Functional Particles
Supporting Diagnostics
We develop, manufacture and supply raw materials for in vitro diagnostic reagents, handled in-house from development through to manufacturing and sales.
Products
We supply polymer particles designed around particle size, surface charge and function to meet the performance required of in vitro diagnostic reagents.
Latex particles
Polystyrene nanoparticles for immunoturbidimetry. Particle size and COOH charge density are designed for each application.
Magnetic particles
Magnetic particles for chemiluminescent immunoassay, supporting direct antibody coupling and streptavidin (SA) immobilisation.
Coloured and fluorescent particles
Coloured and fluorescent latex particles for POCT and lateral flow assays.
Why ZOKK
Particle design for each application
We design and develop particles with appropriate sizes and surface characteristics, taking into account the intended application, assay principle and instrument characteristics of in vitro diagnostic and research reagents.
Integrated support from development to mass production
Product design, synthesis, performance evaluation, process development, quality assessment and scale-up are all handled in house, from early development through commercial production.
Experience in in vitro diagnostics
We bring practical knowledge and experience in developing and manufacturing raw materials for latex immunoturbidimetry, chemiluminescence and POCT.
Custom development and OEM
Alongside our standard products, we welcome enquiries about custom development, prototyping and OEM based on your application and specifications.
Company
We provide consistent quality built on proven technology, together with flexible development support tailored to each application, at a competitive price. Through the development, manufacture and sale of raw materials used in in vitro diagnostic and research reagents, we contribute to progress in healthcare and research.
As diagnostics and research move further towards automation, the performance and quality demanded of reagents and their raw materials continue to rise. We respond to these varied requirements through product design and technical development that reflect each application and instrument.
| Company name | ZOKK Co., Ltd. / ゾック株式会社 |
|---|---|
| Founded | 3 June 2024 |
| Capital | JPY 10 million |
| Employees | 8 (as of July 2026) |
| Business | Development, manufacture and sale of raw materials for in vitro diagnostic reagents; OEM |
| Address | Room 601, Tokatsu Techno Plaza, 5-4-6 Kashiwanoha, Kashiwa, Chiba, Japan |
Careers
We are hiring R&D and manufacturing engineers, as well as support and administrative staff. If you are interested, please send us your CV by email.
Open positionsContact
We welcome enquiries about product specifications and technical questions, samples and quotations, OEM and custom development, and new business relationships.
Contact usCompany
Consistent quality built on proven technology, with flexible development support, at a competitive price.
Message
Since its establishment in 2024, ZOKK Co., Ltd. has focused on the development of nanoparticle raw materials for in vitro diagnostics.
Building on our polymerisation technology, we are engaged in the integrated research, development and mass production of carrier materials used in medical diagnostics, including latex particles, magnetic beads and filler particles. We provide IVD companies in Japan and abroad with raw material solutions that combine consistent quality with strong cost competitiveness.
Medical diagnostics play an important role in protecting human life and health. Carrier materials form the foundation for the development of high-quality diagnostic reagents.
At our approximately 280 m² research and development facility, we strictly control particle size, surface functional groups and batch-to-batch consistency through established polymerisation processes and a comprehensive performance verification system. Through these quality control measures, ZOKK’s magnetic beads and latex particles deliver consistent quality and performance across a range of clinical testing applications, including chemiluminescence immunoassays, immunoturbidimetry and point-of-care testing.
We aim to be more than a raw material supplier — a technology partner that works closely with our customers. In response to the performance requirements of various diagnostic kits, we provide customised particle modification services as well as OEM reagent development and manufacturing services, while continuously improving our manufacturing processes and optimising product performance.
Looking ahead, ZOKK will continue to advance its nano-biomaterial technologies and expand their applications, developing more reliable and versatile raw materials for diagnostic use.
We remain committed to providing products that earn the trust of our customers and, together with IVD industry partners in Japan and abroad, to contributing to the advancement of clinical testing technologies and the improvement of human health.
