JP2004035791A - Temperature responsive polymer and temperature responsive gel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new temperature responsive polymer and temperature responsive gel having biodegradability and enabling easy functionalization. <P>SOLUTION: The temperature responsive polymer is composed of a repeating unit (A) of formula (1) and a repeating unit (B) of formula (2) each composed of an α/β-asparagine derivative unit having a substituent on nitrogen atom. In the formulas, R<SP>1</SP>is a hydroxyalkyl such as hydroxypentyl; and R<SP>2</SP>is a hydroxyalkyl different from R<SP>1</SP>such as hydroxyhexyl, an alkyl or an aryl. The polymer can be produced by mixing a polysuccinimide, R<SP>1</SP>NH<SB>2</SB>and R<SP>2</SP>NH<SB>2</SB>in an organic solvent (the ratio of the amines is 5:95 to 95:5) and, in the case of gelatinizing, crosslinking the mixed product with a polyfunctional compound such as an α ,ω-alkylene diisocyanate. <P>COPYRIGHT: (C)2004,JPO

Description

【化６】

（式中、Ｒ^１はヒドロキシアルキル基、Ｒ^２はＲ^１と異なるヒドロキシアルキル基、アルキル基またはアリール基を表す。）
【０００８】
この発明の温度応答性ポリマーは、繰り返し単位（Ａ）、（Ｂ）がともに窒素上に置換基を有するα／β−アスパラギン誘導体ユニットである。その化学構造からして、生医学用材料として既に幅広く用いられている従来のポリアミノ酸と同様に、生体適合性、生分解性に優れていることは明らかである。念のため詳述すると、ポリアクリル酸の代用を目指した生分解性ポリマーとして良く知られたポリ（α／β−アスパラギン酸ナトリウム）は、アスパラギン酸を熱重合し、得られたポリコハク酸イミドをアルカリ加水分解して得られる。この発明の温度応答性ポリマーは、そのアルカリの代わりにアミンを反応させることにより得られるものだからである。
【０００９】
ここでもう一つ重要な事は、Ｒ^２がＲ^１と異なるという限定事項である。即ち、Ｒ^１がヒドロキシアルキル基であって、Ｒ^２はアルキル基もしくはアリール基であるかまたはＲ^１と異なるヒドロキシアルキル基であることを要する。これにより温度応答性を示すからである。ちなみにＲ^２がＲ^１と同一であるポリマーが既に合成されているが（例えばＧ．　Ｃａｌｄｗｅｌｌ　ｅｔ　ａｌ．，　Ｊ．　Ａｐｐｌ．　Ｐｏｌｙｍ．　Ｓｃｉ．，　６６，　９１１　（１９９７））、これは温度応答性を示さない。
【００１０】
更にもう一つ重要なことは、少なくともＲ^１がヒドロキシアルキル基である点である。これにより、繰り返し単位（Ａ）毎に様々な官能基や機能性団をそこに導入し、ポリマーを機能化することができるからである。
Ｒ^１及びＲ^２の組み合わせとして好ましいのは、Ｒ^１が４‐ヒドロキシブチル基、５‐ヒドロキシペンチル基及び６‐ヒドロキシヘキシル基のうちから選ばれる１種、Ｒ^２が３‐ヒドロキシプロピル基、４‐ヒドロキシブチル基、５‐ヒドロキシペンチル基、６‐ヒドロキシヘキシル基、メチル基、エチル基、ｎ−プロピル基及びｉ−プロピル基のうちから選ばれる１種である。この組み合わせである場合、特に鋭敏な温度応答性を示すからである。
【００１１】
また、前記繰り返し単位（Ａ）と（Ｂ）の好ましいモル組成比は、９５：５〜５：９５である。尚、Ｒ^１及びＲ^２がともにヒドロキシアルキル基である場合、炭素数の少ないヒドロキシアルキル基を有する繰り返し単位の割合が増すほど相転移温度が高くなる。特にＲ^１が５−ヒドロキシペンチル基、Ｒ^２が６−ヒドロキシヘキシル基であって、繰り返し単位（Ａ）と（Ｂ）のモル組成比が５０：５０〜３０：７０の範囲であるとき、２５℃〜４０℃で温度応答性を示す。
【００１２】
この発明の温度応答性ポリマーの好ましい数平均分子量は１，０００〜１，０００，０００の範囲である。１，０００に満たないと材料強度が不十分であり、１，０００，０００を超えると完全に生分解するまでに著しい長時間を要するからである。
【００１３】
