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"Material polimer untuk menyusun hidrogel harus dapat mengembang (swell) dan mempertahankan fraksi air pada strukturnya, namun tidak larut dalam air. Polimer alami memiliki gugus fungsi yang dapat menjadi pusat aktif reaksi dimana dapat dilakukan modifikasi untuk menghasilkan suatu polimer dengan karakteristik yang lebih baik. Kitosan merupakan polimer alami yang memiliki kekuatan struktur yang kurang dibandingkan kemampuan swelling. Sintesis hidrogel kitosan dengan metode full interpenetrating polymer network (IPN) dapat meningkatkan kekuatan struktur melalui ikat silang. Tahap pertama adalah sintesis jaringan polimer kitosan terikat silang asetaldehida. Tahap kedua adalah sintesis jaringan polimer PNVCL terikat silang N, N?-metilenbisakrilamida (MBA) melalui polimerisasi radikal bebas monomer NVCL dengan inisiator amonium persulfat (APS). Variasi waktu, rasio kitosan-PNVCL, konsentrasi agen pengikat silang, dan konsentrasi inisiator dipelajari untuk mengetahui kondisi optimum. Kondisi optimum diperoleh pada reaksi 2 jam dengan rasio kitosan/NVCL 90:10 (b/b %), konsentrasi MBA 0,5%, dan konsentrasi APS 3%. HSA kitosan-PNVCL memberikan rasio swelling 380,66% dan derajat ikat silang 60,85%. Karakterisasi HSA dilakukan dengan spektrofotometer Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), dan X-Ray Diffraction (XRD).

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Polymer material used for hydrogel should have the ability to swell and to keep water molecules in its structure without dissolving in water. Natural polymers has functional groups which can perform as active sites in modification to produce polymer with better characteristic. Chitosan is a natural polymer which has good swelling ability but lack of structural strength. Synthesis of chitosan hydrogel by interpenetrating polymer network (IPN) will increase its strength through crosslinking. In this research, the first step of modification was the synthesis of chitosan polymer network crosslinked by acetaldehyde. The next step was the synthesis of PNVCL polymer network crosslinked by N,N-methylbisacrylamide (MBA) through free radical polymerization of NVCL monomer with ammonium persulfat (APS) as the initiatior. Optimum reaction time, chitosan/PNVCL ratio (w/w %), concentration of crosslinker agent, and concentration of initiator had been observed. The optimum conditions were obtained as followed: 2 hours reaction, the ratio chitosan/PNVCL of 90:10 (w/w %), %-w MBA concentration of 0,5%, and APS concentration of 3%. The swelling ratio of the hydrogel was 380,66% while the crosslinking degree was 60,85%. Fourier transfor infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), and X-Ray diffraction (XRD) were used for the characterization of the hydrogel."

"Metode IPN (Interpenetrating Polymer Network) baik semi maupun full IPNdapat digunakan untuk mensintesis hidrogel superabsorben (HSA) kitosan dan poli(N-vinil-kaprolaktam) (PNVCL) atau HSA kitosan-PNVCL. Pada metode full IPN jaringan polimer disintesis secara bertahap (sequential). Tahap pertama adalah sintesis jaringan polimer kitosan terikat silang asetaldehida dan homogenisasi dengan monomer N-vinil-kaprolaktam (NVCL) Tahap kedua adalah sintesis jaringan polimer PNVCL terikat silang N Nmetilenbisakrilamida (MBA) melalui polimerisasi radikal bebas monomer NVCL dengan inisiator amonium persulfat (APS) Hasil sintesis HSA kitosan-PNVCL full-IPN memiliki kekuatan struktur ikat silang dan kemampuan swelling yang baik Kekuatan struktur ikat silang meningkat dengan bertambahnya waktu reaksi, konsentrasi agen pengikat silang, inisiator, dan dipengaruhi rasio kitosan-PNVCL Kemampuan swelling HSA kitosan-PNVCL dengan kekuatan struktur ikat silang yang baik didapat pada rasio kitosan/PNVCL 70:30 (b/b %). HSA kitosan-PNVCL full-IPN memberikan persen derajat ikat silang yang tinggi (78,2%) dan kemampuan swelling yang baik (390,2%) Karakterisasi.

