Polyelectrolytes

The number of nosocomial infections related to
implants and medical devices increase alarmingly worldwide.
New strategies based on the design of antimicrobial coatings
are required to prevent such infections. Polyelectrolyte
“multilayer” films constitute a powerful tool for nanoscale
surface functionalization which allows addressing this issue. By
investigating films built up with poly(arginine) (PAR) of
various chain lengths (10, 30, 100, and 200 residues) and
hyaluronic acid (HA), we demonstrate that exclusively films
constructed with poly(arginine) composed of 30 residues
(PAR30) acquire a strong antimicrobial activity against Gram-
positive and Gram-negative pathogenic bacteria associated
with infections of medical devices. This chain-size effect is extremely striking and is the first example reported where the length of
the polyelectrolytes played a key-role in the functionality of the films. Moreover, this unexpected functionality of nanolayered
polypeptide/polysaccharide PAR30/HA films occurs without adding any specific antimicrobial agent, such as antibiotics or
antimicrobial peptides. PAR30/HA film inhibits bacteria through a contact-killing mechanism due to the presence of mobile
PAR30 chains. These chains are assumed to diffuse toward the interface, where they interact with the bacteria with the consequence of killing them. This new coating with unique properties based on the association of a homopolypeptide of 30 residues with a polysaccharide constitutes a simple system to prevent implant-related infections with a reasonable production cost.

We investigate the viscosity dependence on
concentration and molecular weight of semiflexible polyelectrolyte
sodium carboxymethylcellulose (NaCMC) in aqueous salt-free and
NaCl solutions. Combining new measurements and extensive
literature data, we establish relevant power laws and crossovers
over a wide range of degree of polymerization (N) as well as
polymer (c) and salt (cs) concentrations. In salt-free solution, the
overlap concentration shows the expected c* ∝ N−2 dependence,
and the entanglement crossover scales as ce ∝ N−0.6±0.3, in strong
disagreement with scaling theory for which ce ∝ c* is expected, but
matching the behavior found for flexible polyelectrolytes. A second crossover, to a steep concentration dependence for specific viscosity (ηsp ∝ c3.5±0.2), commonly assigned to the concentrated regime, is shown to follow c** ∝ N−0.6±0.2 (with c**/ce ≃ 6) which thus suggests instead a dynamic crossover, possibly related to entanglement. The scaling of c* and ce in 0.01 and 0.1 M NaCl shows neutral polymer in good solvent behavior, characteristic of highly screened polyelectrolyte solutions. This unified scaling picture enables the estimation of viscosity of ubiquitous NaCMC solutions as a function of N, c, and cs and establishes the behavior expected for a range of semiflexible polyelectrolyte solutions.

Complexes of polyelectrolytes (PECs) are oppositely charged polymers assemblies held together by electrostatic interaction. As the non-covalent assembly of macromolecules/colloids in solution has been thoroughly investigated over the last decade with a particular emphasis put on the morphology of the final aggregates as a function of the building blocks-chemistry, the objective of this thesis is to come to a better understanding of the influence of interaction strength between polyelectrolytes on complexes morphologies, as well as kinetics and thermodynamics of the complexation. For this study, weakly and strongly interacting systems given rise to coacervate and precipitate phases has been elected. Those systems have been studied on a wide charge ratio scale (Z[+]/[-]) to span several physical states of the PECs (soluble and colloidal PECs, dense phases). Morphologies of assemblies are assessed by microscopy (optical, fluorescence, atomic force) and scattering techniques (neutron, light). Kinetics and thermodynamics of the complexation process are studied by use of a stopped-flow mixing device and an isothermal titration calorimeter. Results gave us keys to discriminate strongly interacting systems from weakly interacting ones. In particular, the ‘strong systems’ are showed to be non-equilibrium assemblies, ie. the formulation pathway or the way these different macromolecules are coming into contact is then a key step. Another important aspect that could explain the complexation process behavior is the hydration energy of the polyelectrolytes. Calorimetry measurements have been performed for numerous polyelectrolytes and then correlated to complexes properties.