次にこの発明の温度応答性ポリマーを製造する適切な方法は、Ｒ^１がヒドロキシアルキル基、Ｒ^２がＲ^１と異なるヒドロキシアルキル基、アルキル基またはアリール基を表すとするとき、ポリコハク酸イミド、Ｒ^１ＮＨ_２及びＲ^２ＮＨ_２を有機溶媒中で混合することを特徴とする。原料となるポリコハク酸イミドは、アスパラギン酸を熱重合することによって得られるが、市販されていれば、それを用いても良い。この方法によれば、Ｒ^１ＮＨ_２及びＲ^２ＮＨ_２の混合比によって、得られる温度応答性ポリマー中の繰り返し単位（Ａ）と（Ｂ）の比率を制御することができる。
【００１４】
上記のランダム共重合体を多官能性化合物で架橋するとゲル化し、温度応答性ゲルとなる。そして、この多官能性化合物がα、ω−アルキレンジイソシアネートなどのジイソシアネート類であると、下記一般式で示される架橋構成単位を有する、生分解性を維持した温度応答性ゲルとなる。
【００１５】
【化７】

【００１６】
（式中、Ｘ及びＺは前記Ｒ^１またはＲ^２から水酸基を除いた残基、Ｙはアルキレン基を表す。）
上記のようにこの発明の温度応答性ゲルは、Ｒ^１及びＲ^２の組み合わせと、繰り返し単位（Ａ）と（Ｂ）の比率とによって人体に対して適温で鋭敏な温度応答性を示すことから、これを薬物徐放材料として用いることができる。
【００１７】
【発明の実施の形態】
本発明の繰り返し単位（Ａ）と（Ｂ）は温度応答性を示すものならば、任意に組み合わせることができる。繰り返し単位（Ａ）において、Ｒ^１の具体例として２‐ヒドロキシエチル基、３‐ヒドロキシプロピル基、２‐ヒドロキシプロピル基、４‐ヒドロキシブチル基、２‐ヒドロキシブチル基、２‐（ヒドロキシメチル）プロピル基、２‐ヒドロキシペンチル基、３‐ヒドロキシ‐２，２‐ジメチルプロピル基、３‐ヒドロキシペンチル基、５‐ヒドロキシペンチル基、６‐ヒドロキシヘキシル基、２‐ヒドロキシヘキシル基、７‐ヒドロキシヘプチル基、８‐ヒドロキシオクチル基等のヒドロキシアルキル基が挙げられる。鋭敏な温度応答性を発現させるためには、前記の通り適度な親水性を有する４‐ヒドロキシブチル基、５‐ヒドロキシペンチル基、６‐ヒドロキシヘキシル基等が望ましい。
【００１８】
繰り返し単位（Ｂ）におけるＲ^２は、繰り返し単位（Ａ）のＲ^１と異なる構造である。Ｒ^２の具体例として、２‐ヒドロキシエチル基、３‐ヒドロキシプロピル基、２‐ヒドロキシプロピル基、４‐ヒドロキシブチル基、２‐ヒドロキシブチル基、２‐（ヒドロキシメチル）プロピル基、２‐ヒドロキシペンチル基、３‐ヒドロキシ‐２，２‐ジメチルプロピル基、３‐ヒドロキシペンチル基、５‐ヒドロキシペンチル基、６‐ヒドロキシヘキシル基、２‐ヒドロキシヘキシル基、７‐ヒドロキシヘプチル基、８‐ヒドロキシオクチル基等のヒドロキシアルキル基、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、ｉｓｏ−ブチル基、２−ブチル基、ｔ−ブチル基、ｎ−ペンチル基、ｎ−ヘキシル基、ｎ−ヘプチル基、ｎ−オクチル基、ｎ−デシル基、ｎ−ドデシル基、ｎ−オクタデシル基などのアルキル基、フェニル基、２−メチルフェニル基、３−メチルフェニル基、４−メチルフェニル基、４−エチルフェニル基、１−ナフチル基、２−ナフチル基などのアリール基が挙げられる。鋭敏な温度応答性を発現させるためには、前記の通り適度な親水性を有する３‐ヒドロキシプロピル基、４‐ヒドロキシブチル基、５‐ヒドロキシペンチル基、６‐ヒドロキシヘキシル基、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基等が望ましい。
【００１９】
上記の温度応答性ポリマーを、ポリコハク酸イミドと二種類のアミンとを有機溶媒中で反応させることにより合成する場合、アミンの量はモル当量でポリコハク酸イミドより多ければ特に限定されないが、１．１〜１０倍が好ましい。用いる有機溶媒は両基質を溶解する溶媒であれば特に限定されないが、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチルピロリドン、ジメチルスルホキシドなどが挙げられる。反応温度、反応時間は用いるアミン種により異なるが、０〜１５０℃、１分〜１２０時間、好ましくは３０〜８０℃、３０分〜４８時間の範囲である。
【００２０】
繰り返し単位（Ａ）及び（Ｂ）を構成成分とするランダム共重合体から温度応答性ゲルを作製する方法としては種々の方法があるが、一般には前記の通りランダム共重合体の側鎖アルコールと架橋剤との反応により達成可能である。架橋剤としてはアルコールと反応する多官能性化合物であれば、特に限定されない。一般に生分解性温度応答性ゲルの作製においてはジイソシアネートが用いられ、その具体例としては、１，２−エタンジイソシアネート、１，３−プロパンジイソシアネート、１，４−ブタンジイソシアネート、１，５−ペンタンジイソシアネート、１，６−ヘキサンジイソシアネート、１，８−オクタンジイソシアネート、１，１０−デカンジイソシアネート、１，１２−ドデカンジイソシアネート、１，３−トルイジンジイソシアネート、１，２−フェニレンジイソシアネート、１，３−フェニレンジイソシアネート、１，４−フェニレンジイソシアネート、コハク酸クロリド、グルタル酸クロリド、アジピン酸クロリド、セバシン酸クロリド、フタル酸クロリド、テレフタル酸クロリド等が挙げられる。このゲルに鋭敏な温度応答性を発現させる架橋剤としてはジイソシアネートが好ましく、特に適度な親水性を有する１，４−ブタンジイソシアネート、１，５−ペンタンジイソシアネート、１，６−ヘキサンジイソシアネート、１，８−オクタンジイソシアネート等が望ましい。
