Chitosan based bioadhesives for biomedical applications: A review.

Due to the promising properties of chitosan for biomedical engineering applications like biodegradability, biocompatibility, and non-toxicity, it is one of the most interesting biopolymers in this field. Therefore, Chitosan and its derivatives have attracted great attention in vast variety of biomedical applications. In the current paper, different types of chitosan-based bioadhesives including passive and active and their different types of external stimuli response structure such as thermo, pH and Light responsive systems are discussed.

Delivery of pharmaceuticals and other active ingredients with their crystalline cyclodextrin inclusion compounds.

In honor of Prof. Thorsteinn Loftsson's 70th birthday, we offer this personal review of our work using cyclodextrins (CDs) complexed with a variety of active ingredients, including pharmaceuticals, for the purpose of improving their delivery to polymer materials, e.g.

Physical Characterization of Inclusion Complexes of Triphenyl Phosphate and Cyclodextrins in Solution.

The goal of this work is to provide physical insights into the formation and stability of inclusion complexes (ICs) in aqueous solution between cyclodextrins (CDs) and a common flame retardant, triphenyl phosphate (TPP). Quantum chemistry calculations reveal the possible energetically favorable geometries of TPP in their 1:1 IC form with α-, β-, and γ-CDs as well as their associated complexation, conformational, and interaction energies. High-resolution mass spectrometry (MS) and tandem MS were used with electrospray ionization to study the soluble ICs formed between TPP and CDs.

Nanoscale Restructuring of Polymer Materials to Produce Single Polymer Composites and Miscible Blends.

I summarize work conducted in our laboratories over the past 30 years using small host molecules to restructure polymer materials at the nanometer level. Certain small molecules, such as the cyclic starches cyclodextrins (CDs) and urea (U) can form non-covalent crystalline inclusion compounds (ICs) with a range of guest molecules, including many polymers. In polymer-CD- and -U-ICs, guest polymer chains reside in narrow channels created by the host molecule crystals, where they are separated and highly extended.

Aliphatic Polyester Nanofibers Functionalized with Cyclodextrins and Cyclodextrin-Guest Inclusion Complexes.

The fabrication of nanofibers by electrospinning has gained popularity in the past two decades; however, only in this decade, have polymeric nanofibers been functionalized using cyclodextrins (CDs) or their inclusion complexes (ICs). By combining electrospinning of polymers with free CDs, nanofibers can be fabricated that are capable of capturing small molecules, such as wound odors or environmental toxins in water and air. Likewise, combining polymers with cyclodextrin-inclusion complexes (CD-ICs), has shown promise in enhancing or controlling the delivery of small molecule guests, by minor tweaking in the technique utilized in fabricating these nanofibers, for example, by forming core⁻shell or multilayered structures and conventional electrospinning, for controlled and rapid delivery, respectively.

Polymers Containing Non-Covalently Bound Cyclodextrins.

We summarize and review the formation, characterization, behaviors, and possible uses of polymers that are threaded through, but only partially covered by cyclodextrins (CDs), which we call non-stoichiometric polymer⁻CD inclusion compounds (ICs) or non-stoichiometric (n-s) polymer⁻CD ICs. Emphasis is placed on comparison of the behaviors of unthreaded neat polymers with those that are threaded through and partially covered by CDs. These comparisons lead to several suggested uses for (n-s) polymer⁻CD ICs.

Chitosan based hydrogels and their applications for drug delivery in wound dressings: A review.

Advanced development of chitosan hydrogels has led to new drug delivery systems that can release their active ingredients in response to environmental stimuli. This review considers more recent investigation of chitosan hydrogel preparations and the application of these preparations for drug delivery in wound dressings. Applications and structural characteristics of different types of active ingredients, such as growth factors, nanoparticles, nanostructures, and drug loaded chitosan hydrogels are summarized.

Nanoscale considerations responsible for diverse macroscopic phase behavior in monosubstituted isobutyl-POSS/poly(ethylene oxide) blends.

Nanocomposites prepared by incorporating functionalized polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford a wide range of versatile hybrid materials for use in technologies ranging from cosmetics and pharmaceuticals to sensors and batteries. Here, we investigate the phase behavior of nanocomposites composed of poly(ethylene oxide) (PEO) and monosubstituted isobutyl POSS (iPOSS) modified with different functional moieties. Microscopic analyses of blends containing these iPOSS variants reveal the existence of different macroscopic morphologies and surface topologies.

Estimation of the poly (ε-caprolactone) [PCL] and α-cyclodextrin [α-CD] stoichiometric ratios in their inclusion complexes [ICs], and evaluation of porosity and fiber alignment in PCL nanofibers containing these ICs.

This paper describes the utilization of Proton-Nuclear Magnetic Resonance spectroscopy ((1)H NMR) to quantify the stoichiometric ratios between poly (ε-caprolactone) [PCL] and α-cyclodextrin (α-CD) present in their non-stoichiometric inclusion complexes [(n-s)-ICs]. This paper further describes the porosity and fiber alignment of PCL nanofibers nucleated by the [(n-s)-ICs] during electrospinning. (1)H NMR indicated that the two non-stoichiometric inclusion complexes utilized in this study had differing stoichiometric ratios that were closely similar to those of the starting ratios used to make them.

Fabrication and Characterization of Poly(ε-caprolactone)/α-Cyclodextrin Pseudorotaxane Nanofibers.

Multifunctional scaffolds comprising neat poly(ε-caprolactone) (PCL) and α-cyclodextrin pseudorotaxanated in α-cyclodextrin form have been fabricated using a conventional electrospinning process. Thorough in-depth characterizations were performed on the pseudorotaxane nanofibers prepared from chloroform (CFM) and CFM/dimethylformamide (DMF) utilizing scanning electron microscopy (SEM), transmission electron microscopy (TEM), rheology, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), wide-angle X-ray diffraction (WAXD), and Instron tensile testing. The results indicate the nanofibers obtained from chloroform retain the rotaxanated structure; while those obtained from CFM/DMF had significantly dethreaded during electrospinning.

Poly(ε-caprolactone) nanowebs functionalized with α- and γ-cyclodextrins.

The effects of alpha- and gamma-cyclodextrins (α- and γ-CDs) on the thermal and crystal nucleation behavior of electrospun poly(ε-caprolactone) (PCL) nanofibers have been investigated. PCL/CD composite nanofibers were obtained for the first time by electrospinning the mixture from chloroform/N,N-dimethylformamide (60:40). Scanning electron microscopy analyses indicated that neat PCL nanofibers have an average diameter of 400 nm, which increases with the addition of CDs.

Restructuring polymers via nanoconfinement and subsequent release.

During the past several years my students and I have been utilizing certain small-molecule hosts to create nanostructured polymers. This is accomplished by first forming noncovalently bonded inclusion complexes (ICs) between these small-molecule hosts and guest polymers, followed by the careful removal of the host crystalline lattice to obtain a coalesced bulk polymer. We have repeatedly observed that such coalesced polymer samples behave distinctly from those produced from their solutions or melts.

Effect of guest hydrophobicity on water sorption behavior of oligomer/alpha-cyclodextrin inclusion complexes.

Cyclomaltohexaose (alpha-cyclodextrin, alpha-CD) can form inclusion complexes (ICs) with polymer molecules in the columnar crystal structure in which alpha-CD molecules stack to form a molecular tube. Complementary water vapor sorption and wide-angle X-ray diffractomery (WAXD) were performed on oligomer/alpha-CD ICs to determine their structures and stabilities. To discern the effect of guest molecule hydrophobicity on water adsorption isotherms, polyethylene glycol (PEG, MW = 600 g/mol) and hexatriacontane (HTC) guests were used.

Structural study of irregular amino acid sequences in the heavy chain of Bombyx mori silk fibroin.