There is no doubt that the chemical water treatment has resolved the problem of drinking water supply for several decades to humankind especially in terms of pathogen microorganisms and turbidity removal. However, due to chemicals used through this treatment and increasing quantities of pollutants discharged into nature, numerous health problems have been largely more and more proved and reported. This review discusses the toxicity of chlorine, alum, and polyelectrolyte which are widely employed through the world. The main addressed question here is: When the true and radical water treatment technology will be really and definitely applied? There is no water treatment technique but only distillation process which is successfully applied at the largest scale in nature by God. At least, physical processes such as membrane processes should be more and more applied through water treatment plants for reducing chemicals use. Most of chlorination disadvantages may be avoided through a better understanding of the mutual actions conducting to the generation of chlorine by-products and the use of more sophisticated procedures to assess toxicity capacity of such chemicals. Finally, this study arrives at its time since the Environmental Engineers and the Green Chemistry specialists have largely opened the discussion about polluting industry and preserving nature. Returning Man to its initial and noble Mission on Earth is reflected through this research to preserve both humankind and nature.

PEMBENTUKAN SPONTAN KOMPLEK POLIELEKTROLIT FIBROIN SUTERA DENGAN ALGINAT SEBAGAI MODEL PENGHANTARAN OBAT (Gita Cahya Eka Darma) Fibroin Sutera (SF) dan Alginat (ALG) merupakan biomaterial yang memiliki efek terapeutik dalam pengobatan luka yaitu hemostatik, dan kemampuannya dalam menyerap eksudat luka. Agen terapetik alami memiliki banyak keunggulan daripada penggunaan obat sintetik kimiawi, sehingga menjadikannya sebagai alternatif pilihan yang baik dalam pengobatan. Penelitian ini bertujuan membuat model penghantaran untuk pengobatan luka yaitu berupa membran serat hasil kompleksasi polielektrolit (PEC) melalui metode koaservasi. SF dari kepompong ulat sutera (Bombyx mori Linn) digunakan sebagai agen polikation, ALG sebagai agen polianion dan Kloramfenikol (CHL) sebagai model obatnya. Karakterisasi membran serat PEC yang dilakukan meliputi analisis gugus fungsi (FTIR), derajat kristalinitas (XRD), sifat termal (DSC), mikroskopik (SEM). Kemudian, dilakukan perhitungan perolehan koaservat (coacervation yield), uji keabuhan (swelling), dan uji pelepasan CHL secara in‒vitro. SDS PAGE digunakan untuk mengidentifikasi protein. Penelitian ini telah menghasilkan SF dengan karakteristik baru yang lebih baik, sehingga diperoleh membran serat PEC yang sesuai sebagai model penghantaran untuk pengobatan luka pada kulit. Membran serat PEC merupakan hasil modifikasi dari koaservat SF‒ALG berbentuk hidrogel. SF dalam membran berada pada konformasi strukturnya yang stabil yaitu Silk II dengan derajat kristalinitas dari SF maupun ikat‒silang elektrostatik SF‒ALG yang baik, sehingga membran serat ini dapat mengembang atau larut bergantung pada pH sistem. Analisis karakteristik membran telah membuktikan bahwa terjadi ikat‒silang elektrostatik antara SF dengan ALG, bentuk polimorf serta derajat kristalinitas SF dan membran dapat dikendalikan sehingga menentukan hasil akhir membran. Membran serat PEC responsif terhadap kondisi keasaman sistem, pada pH < 3 membran mengembang sementara pH > 3‒5,5 membran melarut sehingga dapat disesuaikan dengan kondisi pH tempat pelepasannya. Profil keabuhan meningkat dari pH 1 menuju pH 3 dengan persentase paling rendah adalah 414,3% (F3) dan paling tinggi adalah 844,4% (F2). Profil pelepasan CHL dari F1‒F3 berturut-turut adalah 91,33; 98,88; 81,94% selama 30 menit. Pelepasan paling cepat diperoleh dari formula dengan jumlah ALG lebih besar, sebaliknya pada jumlah SF lebih besar maka pelepasannya lebih lama sehingga rasio ini dapat menentukan jenis pelepasan yang diinginkan. Kata kunci: Fibroin sutera, natrium alginat, koaservasi, komplek polielektrolit, membran serat -------------------------------------------------------------------------------------------------------------------------------------------
SELF-ASSEMBLED POLYELECTROLYTE COMPLEX OF SILK FIBROIN WITH ALGINATE AS DRUG DELIVERY MODEL (Gita Cahya Eka Darma) Silk Fibroin (SF) and Alginate (ALG) are biomaterial that have therapeutic efect in wound dressing which is hemostatic, and the ability upon absorption of wound exudates. Natural therapeutic agents has many advantages than the use of chemical synthetic drugs, so that making it a good alternative in the medication. This research aims to make delivery model for wounds dressing in the form of fiber membrane results from polyelectrolyte complexation (PEC) through coacervation method. SF from silkworm cocoons (Bombyx mori Linn) used as polycations agent, ALG as polyanions agent and Chloramphenicol (CHL) as drug model. Characterization of PEC fiber membranes are conducted with analysis of the functional groups (FTIR), crystallinity degree (XRD), thermal properties (DSC), microscopic (SEM). Then, the study continued to the measurement of coacervation yield, swelling test, and in-vitro drug release test. SDS PAGE was used to verify the protein. This research has gained SF with better new characteristics, in order to obtain the appropriate PEC fiber membrane as delivery models for the treatment of skin wounds. PEC fiber membrane is a modified version from hydrogel-forming of SF‒ALG coacervate. SF in the membrane is in the stable conformation structure (Silk II) with a proper cystallinity degrees of SF and the SF‒ALG electrostatic crosslinking, so this fiber membrane can swelling or dissolve depending on the pH of the system. Characterization analysis of the membrane shown that the electrostatic bonds occurs between SF with ALG, polymorphic forms of the protein fibroin and crystallinity degree of SF and membrane can be controlled to determine the final result of the membrane. PEC fiber membrane is responsive to pH, at pH < 3 swelling occurs while at pH > 3‒5,5 it dissolved, this condition could be adjusted to the pH condition of the site released. The swelling profile increased from pH 1 upto pH 3 with the lowest percentage is 414,3% (F3) and the highest is 844,4% (F2). The CHL release profile of F1‒F3 respectively are 91,33; 98,88; 81,94% during 30 minute. The fastest drug release profile obtained from the formula with a higher amount of ALG, and otherwise on the formula that SF amounts is higher then the release is slower, this ratio can determine the type of release as required. Keywords: Silk fibroin, sodium alginate, coacervation, polyelectrolyte complex, fiber membrane