【００２１】
架橋剤の使用量は繰り返し単位（Ａ）及び（Ｂ）の合計量に対して０．１〜５０モル％、好ましくは２〜３０モル％である。用いる有機溶媒は上記ランダム共重合体が溶解し、イソシアネート基と反応しないものであれば、特に限定されないが、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチルピロリドン、ジメチルスルホキシドなどが挙げられる。反応温度、反応時間は用いるジイソシアネート種により異なるが、０〜１５０℃、１時間〜１２０時間、好ましくは３０〜８０℃、３時間〜４８時間の範囲である。
【００２２】
【実施例】
ここで、本発明の一実施例を説明するが、本発明は、下記の実施例に限定して解釈されるものではない。また、本発明の要旨を逸脱することなく、適宜変更することが可能であることは言うまでもない。
【００２３】
−実施例１−
５０ミリリットルナスフラスコに、ポリコハク酸イミド（０．４９グラム、５．０ｍｍｏｌモノマーユニット）、５−アミノペンタノール（０．５２グラム、５．０ｍｍｏｌ）、６−アミノヘキサノール（０．５９グラム、５．０ｍｍｏｌ）を取り、７．５ミリリットルのＮ，Ｎ−ジメチルホルムアミドを加えて室温で攪拌し、溶解させた。その後、５０℃で２４時間反応させた。反応溶液を排除分子量千の透析膜を用いて、水からの透析によりポリマーを単離した。収量０．９２グラム（収率８９％）。ポリマーの構造は４００ＭＨｚ　^１Ｈ　ＮＭＲにより確認し、仕込み比通りのポリマーとなっていることを確認した。
【００２４】
^１Ｈ　ＮＭＲ（ＤＭＳＯ−ｄ_６，　ｐｐｍ）　１．２−１．６　（ｂｒ，　ＣＨ_２ＣＨ_２ＣＨ_２），　２．９−３．１　（ｂｒ，　ＮＨＣＨ_２ＣＨ_２），　３．３−３．６　（ｂｒ，　Ｃ（＝Ｏ）ＣＨ_２ＣＨＣ（＝Ｏ）），　４．２−４．８　（ｂｒ，　Ｃ（＝Ｏ）ＣＨ_２ＣＨＣ（＝Ｏ），　ＣＨ_２ＯＨ），　７．５−８．５　（ｂｒ，　ＮＨ）．
分子量は溶離剤として０．１Ｍ　ＬｉＣｌ／ＤＭＦを使用してＧＰＣによって決定した。その結果、数平均分子量が２２０００、分子量分布が３．１であった。
【００２５】
［相転移温度の測定その１］
上記ポリマーの１重量％濃度の溶液を調製し、その溶液を１℃／分で昇温（あるいは降温）し、温度調整機能付きのＵＶ−可視分光光度計を用いて昇温（あるいは降温）中における波長５００ｎｍでの透過率を測定した。横軸に溶液の温度、縦軸に透過率をとって測定結果を表したグラフを図１に示す。図１に見られるように、この実施例のポリマーは昇温時、降温時いずれでも鋭敏な温度応答性を示した。昇温時の透過率９０％を示す温度を相転移温度と定めると、２３℃であった。
【００２６】
［相転移温度の測定その２］
上記ポリマーの０．１重量％水溶液を用いて、動的光散乱装置（大塚電子製ＤＬＳ７０００）で粒子径を測定した。結果を図２に示す。２５℃以下では粒子径は１０ｎｍ以下であったが、３０℃以上で粒子径が約２５０ｎｍとなり、ポリマーが凝集していることが明らかとなった。従って、この方法でも相転移温度が２５℃付近であることが認められた。
【００２７】
−実施例２〜４−
実施例２〜４では、５−アミノペンタノールと６−アミノヘキサノールの使用量を変えた以外は実施例１と同一条件でポリマーを製造した。各条件毎のポリマーの収率、数平均分子量、分子量分布及び相転移温度の結果を実施例１の結果を併せて表１に示す。
【００２８】
【表１】

【００２９】
いずれも場合も得られたポリマーは、仕込み比の通りの組成比を有していた。また、実施例２〜４で得られたポリマーの昇温時の相転移挙動を図３に示す。いずれのポリマーも鋭敏な温度応答性を示し、しかも５−アミノペンタノールの導入量が高い試料ほど相転移温度が上昇した。
【００３０】
−比較例１−
５−アミノペンタノール（０．５２グラム、５．０ｍｍｏｌ）及び６−アミノヘキサノール（０．５９グラム、５．０ｍｍｏｌ）に代えて５−アミノペンタノール（１．０４グラム、１０．０ｍｍｏｌ）とした以外は実施例１と同一条件でポリマーを製造した。得られたポリマーの水溶液は、０〜１００℃で相転移を示さなかった。
【００３１】
−比較例２−
５−アミノペンタノール（０．５２グラム、５．０ｍｍｏｌ）及び６−アミノヘキサノール（０．５９グラム、５．０ｍｍｏｌ）に代えて６−アミノヘキサノール（１．１８グラム、１０．０ｍｍｏｌ）とした以外は実施例１と同一条件でポリマーを製造した。得られたポリマーは、０〜１００℃で水に溶解しなかった。
【００３２】
−実施例５−
［ゲルの作製］