Kejun Fan
| Company name | ZOKK Co., Ltd. / ゾック株式会社 |
|---|---|
| Founded | 3 June 2024 |
| Capital | JPY 10 million |
| Employees | 8 (as of July 2026) |
| Business | Development, manufacture and sale of raw materials for in vitro diagnostic reagents; OEM |
| Technology | Polymerisation technology and reagent development know-how |
| Address | Room 601, Tokatsu Techno Plaza 5-4-6 Kashiwanoha, Kashiwa Chiba 277-0882, Japan |
| Phone | +81-4-7128-7017 |
| zokk@zokkbio.com |
Technology
We occupy approximately 280 m² at Tokatsu Techno Plaza, comprising office space and areas for R&D and production. With the equipment required for aqueous polymerisation and experienced engineers on site, we cover the full path from development through manufacturing and evaluation.
Emulsion polymerisation (batch, incremental and seed) is our core technology. Aqueous solution polymerisation is used for water-soluble polymers, while two-step swelling and suspension polymerisation are used to design and produce polymer particles with the size and size distribution each application requires.
Access
- Address
- Room 601 (6F), Tokatsu Techno Plaza, 5-4-6 Kashiwanoha, Kashiwa, Chiba 277-0882, Japan
- Nearest bus stop
- “National Cancer Center” (Tobu Bus), about 5 minutes on foot
- Nearest station
- Kashiwanoha-campus Station, Tsukuba Express (about 6–11 minutes by bus from the west exit)
Access information on the Tokatsu Techno Plaza website (Japanese)View on Google Maps
By train and bus
| Kashiwanoha-campus Sta. (Tsukuba Express), west exit | Tobu Bus bound for “National Cancer Center”, “Todai-nishi” or “Edogawadai Sta. East Exit”, about 6–11 min |
|---|---|
| JR Kashiwa Sta. (Joban Line), west exit | Tobu Bus bound for “National Cancer Center”, about 25 min (last stop) |
| Edogawadai Sta. (Tobu Urban Park Line), east exit | Tobu Bus bound for “Kashiwanoha-campus Sta. West Exit (via National Cancer Center)”, about 11 min |
| Haneda Airport | Airport limousine bus to “National Cancer Center”, about 65–75 min |
In all cases, get off at the “National Cancer Center” bus stop; the building is about 5 minutes on foot.
By car
| Kashiwa IC, Joban Expressway | About 5 min |
|---|---|
| “Toyofuta Industrial Park Entrance”, National Route 16 | About 3 min |
Visitor parking (41 spaces) is on the west side of the site, to the left of the building as seen from the road. Traffic on the site is one-way, so please use the left-hand entrance. The monthly contract spaces on the north side of the building are not available to visitors.
Products
We supply polymer particles designed around particle size, surface charge and function to meet the performance required of in vitro diagnostic reagents.
Latex particles (polystyrene)
Polystyrene nanoparticles for immunoturbidimetry (latex agglutination). The line-up covers particle sizes from 70 to 440 nm across a wide range of COOH charge densities, so that a grade can be selected to suit the antibody sensitisation conditions.
| No | Product | Typ. size (µm) | Typ. COOH charge density (mmol/g) |
|---|---|---|---|
| 1 | C080N | 0.08 | 0.18 |
| 2 | C090A | 0.09 | 0.31 |
| 3 | C090N | 0.09 | 0.16 |
| 4 | C100A | 0.10 | 0.14 |
| 5 | C150N | 0.15 | 0.10 |
| 6 | C150L | 0.16 | 0.07 |
| 7 | C180N | 0.19 | 0.08 |
| 8 | C190N | 0.19 | 0.08 |
| 9 | C200A | 0.20 | 0.08 |
| 10 | C270N | 0.27 | 0.05 |
| 11 | C400N | 0.42 | 0.03 |
| 12 | B120Z | 0.11 | — |
B120Z: “—” indicates a physical adsorption type.
Magnetic particles
Magnetic particles for chemiluminescent immunoassay (CLIA). They carry carboxyl groups and support direct antibody coupling as well as streptavidin (SA) immobilisation.
| Product | Surface | Typ. size (µm) | Typ. COOH charge density (µmol/g) | Typ. magnetic separation time (sec) | Typ. magnetic material content (%) |
|---|---|---|---|---|---|
| FS300C | Hydrophilic | 3.0 | 9 | 25 | 28 |
| FF240C | Hydrophobic | 2.4 | 15 | 30 | 34 |
| FS150C | Hydrophilic | 1.6 | 28 | 70 | 33 |
Coloured and fluorescent particles
Coloured and fluorescent latex particles for POCT and immunochromatography (lateral flow). They are designed to match the required colour or emission wavelength.