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The IPN (Interpenetrating Polymer Network) method, both semi and full IPN, can be used to synthesize chitosan and poly (N-vinyl-caprolactam) (PNVCL) superabsorbent hydrogels or HSA chitosan-PNVCL. In the full method of IPN polymer networks are synthesized sequentially. The first stage is the synthesis of crosslinked acetaldehyde chitosan polymer tissue and homogenization with N-vinyl-caprolactam (NVCL) monomer The second stage is synthesis of PNVCL polymer network bound by N Nmetilenbisakrilamida (MBA) through NVCL monomer free polymerization with ammonium persulfate (APS) initiator Synthesis of HSA chitosan-PNVCL full-IPN has crosslinked structure strength and good swelling ability The strength of crosslinking structure increases with increasing reaction time, concentration of crosslinking agent, initiator, and influenced by chitosan-PNVCL ratio Swelling ability of HSA chitosan-PNVCL with good cross-link structure strength is obtained at the chitosan / PNVCL ratio of 70:30 (b / b%). Full-IPN HSA chitosan-PNVCL gives a high percentage of crosslinking (78.2%) and good swelling ability (390.2%) Characterization Characterization."

"Metode semi-Interpenetrating Polymer Network (Semi-IPN) merupakan salah satu metode untuk mensintesis hidrogel. Pada metode semi-IPN, kitosan mengalami ikat silang dengan agen pengikat silang asetaldehida/ formaldehida/ glutaraldehida membentuk jaringan polimer kitosan terikat silang yang kemudian berinteraksi dengan polimer metil selulosa yang berbentuk linier. Umumnya derajat ikat silang dan rasio swelling hidrogel semi-IPN akan dipengaruhi oleh waktu reaksi, rasio komposisi kitosan-metil selulosa, dan jenis agen pengikat silang yaitu asetaldehida, formaldehida, dan glutaraldehida. Kemampuan swelling dan derajat ikat silang hidrogel kitosan-metil selulosa semi-IPN yang optimum didapat pada rasio kitosan/metil selulosa 60:40 (b/b), agen pengikat silang formaldehida 2% (b/b), dan waktu reaksi 3 jam yaitu persen rasio swelling 785,6 % dan derajat ikat silang 50,8 %. Hidrogel kitosan-metil selulosa dengan metode semi-IPN memiliki rasio swelling dan derajat ikat silang lebih besar dibandingkan dengan hidrogel kitosan nonkovalen. Karakterisasi hidrogel kitosan-metil selulosa semi-IPN dilakukan dengan instrumen Fourier Transfrom Infra Red (FTIR), Differential Scanning Calorimetry (DSC), dan Scanning Electron Microscope (SEM).

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Semi-Interpenetrating Polymer Network (semi-IPN) method is one of many methods which used to synthesize hydrogels. In semi-IPN method, chitosan was crosslinked with crosslinking agent acetaldehyde/ formaldehyde/ glutaraldehyde to form crosslinked chitosan polymer network that will interracts with methyl cellulose polymer which have linear form. In general, degree of crosslinking and swelling ratio of semi-IPN hydrogels were influenced by reaction time, composition ratio of chitosan-methyl cellulose, and crosslinking agent acetaldehyde, formaldehyde, and glutaraldehyde. Swelling ability and degree of crosslinking of chitosan-methyl cellulose hydrogel with semi-IPN method optimally reach at chitosan/methyl cellulose ratio 60:40 (b/b) with formaldehyde crosslinking agent in 3 hours reaction time is 785,6 % swelling ratio and 50,8 % degree of crosslinking. Chitosan-methyl cellulose hydrogel with semi-IPN method has higher swelling ratio and degree of crosslinking compared to noncovalent chitosan hydrogel. Characterization of chitosan-methyl cellulose semi-IPN hydrogel using Fourier Transfrom Infra Red (FTIR), Differential Scanning Calorimetry (DSC), dan Scanning Electron Microscope (SEM) instrument."