５−アミノペンタノール（０．５２グラム、５．０ｍｍｏｌ）及び６−アミノヘキサノール（０．５９グラム、５．０ｍｍｏｌ）に代えて、４−アミノブタノール（５．０ｍｍｏｌ）及び５−アミノペンタノール（５．０ｍｍｏｌ）とした以外は実施例１と同一条件でポリマーを製造した。このポリマー０．６グラムと、１，６−ヘキサンジイソシアネート４５μＬ（１０モル％）をＮ，Ｎ−ジメチルホルムアミド３ｍＬに溶解させた。この溶液を３ｍｍの間隔を有する二枚の板（材質：テトラフルオロエチレン重合体）の間に封入し液膜とした。このまま６０℃、２４時間反応させて、その後純水で洗浄し、定量的にゲルを得た。
【００３３】
［膨潤度の測定］
このゲルを５℃〜７０℃の所定温度の水中で５時間保持し、膨潤させた。この膨潤ゲルを取り出して重量を測定し、乾燥時の重量との比を膨潤度と定めた。膨潤度の温度応答性を図４に示す。このゲルは２０℃までは８倍程度膨順したが、温度をあげるにつれて膨潤度が低下し、４０℃以上ではほとんど膨潤せず、膨潤度が一定となった。これより、本ゲルは温度応答性を示すことが明らかとなった。
【００３４】
［徐放性評価］
ブリリアントブルーＦＦの０．２％水溶液に実施例５のゲルを一週間漬け、その後表面に付いたブリリアントブルーＦＦを水でよく洗い流した。このブリリアントブルーＦＦ含有ゲルを所定温度の水につけ、漏れ出たブリリアントブルーＦＦ量をＵＶ−可視分光光度計を用い、波長６３０ｎｍの吸光度変化から求めた。結果を図５に示す。５０℃でのブリリアントブルーＦＦの放出は３０℃より早いことがわかった。これは図４に示されるように、５０℃ではゲルが収縮するためにブリリアントブルーＦＦの放出が早まったことによる。この結果より、本ゲルが温度により徐放性を制御できることが明らかとなった。
【００３５】
【発明の効果】
本発明の温度応答性ポリマー及び温度応答性ゲルは、ポリアミノ酸を基盤とするので生分解性を示す。また温度応答性ポリマーは側鎖に修飾可能な水酸基を有するので、種々の機能化も可能である。従って、本発明の温度応答性ポリマー及び温度応答性ゲルは、薬物徐放材料、メカノケミカル材料、温度センサー、分離膜、保水剤等の用途として極めて有用である。
【図面の簡単な説明】
【図１】実施例１のポリマー溶液の透過率と温度との関係を示すグラフである。
【図２】実施例１のポリマー溶液中のポリマーの粒径と温度との関係を示すグラフである。
【図３】実施例１〜４の各ポリマー溶液の透過率と温度との関係を示すグラフである。
【図４】実施例５のゲルの膨潤度と温度との関係を示すグラフである。
【図５】実施例５のゲルによる薬剤の徐放性を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a temperature-responsive polymer and a temperature-responsive gel based on polyamino acids, and a method for producing the same. More specifically, the present invention relates to a temperature-responsive polymer material used for a sustained-release drug material, a mechanochemical material, a temperature sensor, a separation membrane, a water retention agent, and the like.
[0002]
[Prior art]
In recent years, stimulus-responsive materials have been actively developed. It is known that certain polymer compounds are in a homogeneously dissolved state below a certain temperature in a solution state, but cause phase separation into two phases having different compositions above a certain temperature. Such a polymer compound showing a phase transition at a constant temperature is generally called a temperature-responsive polymer. Further, a gel obtained by crosslinking such a polymer compound swells at a temperature lower than the phase transition temperature, releases a medium at a temperature higher than the phase transition temperature, and rapidly contracts in volume. Therefore, temperature-responsive gel is expected to be applied as a material for temperature-responsive drug sustained release.