The rheology of water-soluble polyelectrolytes at intermediate and high concentrations is controlled by entanglement, hydrophobic, and electrostatic interactions, whose influences are difficult to isolate. We investigate the rheology of semidilute solutions of sodium carboxymethyl cellulose (NaCMC) with molecular weight M w ≃ 2.5 × 10 5 g/ mol and varying degree of substitution (DS) as a function of polymer concentration in various solvent media: salt-free water (long-ranged electrostatic interactions), 0.5 M aqueous NaCl (screened electrostatics), and 0.5 M aqueous NaOH (screened electrostatics, diminished hydrophobic interactions) in order to selectively examine the role played by these different interactions. Decreasing DS is found to decrease solubility and induce partial aggregation and eventual gelation. In salt-free and 0.5 M NaCl solution, NaCMC with DS ≃ 1.2 exhibits hydrophilic polyelectrolyte and neutral polymer in good solvent behavior, respectively. Decreasing DS to ≃0.7−0.8 leads to hydrophobic behavior in both media, becoming weak gels at high concentrations. In 0.5 M NaOH (pH = 13.5) the viscosities of solutions with different DS become identical when plotted against the overlap parameter, which we interpret as resulting from the solubilization of unsubstituted cellulose blocks. Small-angle neutron scattering (SANS) data indicate that the polymer conformation is not strongly affected by hydrophobic interactions. By varying DS, ionic strength, and pH, we demonstrate the tuning of NaCMC−solvent interactions, controlling separately the electrostatic and hydrophobic effects on the solution rheology.

Adsorption of polyelectrolytes to surfaces of opposite charge typically leads to charge neutralization and subsequent charge reversal. As can be shown by direct force measurements and stability studies, the interaction forces are dominated by repulsive forces originating from diffuse layer overlap and attractive van der Waals forces, in line with the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO).