Stereocomplexes, based on biodegradable polymers and bioactive macromolecules

Noda

Kimura

et al. 2017

Sci Rep

D-configured poly(D-lactic acid) (D-PLA) and poly(D-2-hydroxy-3-methylbutanoic acid) (D-P2H3MB) crystallized separately into their homo-crystallites when crystallized by precipitation or solvent evaporation, whereas incorporation of L-configured poly(L-2-hydroxybutanoic acid) (L-P2HB) in D-configured D-PLA and D-P2H3MB induced co-crystallization or ternary stereocomplex formation between D-configured D-PLA and D-P2H3MB and L-configured L-P2HB. However, incorporation of D-configured poly(D-2-hydroxybutanoic acid) (D-P2HB) in D-configured D-PLA and D-P2H3MB did not cause co-crystallization between D-configured D-PLA and D-P2H3MB and D-configured D-P2HB but separate crystallization of each polymer occurred. These findings strongly suggest that an optically active polymer (L-configured or D-configured polymer) like unsubstituted or substituted optically active poly(lactic acid)s can act as “a configurational or helical molecular glue” for two oppositely configured optically active polymers (two D-configured polymers or two L-configured polymers) to allow their co-crystallization. The increased degree of freedom in polymer combination is expected to assist to pave the way for designing polymeric composites having a wide variety of physical properties, biodegradation rate and behavior in the case of biodegradable polymers.

mentioning

confidence: 99%

Configurational Molecular Glue: One Optically Active Polymer Attracts Two Oppositely Configured Optically Active Polymers

Noda

Kimura

et al. 2017

Sci Rep

“…Slager and Domb et al reported hetereo‐stereocomplexation between PDLA and L ‐configured peptides such as the luteinizing hormone‐releasing hormone (LHRH),117 leuproide (an LHRH nonapeptides analogue),118–121 and vapreotide (a cyclic octapeptide somatostatin analogue) 117–119. Hetero‐stereocomplexation was observed by the use of DSC,117,120 SEM,117–120 SAXS,118,119 cryogenic transmission electron microscopy (Cryo‐TEM),118,119 and confocal microscopy 120. In addition to DSC results, the increase in scattering intensity in SAXS suggested the formation of hetero‐stereocomplex particles, which was further evidenced by SEM and Cryo‐TEM and confocal microscopic photographs.…”

Section: Hetero‐stereocomplexationmentioning

confidence: 99%

Poly(lactide) Stereocomplexes: Formation, Structure, Properties, Degradation, and Applications

Macromolecular Bioscience

2005

1,243

956

Summary: Poly(lactide)s [i.e. poly(lactic acid) (PLA)] and lactide copolymers are biodegradable, compostable, producible from renewable resources, and nontoxic to the human body and the environment. They have been used as biomedical materials for tissue regeneration, matrices for drug delivery systems, and alternatives for commercial polymeric materials to reduce the impact on the environment. Since stereocomplexation or stereocomplex formation between enantiomeric PLA, poly(L‐lactide) [i.e. poly(L‐lactic acid) (PLLA)] and poly(D‐lactide) [i.e. poly(D‐lactic acid) (PDLA)] was reported in 1987, numerous studies have been carried out with respect to the formation, structure, properties, degradation, and applications of the PLA stereocomplexes. Stereocomplexation enhances the mechanical properties, the thermal‐resistance, and the hydrolysis‐resistance of PLA‐based materials. These improvements arise from a peculiarly strong interaction between L‐lactyl unit sequences and D‐lactyl unit sequences, and stereocomplexation opens a new way for the preparation of biomaterials such as hydrogels and particles for drug delivery systems. It was revealed that the crucial parameters affecting stereocomplexation are the mixing ratio and the molecular weight of L‐lactyl and D‐lactyl unit sequences. On the other hand, PDLA was found to form a stereocomplex with L‐configured polypeptides in 2001. This kind of stereocomplexation is called “hetero‐stereocomplexation” and differentiated from “homo‐stereocomplexation” between L‐lactyl and D‐lactyl unit sequences. This paper reviews the methods for tracing PLA stereocomplexation, the methods for inducing PLA stereocompelxation, the parameters affecting PLA stereocomplexation, and the structure, properties, degradation, and applications of a variety of stereocomplexed PLA materials. magnified image

“…On the other hand, HTSC of PLA was reported for the first time for d ‐configured PDLA and l ‐configured polypeptides such as vapreotide, insulin, leuprolide [luteinizing hormone‐releasing hormone (LHRH) nonapeptide analogue], octreotide . As a result of HTSC formation, microparticular precipitates form in acetonitrile or acetonitrile/water, which become insoluble in the solvents that dissolve PDLA . The crystallization of PDLA was reported to be induced or assisted by the presence of LHRH .…”

Section: Introductionmentioning

confidence: 99%

“…The crystallization of PDLA was reported to be induced or assisted by the presence of LHRH . HTSC microparticles showed a continuous release of the interlocked peptides for a period of one to three months, making them suitable for drug delivery system …”

Section: Introductionmentioning

confidence: 99%

Heterostereocomplex‐ and Homocrystallization and Thermal Properties and Degradation of Substituted Poly(lactic acid)s, Poly(l‐2‐hydroxybutanoic acid) and Poly(d‐2‐hydroxy‐3‐methylbutanoic acid)

Macro Chemistry & Physics

Hayakawa

2016

Heterostereocomplex‐ and homocrystallization behavior, thermal properties and degradation of neat poly(l‐2‐hydroxybutanoic acid) [P(l‐2HB)], poly(d‐2‐hydroxy‐3‐methylbutanoic acid) [P(d‐2H3MB)], and their equimolar blend are first investigated. Regime I and II kinetics are observed for neat P(l‐2HB), whereas regime II and III kinetics are seen for the blend. The growth geometry of the neat P(l‐2HB) is linear and circular while that of the blend is spherical, whereas that of the neat P(d‐2H3MB) changes from linear to spherical, depending on crystallization temperature (T c). The main crystalline species is heterostereocomplex (HTSC) in the blend for a wide T c range of 0–180 °C and a very small amount of P(d‐2H3MB) homocrystallites form for melt‐crystallization at T c below 70 °C and solution‐crystallization. The equilibrium melting temperature of P(l‐2HB)/P(d‐2H3MB) HTSC crystallites (234.5 °C) is higher than those of P(l‐2HB) and P(d‐2H3MB) homocrystallites (114.9 and 208.6 °C, respectively). The activation energy values for thermal degradation of the P(l‐2HB)/P(d‐2H3MB) blend (190–219 kJ mol−1) are between those of neat P(l‐2HB) and P(d‐2H3MB) (164–180 and 210–380 kJ mol−1, respectively), reflecting that the interaction between the polymers with opposite configurations is similar to or lower than that between the polymers with the same configurations at a high temperature in the melt.