[0003]
Typical examples of the temperature-responsive polymer include vinyl monomer-type polymers such as poly (N-isopropylacrylamide) and poly (methyl vinyl ether). In particular, the former has a phase transition temperature of about 32 ° C. which is close to room temperature, and is therefore being studied for use in the biomedical field. In recent years, a block polymer type biodegradable temperature-responsive polymer composed of polylactic acid and polyethylene glycol has also been developed (for example, B. Jong et al., Nature, 388, 860 (1997)).
[0004]
[Problems to be solved by the invention]
However, since the vinyl monomer type polymer does not undergo biodegradation, it has a disadvantage that the range of application in the biomedical field is limited. Moreover, in the case of poly (N-isopropylacrylamide), the application range is limited because N-alkylacrylamide, which is a monomer, emits a strong odor and has neurotoxicity. Further, although temperature control by a copolymerization method using N-isopropylacrylamide as a main monomer has been attempted, a wide range of temperature control is difficult, and there are many cases where a sharp temperature response is not exhibited.
[0005]
Furthermore, when a functional group or a functional group is introduced, the conventional vinyl monomer-type temperature responsive polymer does not show phase transition. Specifically, for example, even if an attempt is made to synthesize a temperature-responsive polymer having a carboxylic acid in the side chain by copolymerizing acrylic acid with N-isopropylacrylamide, the temperature-responsive property is increased only by copolymerizing a small amount of acrylic acid. It is not sensitive, and when it exceeds 10 mol%, it does not show temperature response. Therefore, it is difficult to functionalize a vinyl monomer type temperature-responsive polymer, and the development of its application to drug sustained release materials, mechanochemical materials, temperature sensors, and the like has been limited.
[0006]
Next, the above-mentioned block polymer type temperature-responsive polymer has a functional group only at the terminal and is difficult to function, and among its constituent units, polylactic acid is biodegradable, but polyethylene glycol is non-degradable. Because it is biodegradable, it is not completely biodegradable.
Therefore, an object of the present invention is to provide a new temperature-responsive polymer which has biodegradability and can be easily functionalized.
[0007]
[Means for Solving the Problems]
In order to solve the problem, the temperature-responsive polymer of the present invention is:
It is characterized by comprising a random copolymer having a repeating unit (A) represented by the following general formula (1) and a repeating unit (B) represented by the following general formula (2) as constituent components.
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(In the formula, R ¹ represents a hydroxyalkyl group, and R ² represents a hydroxyalkyl group, an alkyl group, or an aryl group different from R ^1. )
[0008]
The temperature-responsive polymer of the present invention is an α / β-asparagine derivative unit in which both the repeating units (A) and (B) have a substituent on nitrogen. From its chemical structure, it is clear that it has excellent biocompatibility and biodegradability, similarly to the conventional polyamino acids already widely used as biomedical materials. To make sure, in detail, poly (α / β-sodium aspartate), which is well-known as a biodegradable polymer aimed at substituting polyacrylic acid, thermally polymerizes aspartic acid and converts the resulting polysuccinimide. Obtained by alkaline hydrolysis. This is because the temperature-responsive polymer of the present invention is obtained by reacting an amine instead of the alkali.
[0009]
Another important point here is the limitation that R ² is different from R ¹ . That is, it is necessary that R ¹ is a hydroxyalkyl group and R ² is an alkyl group or an aryl group, or a hydroxyalkyl group different from R ¹ . This is because temperature responsiveness is exhibited. Incidentally, a polymer in which R ² is the same as R ¹ has already been synthesized (for example, G. Caldwell et al., J. Appl. Polym. Sci., 66, 911 (1997)). Not shown.
[0010]
Yet another important point is that at least R ¹ is a hydroxyalkyl group. This is because various functional groups and functional groups can be introduced into each repeating unit (A) to functionalize the polymer.
Preferred as a combination of R ¹ and R ² is that R ¹ is ^{one selected} from a 4-hydroxybutyl group, a 5-hydroxypentyl group and a 6-hydroxyhexyl group, R ² is a 3-hydroxypropyl group, -Hydroxybutyl group, 5-hydroxypentyl group, 6-hydroxyhexyl group, methyl group, ethyl group, n-propyl group and i-propyl group. This is because this combination exhibits particularly sharp temperature response.
[0011]
The preferred molar composition ratio of the repeating units (A) and (B) is from 95: 5 to 5:95. When both R ¹ and R ² are hydroxyalkyl groups, the phase transition temperature increases as the proportion of the repeating unit having a hydroxyalkyl group having a small number of carbon atoms increases. In particular, when R ¹ is a 5-hydroxypentyl group, R ² is a 6-hydroxyhexyl group, and the molar composition ratio of the repeating units (A) and (B) is in the range of 50:50 to 30:70, 25 It shows temperature responsiveness at -40 ° C.
[0012]
The preferred number average molecular weight of the temperature responsive polymer of the present invention is in the range of 1,000 to 1,000,000. If it is less than 1,000, the strength of the material is insufficient, and if it exceeds 1,000,000, it takes an extremely long time to completely biodegrade.