"Sintesis hidrogel kitosan-poli(N-vinil-2-pirolidon) (PNVP) dengan metode full-Interpenetrating Polymer Network (full-IPN) dilakukan secara bertahap (sequential). Tahap pertama yaitu melakukan sintesis jaringan polimer kitosan terikat silang asetaldehida melalui homogenisasi. Tahap kedua yaitu melakukan sintesis jaringan PNVP terikat silang N, N?-metilenbisakrilamida (MBA) melalui reaksi polimerisasi radikal bebas dari monomer NVP dengan agen pengikat silang MBA dan inisiator amonium persulfat (APS). Hidrogel kitosan-PNVP full-IPN yang dihasilkan, memiliki kekuatan ikat silang lebih baik yang teramati dari nilai derajat ikat silang serta dapat mempertahankan kemampuan swelling dengan baik yang teramati dari nilai rasio swelling dibandingkan dengan hidrogel kitosan.Hasil optimum dari rasio swelling dan derajat ikat silang pada hidrogel kitosan-PNVP full-IPN sebesar 149,8% dan 85,4% dengan komposisi kitosan:monomer NVP yaitu 70:30 (b/b %), waktu reaksi polimerisasi 0,5 jam, konsentrasi MBA 1% (b/b), serta konsentrasi APS 1% (b/b). Karakterisasi dilakukan dengan Spektrofotometer Fourier Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC), dan Scanning Electron Microscope (SEM).

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Synthesis of hydrogel chitosan-poly(N-vinyl-2-pyrrolidone) (PNVP) by full-Interpenetrating Polymer Network was performed in stages (sequential method). The first stage was the synthesis of chitosan polymer network by crosslinked with acetaldehyde under homogenization process. The second stage was the synthesis which was PNVP of crosslinked with N,N?-methylenebisacrylamide (MBA) through free radical polymerization reaction of NVP monomer, was used as the crosslink agent MBA and ammonium persulfate (APS) as the initiator. The synthesized hydrogel chitosan-PNVP full-IPN has a good strength due to the observed crosslinking structure observed the value of crosslinking degree and the good swelling capability by the value of swelling ratio compared with hydrogel chitosan.

The optimum result of swelling ratio and the degree of crosslinking from hydrogel chitosan-PNVP full-IPN were 149,8% and 85,4% which were obtained with the composition chitosan:NVP monomer of 70:30 (w/w %), the polymerization reaction time of 0,5 hours, the concentration MBA 1% (w/w), and the concentration APS 1% (w/w). Products characterizations were done by Fourier Transform Infrared Spectrophotometer (FTIR), Differential Scanning Calorimetry (DSC), dan Scanning Electron Microscope (SEM)."

"Metode semi interpentrating polymer network (semi-IPN) merupakan metode yang digunakan untuk mensintesis hidrogel kitosan-poliNNDMAA. Pada metode ini, jaringan kitosan akan terikat silang dengan agen ikat silang lalu berinteraksi dengan jaringan polimer NNDMAA secara linear. Hasil sintesis memperlihatkan bahwa variasi penambahan monomer NNDMAA, agen ikat silang dan waktu reaksi akan menurunkan daya swelling dan meningkatkan derajat ikat silang. Rasio swelling dan derajat ikat silang optimum hidrogel kitosan poli NNDMAA semi-IPN terikat silang formaldehida didapatkan sebesar 545,64% dan 75,02% pada penambahan 25% berat NNDMAA dan waktu optimum pada 2 jam. Hidrogel kitosan poli NNDMAA semi-IPN terikat silang formaldehida memilki derajat ikat silang yang lebih besar jika dibandingkan terikat silang glutaraldehida maupun asetaldehida. Karakterisasi dilakukan dengan spektrofotometer Fourier Transform Infra Red (FTIR), Differential Scanning Calotimetry(DSC) dan Scanning Electron Microscope (SEM).

