperm antibodies present in their serum were investigated. The cause of antisperm antibodies presence was not determined. The diagnosis of metal intolerance was performed by the proliferation method modified for metals (Melisa). In supernatants of tissue cultures of lymphocytes without the antigen stimulation and after stimulation with mercury chloride, the in vitro production of gamma interferon and antisperm antibodies was studied by Elisa. More than 50% of patients did not tolerate mercury, iron, aluminium and silver. When the lymphocyte reaction was compared in patients with and without mercury intolerance we found that lymphocytes of patients with mercury intolerance produced less gamma interferon and more antisperm antibodies in supernatants after mercury stimulation of lymphocytes.

CONCLUSIONS

In patients with metal intolerance diagnosed by the Melisa test, metal ions released from the dental materials can represent a factor, that does not cause infertility but is able to influence it negatively.

[Sperm antibodies and immunologic intolerance to metals in infertile couples]

OBJECTIVE

Verification of the hypothesis of a relationship between the presence of antibodies against sperm cells and immunological reactivity to some metals in infertile couples by the MELISA test.

SETTING

Department of Obstetrics and Gynecology, Medical Faculty, Charles University and Faculty Hospital, Plzen.

METHOD

From 23 female patients and 21 men (a total of 44 subjects treated for infertility) with confirmed serum antibodies against sperm cells the authors isolated lymphocytyes from the peripheral blood stream, divided them into individual cultures and investigated them by the MELISA test using different metal compounds.

RESULTS

The outcome of the MELISA test are values of the stimulation index (SI) by means of which the authors investigated the reactivity of the organism to the given metal. Special attention was devoted to compounds of organic and inorganic mercury. The SI values were subsequently compared with different data obtained from a detailed anamnestic questionnaire which was focused specially on contact with metals and on allergic reactions. In the investigated group of patients the authors detected a positive immune reactivity to inorganic mercury, Ag, Al, Fe. In some subjects they found a very high positive immune reactivity to inorganic mercury, Ni, Al, Cd and Ti. The control groups were formed by healthy fertile subjects without antibodies against sperm cells and with physiological SI values.

CONCLUSION

The authors did not prove a direct relationship between the intensity of the laboratory reactivity to metals and the presence of antibodies against sperm cells which cause deterioration of fertility. An exogenous load of metals could in case of genetic predisposition be only one of the factors which participate in the formation of antibodies against sperm cells. The investigation proved that its is not essential, contrary to the view of many stomatologists, to eliminate metal compounds completely from dental practice.

Estimation of width of narrow molecular-weight distributions by size-exclusion chromatography with concentration and light scattering detection

A new method for the estimation of the weight-to-number-average molecular-weight ratio, Mw/Mn of polymers with a narrow molecular-weight distribution, approximated by log-normal distribution, is proposed using size-exclusion chromatography (SEC) with concentration and light-scattering detectors. From experimental data, the Mw/Mn ratios are calculated by two procedures: one using the concentration and light-scattering elution curve for the polymer measured, and the other based on the concentration elution curve and calibration line for a wide range of molecular masses. An iteration method has been developed making the two Mw/Mn ratios converge. The method was applied to a series of narrow molecular-weight distribution polystyrene standards.