[0013]
Next, a suitable method for preparing the temperature responsive polymer of the present invention is to provide a polysuccinimide, wherein R ¹ represents a hydroxyalkyl group and R ² represents a hydroxyalkyl group, an alkyl group or an aryl group different from R ¹ . It is characterized in that R ¹ NH ₂ and R ² NH ₂ are mixed in an organic solvent. Polysuccinimide as a raw material is obtained by thermally polymerizing aspartic acid, but it may be used as long as it is commercially available. According to this method, the ratio of the repeating units (A) and (B) in the obtained temperature-responsive polymer can be controlled by the mixing ratio of R ¹ NH ₂ and R ² NH ₂ .
[0014]
When the above random copolymer is crosslinked with a polyfunctional compound, it gels and becomes a temperature-responsive gel. When the polyfunctional compound is a diisocyanate such as α, ω-alkylene diisocyanate, a temperature-responsive gel having crosslinked structural units represented by the following general formula and maintaining biodegradability is obtained.
[0015]
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[0016]
(In the formula, X and Z represent a residue obtained by removing a hydroxyl group from R ¹ or R ² , and Y represents an alkylene group.)
As described above, the temperature-responsive gel of the present invention exhibits a suitable and sharp temperature response to the human body by the combination of R ¹ and R ² and the ratio of the repeating units (A) and (B). This can be used as a drug sustained release material.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The repeating units (A) and (B) of the present invention can be arbitrarily combined as long as they exhibit temperature responsiveness. In the repeating unit (A), specific examples of R ¹ include 2-hydroxyethyl, 3-hydroxypropyl, 2-hydroxypropyl, 4-hydroxybutyl, 2-hydroxybutyl, and 2- (hydroxymethyl) propyl Group, 2-hydroxypentyl group, 3-hydroxy-2,2-dimethylpropyl group, 3-hydroxypentyl group, 5-hydroxypentyl group, 6-hydroxyhexyl group, 2-hydroxyhexyl group, 7-hydroxyheptyl group, And hydroxyalkyl groups such as 8-hydroxyoctyl group. In order to express a sharp temperature response, a 4-hydroxybutyl group, a 5-hydroxypentyl group, a 6-hydroxyhexyl group, etc. having an appropriate hydrophilicity as described above are desirable.
[0018]
R ² in the repeating unit (B) has a different structure from R ^{1 in the} repeating unit (A). Specific examples of R ² include 2-hydroxyethyl, 3-hydroxypropyl, 2-hydroxypropyl, 4-hydroxybutyl, 2-hydroxybutyl, 2- (hydroxymethyl) propyl, and 2-hydroxypentyl Group, 3-hydroxy-2,2-dimethylpropyl group, 3-hydroxypentyl group, 5-hydroxypentyl group, 6-hydroxyhexyl group, 2-hydroxyhexyl group, 7-hydroxyheptyl group, 8-hydroxyoctyl group, etc. Hydroxyalkyl group, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, iso-butyl group, 2-butyl group, t-butyl group, n-pentyl group, n-hexyl group , N-heptyl, n-octyl, n-decyl, n-dodecyl, n-octadecyl, etc. And aryl groups such as a phenyl group, a phenyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-ethylphenyl group, a 1-naphthyl group, and a 2-naphthyl group. In order to develop a sharp temperature response, a 3-hydroxypropyl group, a 4-hydroxybutyl group, a 5-hydroxypentyl group, a 6-hydroxyhexyl group, a methyl group, and an ethyl group having appropriate hydrophilicity as described above are required. , N-propyl and i-propyl.
[0019]
When the above-mentioned temperature-responsive polymer is synthesized by reacting polysuccinimide and two kinds of amines in an organic solvent, the amount of amine is not particularly limited as long as it is a molar equivalent larger than that of polysuccinimide. 1 to 10 times is preferred. The organic solvent to be used is not particularly limited as long as it dissolves both substrates, and examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide. The reaction temperature and reaction time vary depending on the type of amine used, but are in the range of 0 to 150 ° C, 1 minute to 120 hours, preferably 30 to 80 ° C, 30 minutes to 48 hours.
[0020]
There are various methods for producing a temperature-responsive gel from a random copolymer containing the repeating units (A) and (B) as constituents. This can be achieved by reaction with a crosslinking agent. The crosslinking agent is not particularly limited as long as it is a polyfunctional compound that reacts with alcohol. Generally, diisocyanate is used in the preparation of a biodegradable temperature-responsive gel, and specific examples thereof include 1,2-ethane diisocyanate, 1,3-propane diisocyanate, 1,4-butane diisocyanate, and 1,5-pentane diisocyanate. 1,6-hexane diisocyanate, 1,8-octane diisocyanate, 1,10-decane diisocyanate, 1,12-dodecane diisocyanate, 1,3-toluidine diisocyanate, 1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, Examples include 1,4-phenylene diisocyanate, succinic chloride, glutaric chloride, adipic chloride, sebacic chloride, phthalic chloride, and terephthalic chloride. A diisocyanate is preferable as a crosslinking agent that exhibits a sharp temperature response to the gel, and particularly, 1,4-butane diisocyanate, 1,5-pentane diisocyanate, 1,6-hexane diisocyanate, and 1,8 having moderate hydrophilicity. -Octane diisocyanate and the like are desirable.