Recently, genetic studies have revealed the entire amino acid sequence of Bombyx mori silk fibroin. It is known from X-ray diffraction studies that the beta-sheet crystalline structure (silk II) of fibroin is composed of hexaamino acid sequences of GAGAGS. However, in the heavy chain of B.

Structure and stability of columnar cyclomaltooctaose (gamma-cyclodextrin) hydrate.

Rapid recrystallization of cyclomaltooctaose (gamma-cyclodextrin, gamma-CD) from aqueous solution resulted in formation of a columnar structure with only water as the guest molecule. Upon vacuum drying at 90 degrees C for 15 h, gamma-CD, which was initially in the columnar structure, became amorphous. Complementary water vapor sorption and wide-angle X-ray diffractometry experiments were performed on columnar gamma-CD in its vacuum dried and as-precipitated states to elucidate its stability in humid environments and the crystal structure present at varying sorption levels.

Structural studies of Bombyx mori silk fibroin during regeneration from solutions and wet fiber spinning.

Regenerated silk fibroin materials show properties dependent on the methods used to process them. The molecular structures of B. mori silk fibroin both in solution and in solid states were studied and compared using X-ray diffraction, FTIR, and (13)C NMR spectroscopy.

Structure and stability of columnar cyclomaltohexaose (alpha-cyclodextrin) hydrate.

Rapid recrystallization of cyclomaltohexaose (alpha-cyclodextrin, alpha-CD) from aqueous solution resulted in formation of the columnar crystal structure of alpha-CD containing only water as the guest molecule. Complementary water vapor sorption and wide-angle X-ray diffractometry (WAXD) experiments were performed on the alpha-CD columnar structure to elucidate the crystal structure present at varying sorption levels. Equilibrium isothermal water vapor sorption experiments at 40 degrees C revealed that the alpha-CD columnar structure is unstable above a water activity of approximately 0.

Two-phase channel structures based on alpha-cyclodextrin-polyethylene glycol inclusion complexes.

Wide-angle X-ray scattering observations of alpha-cyclodextrin (CD)-poly(ethylene glycol) (PEG) inclusion complexes (ICs) have shown for the first time that two crystalline columnar modifications (forms I and II) are produced in the process of their formation. This was made possible by precise azimuthal X-ray diffraction scanning of oriented IC samples. Form I is characterized by CDs threaded onto PEG chains and arranged along channels in the order head-to-head/tail-to-tail, while form II is formed by unbound CDs also arranged into columns in a head-to-tail and also possibly a head-to-head/tail-to-tail manner, probably as a result of template crystallization on the form I IC crystals.

Melting and crystallization behaviors of biodegradable polymers enzymatically coalesced from their cyclodextrin inclusion complexes.

Inclusion complexed (IC) and coalesced biodegradable poly(epsilon-caprolactone) (PCL), poly(L-lactic acid) (PLLA), and their diblock copolymer (PCL-b-PLLA) were achieved by forming ICs between host alpha-cyclodextrin(alpha-CD) and guest PCL, PLLA, and PCL-b-PLLA, followed by removing the alpha-CD host with an amylase enzyme. FTIR spectra of the coalesced polymers reveal that the host alpha-CD can be completely removed, without polymer degradation, by treatment with an amylase enzyme. The melting and crystallization behavior of these CD-IC treated polymers, which are crystallizable, biodegradable, and bioabsorbable, are investigated by differential scanning calorimetry (DSC) and polarized optical microscopy.

Formation of and coalescence from the inclusion complex of a biodegradable block copolymer and alpha-cyclodextrin. 2: A novel way to regulate the biodegradation behavior of biodegradable block copolymers.

A biodegradable block copolymer (PCL-b-PLLA, M(n) = 1.72 x 10(4), M(w)/M(n) = 1.37) of poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA) with very low crystallinity was obtained by forming the inclusion complex between alpha-cyclodextrin molecules and PCL-b-PLLA followed by coalescence of the guest polymer chains.