Contract development of qualitative and quantitative reagents
Contract development of qualitative and quantitative reagents using our own latex and magnetic particles. Drawing on our know-how in particle design, surface modification and reagent development, we propose a reagent design suited to your requirements.
Careers
We are hiring engineers to work on polymer particles for in vitro diagnostic reagents, from development through to commercial production.
Position
R&D and manufacturing — experienced professionals
Requirements
- Bachelor’s degree or above (Master’s or Ph.D. welcome)
- R&D experience in either ① or ② below
① Chemistry
- R&D experience with products related to polymer chemistry, organic synthesis or colloid chemistry
② Life sciences
- R&D experience with products related to biomolecules such as proteins or DNA
Preferred
- Research experience in polymerisation, particle design, or conjugation of particles with biomolecules
- Experience developing qualitative or quantitative reagents (ELISA, LIA, CLEIA and similar)
- Basic office software skills (Excel, Word)
The work
① Chemistry: development and manufacture of polymer particles
You will be responsible for the development, manufacture and evaluation of polymer particles used in in vitro diagnostic reagents and related fields.
The role covers the whole path from product design and synthesis to process development, quality assessment and scale-up.
Main responsibilities
- Design, synthesis, evaluation and improvement of polymer latex, magnetic particles and particles for chromatography columns
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
② Life sciences: conjugation technology for particles and biomolecules
You will develop and improve processes for conjugating our particles with biomolecules such as proteins and DNA, and develop research reagents.
The role spans the study of conjugation conditions, performance evaluation, process development and scale-up.
Main responsibilities
- Study and optimisation of conjugation conditions between our particles and biomolecules
- Design, evaluation and improvement of conjugation technology
- Development and performance evaluation of research reagents
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
Conditions
| Employment type | Permanent, full-time |
|---|---|
| Working hours | 9:00–18:00 (8 hours plus a 60-minute break; some flexibility) |
| Holidays | 120 days per year (two days off every week, Japanese public holidays, year-end / New Year period) |
| Paid leave | 10 days granted after six months of service, increasing to a maximum of 20 days |
| Salary review / bonus | Salary review once a year (April); bonus twice a year |
| Insurance | Health insurance, employees’ pension, employment insurance and workers’ compensation insurance |
| Overtime | Average overtime is approximately 10 hours per month. Overtime pay is paid in full. |
| Allowances | Commuting allowance and housing allowance (in accordance with company rules) |
| Probation | Three months in principle |
Position
R&D and manufacturing — entry-level / early-career
Requirements
- Bachelor’s degree or above (Master’s or Ph.D. welcome)
- An academic background in either ① or ② below
① Chemistry
- A major in polymer chemistry, organic synthesis or colloid chemistry
② Life sciences
- A major in biology, life science, agriculture, pharmaceutical science or a related field
Preferred
- University research in polymerisation, particle design, or conjugation of particles with biomolecules
- Basic knowledge of, or laboratory experience with, qualitative or quantitative reagents (ELISA, LIA, CLEIA and similar), including at university
- Basic office software skills (Excel, Word)
The work
① Chemistry: development and manufacture of polymer particles
You will be responsible for the development, manufacture and evaluation of polymer particles used in in vitro diagnostic reagents and related fields.
The role covers the whole path from product design and synthesis to process development, quality assessment and scale-up.
After joining, you will learn the work mainly through on-the-job training, supported by experienced colleagues.
Main responsibilities
- Design, synthesis, evaluation and improvement of polymer latex
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
② Life sciences: conjugation technology for particles and biomolecules
You will develop and improve processes for conjugating our particles with biomolecules such as proteins and DNA, and develop research reagents.
The role spans the study of conjugation conditions, performance evaluation, process development and scale-up.
After joining, you will learn the work mainly through on-the-job training, supported by experienced colleagues.