[0021]
The amount of the crosslinking agent used is 0.1 to 50 mol%, preferably 2 to 30 mol%, based on the total amount of the repeating units (A) and (B). The organic solvent used is not particularly limited as long as the random copolymer dissolves and does not react with the isocyanate group. Examples of the organic solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide. Is mentioned. The reaction temperature and reaction time vary depending on the type of diisocyanate used, but are in the range of 0 to 150 ° C, 1 hour to 120 hours, preferably 30 to 80 ° C, 3 hours to 48 hours.
[0022]
【Example】
Here, one embodiment of the present invention will be described, but the present invention is not construed as being limited to the following embodiment. It goes without saying that changes can be made as appropriate without departing from the spirit of the present invention.
[0023]
-Example 1-
In a 50 ml eggplant flask, polysuccinimide (0.49 g, 5.0 mmol monomer units), 5-aminopentanol (0.52 g, 5.0 mmol), 6-aminohexanol (0.59 g, 5.0 mmol). 0 mmol), 7.5 ml of N, N-dimethylformamide was added, and the mixture was stirred and dissolved at room temperature. Thereafter, the reaction was carried out at 50 ° C. for 24 hours. The polymer was isolated by dialysis from water using a dialysis membrane with a molecular weight of 1,000. Yield 0.92 grams (89% yield). The structure of the polymer was confirmed by 400 MHz ¹ H NMR, and it was confirmed that the polymer had the same charge ratio as the charge.
[0024]
_{^{1 H NMR (DMSO-d 6}} , ppm) 1.2-1.6 (br, CH 2 CH 2 CH 2), 2.9-3.1 (br, NHCH 2 CH 2), 3.3-3 _{.6 (br, C (= O} ) CH 2 CHC (= O)), 4.2-4.8 (br, C (= O) CH 2 CHC (= O), CH 2 OH), 7.5 -8.5 (br, NH).
Molecular weight was determined by GPC using 0.1 M LiCl / DMF as eluent. As a result, the number average molecular weight was 22,000 and the molecular weight distribution was 3.1.
[0025]
[Measurement of phase transition temperature 1]
A 1% by weight solution of the above polymer is prepared, and the solution is heated (or cooled) at a rate of 1 ° C./min, and heated (or cooled) using a UV-visible spectrophotometer equipped with a temperature control function. Was measured at a wavelength of 500 nm. FIG. 1 is a graph showing the measurement results, with the horizontal axis representing the solution temperature and the vertical axis representing the transmittance. As shown in FIG. 1, the polymer of this example showed a sharp temperature response both when the temperature was raised and when the temperature was lowered. The temperature at which the transmittance of 90% at the time of raising the temperature was determined as the phase transition temperature was 23 ° C.
[0026]
[Measurement of phase transition temperature 2]
Using a 0.1% by weight aqueous solution of the above polymer, the particle size was measured with a dynamic light scattering device (DLS7000 manufactured by Otsuka Electronics Co., Ltd.). FIG. 2 shows the results. At 25 ° C. or less, the particle diameter was 10 nm or less, but at 30 ° C. or more, the particle diameter became about 250 nm, and it became clear that the polymer was aggregated. Therefore, it was confirmed that the phase transition temperature was around 25 ° C. even in this method.
[0027]
-Examples 2 to 4
In Examples 2 to 4, polymers were produced under the same conditions as in Example 1 except that the amounts of 5-aminopentanol and 6-aminohexanol used were changed. Table 1 shows the results of the polymer yield, number average molecular weight, molecular weight distribution, and phase transition temperature of each condition together with the results of Example 1.
[0028]
[Table 1]

[0029]
In each case, the obtained polymers had the composition ratios according to the charge ratios. FIG. 3 shows the phase transition behavior of the polymers obtained in Examples 2 to 4 when the temperature was raised. All of the polymers showed a sharp temperature response, and the phase transition temperature increased as the amount of 5-aminopentanol introduced increased.
[0030]
-Comparative Example 1-
5-aminopentanol (1.04 g, 10.0 mmol) instead of 5-aminopentanol (0.52 g, 5.0 mmol) and 6-aminohexanol (0.59 g, 5.0 mmol) A polymer was produced under the same conditions as in Example 1 except for the above. The obtained aqueous solution of the polymer did not show a phase transition at 0 to 100 ° C.
[0031]
-Comparative Example 2-
Except that instead of 5-aminopentanol (0.52 g, 5.0 mmol) and 6-aminohexanol (0.59 g, 5.0 mmol), 6-aminohexanol (1.18 g, 10.0 mmol) was used. Produced a polymer under the same conditions as in Example 1. The resulting polymer did not dissolve in water at 0-100 ° C.