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Method semi interpentrating polymer network (semi-IPN) is a method used to synthesize the chitosan hydrogel-poliNNDMAA. In this method, chitosan will crosslinked with a crosslink agent then interacts with the polymer network NNDMAA linearly. Synthesis results show that the variation of the addition of monomer NNDMAA, crosslink agents and reaction time will reduce swelling and increase the degree of crosslink. Swelling ratio and the degree of crosslink optimum chitosan hydrogel poly NNDMAA crosslinked semi-IPN formaldehyde obtained by 545.64% and 75.02% on addition of 25% by weight NNDMAA and optimum time at 2 hours. Chitosan hydrogel poly NNDMAA crosslinked semi-IPN formaldehyde have the degree of cross belt larger than glutaraldehyde cross-linked or acetaldehyde. Characterization is done by spectrophotometer Fourier Transform Infra Red (FTIR), Differential Scanning Calotimetry (DSC) and Scanning Electron Microscope (SEM)."

"Hidrogel kitosan termodifikasi interpenetrating polymer network berhasil disintesis yaitu kitosan, kitosan terikat-silang, kitosan-poly N-vinyl-2-pyrrolidone semi-IPN dan kitosan-N-vinyl-2-pyrrolidone full-IPN. Hidrogel kitosan termodifikasi interpenetrating polymer network diloadingkan captopril. Metode loading obat ke dalam matriks hidrogel yaitu in situ and post loading. Konsentrasi obat yang terloading ke dalam matriks hidrogel divariasikan yaitu 12.5 mg; 25 mg; 37.5 mg and 50 mg. Loading obat dengan metode in situ loading dilakukan dengan menambahkan obat sebelum penambahan agen pengikat silang, sedangkan post loading dilakukan dengan mengimersikan hidrogel ke dalam larutan obat. hidrogel yang terloading obat disebut mikrokapsul. Efisiensi enkapsulasi ditentukan dengan mengimeriskan mikrokapsul ke dalam larutan buffer pH 7,4. Hidrogel dikarakterisasi dilakukan dengan penentuan derajat ikat-silang , rasio swelling , spketrofotometer FTIR dan mikroskop stereo. Derajat ikat-silang dari kitosan, kitosan terikat-silang, kitosan-poly N-vinyl-2-pyrrolidone semi-IPN dan kitosan-N-vinyl-2-pyrrolidone full-IPN adalah 51.62 , 54.65 , 70.15 dan 77.23 . rasio swelling dari kitosan, kitosan terikat-silang, kitosan-poly N-vinyl-2-pyrrolidone semi-IPN dan kitosan-N-vinyl-2-pyrrolidone full-IPN adalah 4412.88 , 2118.01 , 1748.65 dan 441,38 selama 1 jam. Konsentrasi optimum loading obat 12.5 mg and 25 mg. Hidrogel terloading obat disebut mikrokapsul. Pelepasan mikrokapsul captopril in situ and post loading selama 12 jam menunjukkan pelepasan lambat. Profil pelepasan obat pada pH 1,2 dari matriks hidrogel kitosan dan kitosan terikat-silang in situ loading secara difusi dan degradasi, sedangkan semi-IPN and full-IPN in situ loading secara difusi, pada pH 7,4 pelepasan obat mikrokapsul in situ loading secara difusi. Profil pelepasan obat dari mikrokaspul post loading pada pH 1,2 dan 7,4 terjadi secara difusi diikuti erosi matriks hidrogel.