Main responsibilities
- Study and optimisation of conjugation conditions between our particles and biomolecules
- Design, evaluation and improvement of conjugation technology
- Development and performance evaluation of research reagents
- Process development and preparation of manufacturing and test procedures
- Operation of production equipment; recording and analysis of experimental data
- Design, execution and analysis of quality tests
- Improvement of product quality and manufacturing processes
- Scale-up towards commercial production
Conditions
| Employment type | Permanent, full-time |
|---|---|
| Working hours | 9:00–18:00 (8 hours plus a 60-minute break; some flexibility) |
| Holidays | 120 days per year (two days off every week, Japanese public holidays, year-end / New Year period) |
| Paid leave | 10 days granted after six months of service, increasing to a maximum of 20 days |
| Salary review / bonus | Salary review once a year (April); bonus twice a year |
| Insurance | Health insurance, employees’ pension, employment insurance and workers’ compensation insurance |
| Overtime | Average overtime is approximately 10 hours per month. Overtime pay is paid in full. |
| Allowances | Commuting allowance and housing allowance (in accordance with company rules) |
| Probation | Three months in principle |
R&D and production support
The work
- Support for R&D and production activities
- Quality testing and recording of experimental data
- Preparation and management of tools, equipment and materials
- Other work related to R&D and production
Preferred
- Knowledge of, or laboratory experience in, chemistry or the life sciences
- Basic office software skills (Excel, Word)
Administrative positions
The work
- Accounting, general affairs, HR, purchasing and sales administration
- Preparation and management of documents and data
- Handling telephone calls, email and visitors
- Other administrative work supporting company operations
Preferred
- Practical experience in accounting or other administrative work
- Basic office software skills (Excel, Word)
Conditions
Working days, hours, salary and other conditions are agreed individually, based on the role, your experience and your preferences.
Selection process
After reviewing your application, we will contact you with the outcome and, where applicable, an invitation to the first interview.
How to apply
Please send your CV and work history to the email address below. Japanese applicants are welcome to submit the standard Japanese resume (rirekisho) and work history (shokumu-keirekisho); a CV in the usual international format is equally acceptable. After reviewing your application, we will contact you about an interview.
Contact for recruitment: Tamori
Contact
We welcome enquiries about product specifications and technical questions, samples and quotations, OEM and custom development, purchasing and new business relationships, and recruitment.
Business hours: 9:00–18:00, Monday to Friday (Japan time). Closed on Japanese public holidays and during the year-end / New Year period.
For information on how we handle personal information, please see our Privacy Policy.
Privacy Policy
How we handle personal information.
ZOKK Co., Ltd. (“the Company”) handles the personal information entrusted to it by customers, business partners and job applicants appropriately, in accordance with the following policy.
1. Collection of personal information
The Company collects personal information such as names, company names, positions, contact details and the content of application documents by lawful and fair means, in the course of enquiries, business transactions and job applications.
2. Purpose of use
- Responding to enquiries and contacting you
- Communication regarding business transactions, and the conclusion and performance of contracts
- Providing information about the Company’s products and services
- Recruitment screening and related communication
Personal information of job applicants is used only for recruitment screening and related communication.
3. Provision to third parties
Except as required by law, the Company does not provide personal information to third parties without the consent of the individual concerned.
4. Outsourcing
The Company may outsource the handling of personal information to the extent necessary to achieve the purposes above. In such cases, the Company supervises the contractor necessarily and appropriately.
5. Security
The Company takes necessary and appropriate measures to prevent the leakage, loss or damage of personal information.
6. Requests for disclosure
Upon request by the individual concerned, the Company responds to requests for the disclosure, correction, suspension of use or deletion of retained personal data in accordance with applicable law, after verifying the identity of the requester.
7. Contact
ZOKK Co., Ltd. — Personal Information Enquiries
Representative Director: Kejun Fan
Room 601, Tokatsu Techno Plaza, 5-4-6 Kashiwanoha, Kashiwa, Chiba 277-0882, Japan
TEL +81-4-7128-7017 (Mon–Fri 9:00–18:00 JST)
MAIL zokk@zokkbio.com
8. Changes to this policy
The Company may revise this policy in response to changes in legislation or other circumstances. The revised policy takes effect when it is published on this page.
Established: 1 July 2026
Revised: 9 October 2026