[0032]
Example 5
[Preparation of gel]
Instead of 5-aminopentanol (0.52 grams, 5.0 mmol) and 6-aminohexanol (0.59 grams, 5.0 mmol), 4-aminobutanol (5.0 mmol) and 5-aminopentanol ( A polymer was produced under the same conditions as in Example 1 except that the amount was changed to 5.0 mmol). 0.6 g of this polymer and 45 μL (10 mol%) of 1,6-hexane diisocyanate were dissolved in 3 mL of N, N-dimethylformamide. This solution was sealed between two plates (material: tetrafluoroethylene polymer) having an interval of 3 mm to form a liquid film. The reaction was allowed to proceed at 60 ° C. for 24 hours, followed by washing with pure water to quantitatively obtain a gel.
[0033]
[Measurement of swelling degree]
This gel was kept in water at a predetermined temperature of 5 ° C to 70 ° C for 5 hours to swell. The swelled gel was taken out and weighed, and the ratio to the weight when dried was defined as the swelling degree. FIG. 4 shows the temperature response of the degree of swelling. The gel swelled about 8 times up to 20 ° C., but the degree of swelling decreased as the temperature was raised. From this, it was clarified that the present gel exhibited temperature responsiveness.
[0034]
[Slow release evaluation]
The gel of Example 5 was immersed in a 0.2% aqueous solution of Brilliant Blue FF for one week, and then the Brilliant Blue FF attached to the surface was thoroughly washed with water. This brilliant blue FF-containing gel was immersed in water at a predetermined temperature, and the amount of leaked brilliant blue FF was determined from a change in absorbance at a wavelength of 630 nm using a UV-visible spectrophotometer. FIG. 5 shows the results. Release of Brilliant Blue FF at 50 ° C. was found to be faster than 30 ° C. This is because, as shown in FIG. 4, the release of Brilliant Blue FF was accelerated at 50 ° C. due to the contraction of the gel. From this result, it was clarified that the present gel can control the sustained release property depending on the temperature.
[0035]
【The invention's effect】
The thermoresponsive polymer and thermoresponsive gel of the present invention are biodegradable because they are based on polyamino acids. Further, since the temperature-responsive polymer has a modifiable hydroxyl group in the side chain, various functions can be achieved. Therefore, the temperature-responsive polymer and the temperature-responsive gel of the present invention are extremely useful as a drug sustained release material, a mechanochemical material, a temperature sensor, a separation membrane, a water retention agent and the like.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the transmittance of a polymer solution of Example 1 and temperature.
FIG. 2 is a graph showing the relationship between the particle size of the polymer in the polymer solution of Example 1 and the temperature.
FIG. 3 is a graph showing the relationship between the transmittance of each polymer solution of Examples 1 to 4 and temperature.
FIG. 4 is a graph showing the relationship between the degree of swelling and the temperature of the gel of Example 5.
FIG. 5 is a graph showing sustained release of a drug by the gel of Example 5.

Claims (9)

A temperature responsiveness comprising a random copolymer comprising a repeating unit (A) represented by the following general formula (1) and a repeating unit (B) represented by the following general formula (2) as constituent components. polymer.

(In the formula, R ¹ represents a hydroxyalkyl group, and R ² represents a hydroxyalkyl group, an alkyl group, or an aryl group different from R ^1. ) R ¹ is ^{one selected} from a 4-hydroxybutyl group, a 5-hydroxypentyl group and a 6-hydroxyhexyl group; R ² is a 3-hydroxypropyl group, a 4-hydroxybutyl group, a 5-hydroxypentyl group; The temperature-responsive polymer according to claim 1, which is one selected from a -hydroxyhexyl group, a methyl group, an ethyl group, an n-propyl group, and an i-propyl group. The temperature-responsive polymer according to claim 1 or 2, wherein the molar composition ratio of the repeating units (A) and (B) is from 95: 5 to 5:95. The temperature-responsive polymer according to any one of claims 1 to 3, wherein the number average molecular weight is in the range of 1,000 to 1,000,000. R ¹ is a hydroxyalkyl group, ^{when R 2} denote the ^{R 1} different from hydroxyalkyl group, an alkyl group or an aryl group, mixing ^{polysuccinimide} the R 1 NH ₂ and ^R 2 NH ₂ in an organic solvent A method for producing a temperature-responsive polymer, comprising: The fact that a random copolymer having a repeating unit (A) represented by the following general formula (1) and a repeating unit (B) represented by the following general formula (2) as constituents was crosslinked with a polyfunctional compound. Characterized temperature-responsive gel.

(In the formula, R ¹ represents a hydroxyalkyl group, and R ² represents a hydroxyalkyl group, an alkyl group, or an aryl group different from R ^1. ) The temperature-responsive gel according to claim 6, wherein the polyfunctional compound is a diisocyanate. The temperature-responsive gel according to claim 6, wherein the polyfunctional compound is α, ω-alkylene diisocyanate. A drug sustained-release material comprising the temperature-responsive gel according to claim 6.

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