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Preparation chitosan interpenetrating polymer network modified hydrogels have been successfuly. It were chitosan, chitosan crosslinked, semi IPN chitosan poly N vinyl 2 pyrrolidone and full IPN chitosan N vinyl 2 pyrrolidone. These hydrogels were loaded by captropil. Captopril was loaded within hydrogel matrix using both in situ and post loading method. Concentration variation of drug loaded were 12.5 mg 25 mg 37.5 mg and 50 mg. At in situ loading, drug was loaded during synthesis of hydrogel before the addition of crosslinking agent, while at post loading method hydrogels were immersed into a drug solution. This hydrogels loaded captopril called microcapsul. Encapsulation efficiency was evaluated in pH 7.4 solution. Hydrogels characterization including crosslinking degree , swelling ratio , FTIR spectrophotometer and stereo microscope. Crosslinking degree of chitosan, chitosan crosslinked, semi IPN and full IPN hydrogels were found to be 51.62 , 54.65 , 70.15 and 77.23 respectively. Swelling ratio of chitosan, chitosan crosslinked, semi IPN and full IPN hydrogels were 4412.88 , 2118.01 , 1748.65 and 441,38 for 1 hour, respectively. The optimum drug concenration was 12.5 mg and 25 mg. Hydrogels loading drug called microcapsule. Release of captopril microcapsules by in situ and post loading shown that slow release for 12 hour. Profile of release drug from chitosan and chitosan crosslinked hydrogels by in situ loading at pH 1,2 through difussion and degradation, while semi IPN and full IPN hydrogels by in situ loading at pH 1,2 through difussion. At pH 7,4 of profile of release drug from microcapsules through difussion. Profile of release drug at pH 1,2 and 7,4 from microcapsules by post loading through difussion followed erotion."

"Untuk meningkatkan efektifitas penggunaan pupuk pada media tanam, dilakukan modifikasi terhadap pupuk sehingga menjadi pupuk lepas lambat. Dalam penelitian ini, pupuk NPK yang disintesis mengandung urea, amonium dihidrogen fosfat, dan kalium dihidrogen fosfat. Enkapsulasi pupuk NPK menggunakan hidrogel semi interpenetrating polymer network (semi-IPN) berbasis kitosan dan polistirena dilakukan dengan metode in situ loading dan post loading. Komposisi hidrogel kitosan-polistirena semi-IPN yang digunakan terdiri dari kitosan : stirena yaitu 80:20 dan menggunakan agen pengikat silang 5% asetaldehid 0,1 M. Karakterisasi pembentukan hidrogel kitosan-polistirena semi-IPN dan hidrogel kitosan dilakukan menggunakan spektorfotometri Fourier Tramsform Infrared (FTIR) dan mikroskop stereo. Uji pendahuluan seperti rasio sweliing dan derajat ikat silang juga diselidiki. Efisiensi laoding pupuk NPK dengan metode in situ loading mencapai 92.96% lebih besar daripada metode post loading yaitu 48.91% diukur dengan menggunakan spektrofotometer UV-Vis. Studi pelepasan pupuk NPK dari matriks hidrogel kitosan-polistirena semi-IPN dilakukan secara gravimetric dan spektrofotometri. Hasil uji pelepasan pupuk NPK yang terenkapsulasi dalam matriks hidrogel secara in situ loading lebih rendah dibandingkan secara post loading. Sifat lepas lambat dan kemampuan retensi air yang baik menunjukkan bahwa hidrogel kitosan-polistirena semi-IPN terenkapsulasi NPK berpotensi untuk aplikasi di bidang pertanian sebagai material pembawa pupuk.

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To improve the effectiveness of the use of fertilizer in the planting medium, the modification of the fertilizer was conducted to achieve a slow-release fertilizer. In this study, NPK fertilizer which contain urea, ammonium dihydrogen phosphate, and potassium dihydrogen phosphate was prepared. Encapsulation of NPK fertilizer using the semi-interpenetrating polymer network (semi-IPN) and polystyrene-based chitosan hydrogels was conducted using in situ loading and post-loading. The semi-IPN chitosan-polystyrene hydrogels were composed of chitosan: styrene monomer with 80:20 ratio and 5% acetaldehyde 0.1 M has been used as crosslinking agent. Characterization of semi-IPN chitosan-polystyrene hydrogels and chitosan hydrogels has been done using Fourier Transform Infrared (FTIR) Spectroscopy and stereo microscope. Preliminary test such as sweliing ratio and the degree of crosslinking was also investigated. Efficiency Laoding NPK fertilizer with in situ loading method was found to be 92.96% which was greater than the post-loading method which 48.91% . the efficiency loading wasmeasured by using UV-Vis spectrophotometer. Study of NPK fertilizer release from the chitosan hydrogel matrix semi-IPN-polystyrene was determined by gravimetric and spectrophotometric methods. Release of NPK fertilizer encapsulated within a hydrogel matrix by in situ loading was found to be lower than in post loading. Slow-release property and good water retention capability indicates that the chitosan-polystyrene hydrogel semi-IPN encapsulated NPK has apotential for applications in agriculture as a fertilizer carrier material."

"Bromelain memiliki waktu paruh yang singkat sehingga enzim ini akan cepat dieliminasi oleh tubuh. Enkapsulasi bromelain menggunakan polimer biodegradable sebagai pengantar obat terkontrol dapat meminimalkan masalah tersebut. Pada penelitian ini, enkapsulasi bromelain menggunakan hidrogel full interpenetrating polymer network full-IPN berbasis pada kitosan dan n-vinilkaprolaktam telah dilakukan metode post-loading. Komposisi hidrogel full-IPN terdiri dari kitosan : n-vinilkaprolaktam 90:10 b/b , asetaldehid 0,1 M 2 b/b dan MBA 0,5 M b/b terhadap kitosan sebagai agen pengikat silang. Karakterisasi hidrogel full-IPN menggunakan spektrofotometer UV-Vis, spektrofotometer FTIR, dan mikroskop stereo. Efisiensi loading bromelain dengan metode post-loading mencapai 98 diukur dengan spektrofotometer UV-Vis. Profil pelepasan bromelain memiliki pelepasan rata-rata pada pH 1,2 selama 2 jam 81 post-loading dan pelepasan rata-rata dengan pH 7,4 selama 8 jam 97 post-loading. Aktivitas proteolitik, kadar protein, dan aktivitas spesifik pada bromelain diperoleh dengan nilai terbaik masing-masing sebesar 0,116 Unit, 0,145 mg, dan 0,8 Unit/mg.

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Bromelain has a short half life so that this enzyme will quickly be eliminated by the body. Encapsulation of bromelain using biodegradable polymers as controlled drug delivery can minimize the problem. In this study, bromelain encapsulation using full interpenetrating polymer network full IPN hydrogel based on chitosan and n vinylcaprolactam has been done post loading method. The full IPN hydrogel composition comprises chitosan n vinylcaprolactam 90 10 w w, acetaldehyde 0.1 M 2 w w and MBA 0.5 M w w to chitosan as a crosslinking agent. Full IPN hydrogel characterization using UV Vis spectrophotometer, FTIR spectrophotometer, and stereo microscope. The efficiency of bromelain loading by post loading method was 98 measured by UV Vis spectrophotometer. The bromelain release profile has the average release at pH 1.2 for 2 hours 81 post loading and average release with pH 7.4 for 8 hours 97 post loading. Proteolytic activity, protein levels, and specific activity on bromelain were obtained with the best values of 0,116 Units 0,145 mg and 0,8 Units mg, respectively."

"Bromelain memiliki waktu paruh yang singkat sehingga enzim ini akan cepat dieliminasi oleh tubuh. Enkapsulasi bromelain menggunakan polimer biodegradable sebagai pengantar obat terkontrol dapat meminimalkan masalah tersebut. Pada penelitian ini, enkapsulasi bromelain menggunakan hidrogel full interpenetrating polymer network full-IPN berbasis pada kitosan dan n-vinilkaprolaktam telah dilakukan metode post-loading. Komposisi hidrogel full-IPN terdiri dari kitosan : n-vinilkaprolaktam 90:10 b/b , asetaldehid 0,1 M 2 b/b dan MBA 0,5 M b/b terhadap kitosan sebagai agen pengikat silang. Karakterisasi hidrogel full-IPN menggunakan spektrofotometer UV-Vis, spektrofotometer FTIR, dan mikroskop stereo. Efisiensi loading bromelain dengan metode post-loading mencapai 98 diukur dengan spektrofotometer UV-Vis. Profil pelepasan bromelain memiliki pelepasan rata-rata pada pH 1,2 selama 2 jam 81 post-loading dan pelepasan rata-rata dengan pH 7,4 selama 8 jam 97 post-loading. Aktivitas proteolitik, kadar protein, dan aktivitas spesifik pada bromelain diperoleh dengan nilai terbaik masing-masing sebesar 0,116 Unit, 0,145 mg, dan 0,8 Unit/mg.

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Bromelain has a short half life so that this enzyme will quickly be eliminated by the body. Encapsulation of bromelain using biodegradable polymers as controlled drug delivery can minimize the problem. In this study, bromelain encapsulation using full interpenetrating polymer network full IPN hydrogel based on chitosan and n vinylcaprolactam has been done post loading method. The full IPN hydrogel composition comprises chitosan n vinylcaprolactam 90 10 w w, acetaldehyde 0.1 M 2 w w and MBA 0.5 M w w to chitosan as a crosslinking agent. Full IPN hydrogel characterization using UV Vis spectrophotometer, FTIR spectrophotometer, and stereo microscope. The efficiency of bromelain loading by post loading method was 98 measured by UV Vis spectrophotometer. The bromelain release profile has the average release at pH 1.2 for 2 hours 81 post loading and average release with pH 7.4 for 8 hours 97 post loading. Proteolytic activity, protein levels, and specific activity on bromelain were obtained with the best values of 0,116 Units 0,145 mg and 0,8 Units mg, respectively."

"Hidrogel semi-IPN merupakan suatu jaringan polimer yang memiliki kemampuan menyerap air yang besar dan cenderung mempertahankan strukturnya. Sintesis hidrogel kitosan-polistirena dengan metode semi-IPN dilakukan dengan dua tahap. Pada tahap pertama dibentuk jaringan kitosan terikat silang dengan menggunakan variasi agen pengikat silang yaitu, asetaldehida, formaldehida, dan glutaraldehida. Pada tahap kedua dilakukan polimerisasi polistirena di dalam jaringan kitosan terikat silang. Kondisi optimum dalam sintesis hidrogel kitosan-polistirena semi-IPN diperoleh dengan waktu reaksi polimerisasi polistirena selama 4 jam, komposisi kitosan dan stirena sebesar 80:20, dan agen pengikat silang asetaldehida. Pada kondisi optimum, hidrogel kitosan-polistirena semi-IPN memiliki sifat mekanik yang lebih baik dibandingkan dengan hidrogel kitosan dan mampu mempertahankan kemampuan swelling yang baik. Nilai rasio swelling dan derajat ikat silang hidrogel kitosan-polistirena semi-IPN pada kondisi optimum sebesar 751,2% dan 24,1% secara berurutan. Karakterisasi hidrogel kitosan-polistirena semi-IPN dilakukan dengan spektrofotometer Fourier Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC), dan Scanning Electron Microscope (SEM).

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Semi-IPN hydrogel is a polymer network that has a great ability to absorb water and tend to maintain its structure. Synthesis of hydrogel chitosan -polystyrene by semi-IPN method performed by two steps. First step, chitosan crosslinked network formed by using a variety of crosslinking agents, namely acetaldehyde, formaldehyde, and glutaraldehyde. In the second step, polymerization polystyrene in chitosan crosslinked network. The optimum conditions in synthesis of chitosan hydrogel-polystyrene semi-IPN is obtained with a reaction time of polymerization of polystyrene for 4 hours, composition of chitosan and styrene is 80:20, and the crosslinking agent is acetaldehyde. At the optimum conditions, hydrogel chitosan- polystyrene semi-IPN has better mechanical properties compared with the chitosan hydrogel and able to maintain good swelling capability. The value of swelling ratio and the degree of crosslinking of hydrogel chitosan-polystyrene semi-IPN in optimum condition are 751.2% and 24.1%. Characterization of hydrogel chitosan-polystyrene semi-IPN has been done by Spectrophotometer Fourier Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscope (SEM)."